Update history for 5.17.2 release

Bump version
Update TARGET file after changing buck template
2026-11-07 11:32:34 -05:00 · 2018-11-12 11:57:32 -08:00 · 2018-11-02 15:23:50 -07:00 · 2018-11-02 15:21:10 -07:00 · 2018-11-02 15:20:35 -07:00 · 2018-10-31 14:55:11 -07:00
232 changed files with 5399 additions and 1608 deletions
@@ -336,12 +336,18 @@ endif()

 # Used to run CI build and tests so we can run faster
 option(OPTDBG "Build optimized debug build with MSVC" OFF)
+option(WITH_RUNTIME_DEBUG "build with debug version of runtime library" ON)
 if(MSVC)
  if(OPTDBG)
    message(STATUS "Debug optimization is enabled")
-    set(CMAKE_CXX_FLAGS_DEBUG "/Oxt /${RUNTIME_LIBRARY}d")
+    set(CMAKE_CXX_FLAGS_DEBUG "/Oxt")
  else()
-    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /Od /RTC1 /Gm /${RUNTIME_LIBRARY}d")
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /Od /RTC1 /Gm")
+  endif()
+  if(WITH_RUNTIME_DEBUG)
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /${RUNTIME_LIBRARY}d")
+  else()
+    set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} /${RUNTIME_LIBRARY}")
  endif()
  set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} /Oxt /Zp8 /Gm- /Gy /${RUNTIME_LIBRARY}")

@@ -612,6 +618,7 @@ set(SOURCES
        utilities/blob_db/blob_compaction_filter.cc
        utilities/blob_db/blob_db.cc
        utilities/blob_db/blob_db_impl.cc
+        utilities/blob_db/blob_db_impl_filesnapshot.cc
        utilities/blob_db/blob_dump_tool.cc
        utilities/blob_db/blob_file.cc
        utilities/blob_db/blob_log_reader.cc
@@ -939,6 +946,7 @@ if(WITH_TESTS)
        util/hash_test.cc
        util/heap_test.cc
        util/rate_limiter_test.cc
+        util/repeatable_thread_test.cc
        util/slice_transform_test.cc
        util/timer_queue_test.cc
        util/thread_list_test.cc
@@ -981,6 +989,7 @@ if(WITH_TESTS)
  set(BENCHMARKS
    cache/cache_bench.cc
    memtable/memtablerep_bench.cc
+    db/range_del_aggregator_bench.cc
    tools/db_bench.cc
    table/table_reader_bench.cc
    utilities/column_aware_encoding_exp.cc
@@ -1,13 +1,50 @@
 # Rocksdb Change Log
-## Unreleased
-### Public API Change
-### New Features
+
+# 5.17.2 (10/24/2018)
 ### Bug Fixes
+* Fix the bug that WriteBatchWithIndex's SeekForPrev() doesn't see the entries with the same key.
+
+# 5.17.1 (10/16/2018)
+### Bug Fixes
+* Fix slow flush/compaction when DB contains many snapshots. The problem became noticeable to us in DBs with 100,000+ snapshots, though it will affect others at different thresholds.
+* Properly set the stop key for a truncated manual CompactRange
+* Fix corner case where a write group leader blocked due to write stall blocks other writers in queue with WriteOptions::no_slowdown set.
+
+### New Features
+* Introduced CacheAllocator, which lets the user specify custom allocator for memory in block cache.
+
+## 5.17.0 (10/05/2018)
+### Public API Change
+* `OnTableFileCreated` will now be called for empty files generated during compaction. In that case, `TableFileCreationInfo::file_path` will be "(nil)" and `TableFileCreationInfo::file_size` will be zero.
+* Add `FlushOptions::allow_write_stall`, which controls whether Flush calls start working immediately, even if it causes user writes to stall, or will wait until flush can be performed without causing write stall (similar to `CompactRangeOptions::allow_write_stall`). Note that the default value is false, meaning we add delay to Flush calls until stalling can be avoided when possible. This is behavior change compared to previous RocksDB versions, where Flush calls didn't check if they might cause stall or not.
+* Application using PessimisticTransactionDB is expected to rollback/commit recovered transactions before starting new ones. This assumption is used to skip concurrency control during recovery.
+
+### New Features
+* TransactionOptions::skip_concurrency_control allows pessimistic transactions to skip the overhead of concurrency control. Could be used for optimizing certain transactions or during recovery.
+
+### Bug Fixes
+* Avoid creating empty SSTs and subsequently deleting them in certain cases during compaction.
+* Sync CURRENT file contents during checkpoint.
+
+## 5.16.3 (10/1/2018)
+### Bug Fixes
+* Fix crash caused when `CompactFiles` run with `CompactionOptions::compression == CompressionType::kDisableCompressionOption`. Now that setting causes the compression type to be chosen according to the column family-wide compression options.
+
+## 5.16.2 (9/21/2018)
+### Bug Fixes
+* Fix bug in partition filters with format_version=4.
+
+## 5.16.1 (9/17/2018)
+### Bug Fixes
+* Remove trace_analyzer_tool from rocksdb_lib target in TARGETS file.
+* Fix RocksDB Java build and tests.
+* Remove sync point in Block destructor.

 ## 5.16.0 (8/21/2018)
 ### Public API Change
-* The merge operands are passed to `MergeOperator::ShouldMerge` in the reversed order relative to how they were merged (passed to FullMerge or FullMergeV2) for performance reasons 
+* The merge operands are passed to `MergeOperator::ShouldMerge` in the reversed order relative to how they were merged (passed to FullMerge or FullMergeV2) for performance reasons
 * GetAllKeyVersions() to take an extra argument of `max_num_ikeys`.
+* Using ZSTD dictionary trainer (i.e., setting `CompressionOptions::zstd_max_train_bytes` to a nonzero value) now requires ZSTD version 1.1.3 or later.

 ### New Features
 * Changes the format of index blocks by delta encoding the index values, which are the block handles. This saves the encoding of BlockHandle::offset of the non-head index entries in each restart interval. The feature is backward compatible but not forward compatible. It is disabled by default unless format_version 4 or above is used.
@@ -151,7 +188,8 @@
 * `BackupableDBOptions::max_valid_backups_to_open == 0` now means no backups will be opened during BackupEngine initialization. Previously this condition disabled limiting backups opened.
 * `DBOptions::preserve_deletes` is a new option that allows one to specify that DB should not drop tombstones for regular deletes if they have sequence number larger than what was set by the new API call `DB::SetPreserveDeletesSequenceNumber(SequenceNumber seqnum)`. Disabled by default.
 * API call `DB::SetPreserveDeletesSequenceNumber(SequenceNumber seqnum)` was added, users who wish to preserve deletes are expected to periodically call this function to advance the cutoff seqnum (all deletes made before this seqnum can be dropped by DB). It's user responsibility to figure out how to advance the seqnum in the way so the tombstones are kept for the desired period of time, yet are eventually processed in time and don't eat up too much space.
-* `ReadOptions::iter_start_seqnum` was added; if set to something > 0 user will see 2 changes in iterators behavior 1) only keys written with sequence larger than this parameter would be returned and 2) the `Slice` returned by iter->key() now points to the memory that keep User-oriented representation of the internal key, rather than user key. New struct `FullKey` was added to represent internal keys, along with a new helper function `ParseFullKey(const Slice& internal_key, FullKey* result);`.
+* `ReadOptions::iter_start_seqnum` was added;
+if set to something > 0 user will see 2 changes in iterators behavior 1) only keys written with sequence larger than this parameter would be returned and 2) the `Slice` returned by iter->key() now points to the memory that keep User-oriented representation of the internal key, rather than user key. New struct `FullKey` was added to represent internal keys, along with a new helper function `ParseFullKey(const Slice& internal_key, FullKey* result);`.
 * Deprecate trash_dir param in NewSstFileManager, right now we will rename deleted files to <name>.trash instead of moving them to trash directory
 * Allow setting a custom trash/DB size ratio limit in the SstFileManager, after which files that are to be scheduled for deletion are deleted immediately, regardless of any delete ratelimit.
 * Return an error on write if write_options.sync = true and write_options.disableWAL = true to warn user of inconsistent options. Previously we will not write to WAL and not respecting the sync options in this case.
@@ -533,6 +533,7 @@ TESTS = \
 	write_unprepared_transaction_test \
 	db_universal_compaction_test \
 	trace_analyzer_test \
+	repeatable_thread_test \

 PARALLEL_TEST = \
 	backupable_db_test \
@@ -582,7 +583,7 @@ TEST_LIBS = \
 	librocksdb_env_basic_test.a

 # TODO: add back forward_iterator_bench, after making it build in all environemnts.
-BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench column_aware_encoding_exp persistent_cache_bench
+BENCHMARKS = db_bench table_reader_bench cache_bench memtablerep_bench column_aware_encoding_exp persistent_cache_bench range_del_aggregator_bench

 # if user didn't config LIBNAME, set the default
 ifeq ($(LIBNAME),)
@@ -1002,8 +1003,10 @@ unity.a: unity.o
 	$(AM_V_AR)rm -f $@
 	$(AM_V_at)$(AR) $(ARFLAGS) $@ unity.o

+
+TOOLLIBOBJECTS = $(TOOL_LIB_SOURCES:.cc=.o)
 # try compiling db_test with unity
-unity_test: db/db_test.o db/db_test_util.o $(TESTHARNESS) unity.a
+unity_test: db/db_test.o db/db_test_util.o $(TESTHARNESS) $(TOOLLIBOBJECTS) unity.a
 	$(AM_LINK)
 	./unity_test

@@ -1548,9 +1551,15 @@ lua_test: utilities/lua/rocks_lua_test.o db/db_test_util.o $(LIBOBJECTS) $(TESTH
 range_del_aggregator_test: db/range_del_aggregator_test.o db/db_test_util.o $(LIBOBJECTS) $(TESTHARNESS)
 	$(AM_LINK)

+range_del_aggregator_bench: db/range_del_aggregator_bench.o $(LIBOBJECTS) $(TESTUTIL)
+	$(AM_LINK)
+
 blob_db_test: utilities/blob_db/blob_db_test.o $(LIBOBJECTS) $(TESTHARNESS)
 	$(AM_LINK)

+repeatable_thread_test: util/repeatable_thread_test.o $(LIBOBJECTS) $(TESTHARNESS)
+	$(AM_LINK)
+
 #-------------------------------------------------
 # make install related stuff
 INSTALL_PATH ?= /usr/local
@@ -1621,7 +1630,7 @@ ZLIB_SHA256 ?= c3e5e9fdd5004dcb542feda5ee4f0ff0744628baf8ed2dd5d66f8ca1197cb1a1
 ZLIB_DOWNLOAD_BASE ?= http://zlib.net
 BZIP2_VER ?= 1.0.6
 BZIP2_SHA256 ?= a2848f34fcd5d6cf47def00461fcb528a0484d8edef8208d6d2e2909dc61d9cd
-BZIP2_DOWNLOAD_BASE ?= http://www.bzip.org
+BZIP2_DOWNLOAD_BASE ?= https://web.archive.org/web/20180624184835/http://www.bzip.org
 SNAPPY_VER ?= 1.1.4
 SNAPPY_SHA256 ?= 134bfe122fd25599bb807bb8130e7ba6d9bdb851e0b16efcb83ac4f5d0b70057
 SNAPPY_DOWNLOAD_BASE ?= https://github.com/google/snappy/releases/download
@@ -1856,7 +1865,7 @@ $(java_libobjects): jl/%.o: %.cc
 rocksdbjava: $(java_all_libobjects)
 	$(AM_V_GEN)cd java;$(MAKE) javalib;
 	$(AM_V_at)rm -f ./java/target/$(ROCKSDBJNILIB)
-	$(AM_V_at)$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/target/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(java_libobjects) $(JAVA_LDFLAGS) $(COVERAGEFLAGS)
+	$(AM_V_at)$(CXX) $(CXXFLAGS) -I./java/. $(JAVA_INCLUDE) -shared -fPIC -o ./java/target/$(ROCKSDBJNILIB) $(JNI_NATIVE_SOURCES) $(java_all_libobjects) $(JAVA_LDFLAGS) $(COVERAGEFLAGS)
 	$(AM_V_at)cd java;jar -cf target/$(ROCKSDB_JAR) HISTORY*.md
 	$(AM_V_at)cd java/target;jar -uf $(ROCKSDB_JAR) $(ROCKSDBJNILIB)
 	$(AM_V_at)cd java/target/classes;jar -uf ../$(ROCKSDB_JAR) org/rocksdb/*.class org/rocksdb/util/*.class
@@ -1,3 +1,5 @@
+load("@fbcode_macros//build_defs:auto_headers.bzl", "AutoHeaders")
+
 REPO_PATH = package_name() + "/"

 BUCK_BINS = "buck-out/gen/" + REPO_PATH
@@ -195,7 +197,6 @@ cpp_library(
        "tools/ldb_cmd.cc",
        "tools/ldb_tool.cc",
        "tools/sst_dump_tool.cc",
-        "tools/trace_analyzer_tool.cc",
        "util/arena.cc",
        "util/auto_roll_logger.cc",
        "util/bloom.cc",
@@ -233,6 +234,7 @@ cpp_library(
        "utilities/blob_db/blob_compaction_filter.cc",
        "utilities/blob_db/blob_db.cc",
        "utilities/blob_db/blob_db_impl.cc",
+        "utilities/blob_db/blob_db_impl_filesnapshot.cc",
        "utilities/blob_db/blob_dump_tool.cc",
        "utilities/blob_db/blob_file.cc",
        "utilities/blob_db/blob_log_format.cc",
@@ -290,7 +292,7 @@ cpp_library(
        "utilities/write_batch_with_index/write_batch_with_index.cc",
        "utilities/write_batch_with_index/write_batch_with_index_internal.cc",
    ],
-    headers = AutoHeaders.RECURSIVE_GLOB,
+    auto_headers = AutoHeaders.RECURSIVE_GLOB,
    arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
    compiler_flags = rocksdb_compiler_flags,
    preprocessor_flags = rocksdb_preprocessor_flags,
@@ -303,6 +305,7 @@ cpp_library(
    srcs = [
        "db/db_test_util.cc",
        "table/mock_table.cc",
+        "tools/trace_analyzer_tool.cc",
        "util/fault_injection_test_env.cc",
        "util/testharness.cc",
        "util/testutil.cc",
@@ -311,7 +314,7 @@ cpp_library(
        "utilities/col_buf_encoder.cc",
        "utilities/column_aware_encoding_util.cc",
    ],
-    headers = AutoHeaders.RECURSIVE_GLOB,
+    auto_headers = AutoHeaders.RECURSIVE_GLOB,
    arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
    compiler_flags = rocksdb_compiler_flags,
    preprocessor_flags = rocksdb_preprocessor_flags,
@@ -323,9 +326,10 @@ cpp_library(
    name = "rocksdb_tools_lib",
    srcs = [
        "tools/db_bench_tool.cc",
+        "tools/trace_analyzer_tool.cc",
        "util/testutil.cc",
    ],
-    headers = AutoHeaders.RECURSIVE_GLOB,
+    auto_headers = AutoHeaders.RECURSIVE_GLOB,
    arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
    compiler_flags = rocksdb_compiler_flags,
    preprocessor_flags = rocksdb_preprocessor_flags,
@@ -336,7 +340,7 @@ cpp_library(
 cpp_library(
    name = "env_basic_test_lib",
    srcs = ["env/env_basic_test.cc"],
-    headers = AutoHeaders.RECURSIVE_GLOB,
+    auto_headers = AutoHeaders.RECURSIVE_GLOB,
    arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
    compiler_flags = rocksdb_compiler_flags,
    preprocessor_flags = rocksdb_preprocessor_flags,
@@ -376,11 +380,6 @@ ROCKS_TESTS = [
        "table/block_based_filter_block_test.cc",
        "serial",
    ],
-    [
-        "data_block_hash_index_test",
-        "table/data_block_hash_index_test.cc",
-        "serial",
-    ],
    [
        "block_test",
        "table/block_test.cc",
@@ -506,6 +505,11 @@ ROCKS_TESTS = [
        "table/cuckoo_table_reader_test.cc",
        "serial",
    ],
+    [
+        "data_block_hash_index_test",
+        "table/data_block_hash_index_test.cc",
+        "serial",
+    ],
    [
        "date_tiered_test",
        "utilities/date_tiered/date_tiered_test.cc",
@@ -931,6 +935,11 @@ ROCKS_TESTS = [
        "db/repair_test.cc",
        "serial",
    ],
+    [
+        "repeatable_thread_test",
+        "util/repeatable_thread_test.cc",
+        "serial",
+    ],
    [
        "sim_cache_test",
        "utilities/simulator_cache/sim_cache_test.cc",
@@ -956,11 +965,6 @@ ROCKS_TESTS = [
        "tools/sst_dump_test.cc",
        "serial",
    ],
-    [
-        "trace_analyzer_test",
-        "tools/trace_analyzer_test.cc",
-        "serial",
-    ],
    [
        "statistics_test",
        "monitoring/statistics_test.cc",
@@ -996,6 +1000,11 @@ ROCKS_TESTS = [
        "util/timer_queue_test.cc",
        "serial",
    ],
+    [
+        "trace_analyzer_test",
+        "tools/trace_analyzer_test.cc",
+        "serial",
+    ],
    [
        "transaction_test",
        "utilities/transactions/transaction_test.cc",
@@ -1078,19 +1087,19 @@ if not is_opt_mode:
        ttype = "gtest" if test_cfg[2] == "parallel" else "simple"
        test_bin = test_name + "_bin"

-        cpp_binary (
-          name = test_bin,
-          srcs = [test_cc],
-          deps = [":rocksdb_test_lib"],
-          preprocessor_flags = rocksdb_preprocessor_flags,
-          arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
-          compiler_flags = rocksdb_compiler_flags,
-          external_deps = rocksdb_external_deps,
+        cpp_binary(
+            name = test_bin,
+            srcs = [test_cc],
+            arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
+            compiler_flags = rocksdb_compiler_flags,
+            preprocessor_flags = rocksdb_preprocessor_flags,
+            deps = [":rocksdb_test_lib"],
+            external_deps = rocksdb_external_deps,
        )

        custom_unittest(
-          name = test_name,
-          type = ttype,
-          deps = [":" + test_bin],
-          command = [TEST_RUNNER, BUCK_BINS + test_bin]
+            name = test_name,
+            command = [TEST_RUNNER, BUCK_BINS + test_bin],
+            type = ttype,
+            deps = [":" + test_bin],
        )
@@ -12,6 +12,7 @@ At Facebook, we use RocksDB as storage engines in multiple data management servi
 6. LogDevice -- a distributed data store for logs [2]

 [1] https://research.facebook.com/publications/realtime-data-processing-at-facebook/
+
 [2] https://code.facebook.com/posts/357056558062811/logdevice-a-distributed-data-store-for-logs/

 ## LinkedIn
@@ -88,3 +89,6 @@ LzLabs is using RocksDB as a storage engine in their multi-database distributed

 ## ProfaneDB
 [ProfaneDB](https://profanedb.gitlab.io/) is a database for Protocol Buffers, and uses RocksDB for storage. It is accessible via gRPC, and the schema is defined using directly `.proto` files.
+
+## IOTA Foundation
+ [IOTA Foundation](https://www.iota.org/) is using RocksDB in the [IOTA Reference Implementation (IRI)](https://github.com/iotaledger/iri) to store the local state of the Tangle. The Tangle is the first open-source distributed ledger powering the future of the Internet of Things.
@@ -109,12 +109,14 @@ def generate_targets(repo_path):
        "rocksdb_test_lib",
        src_mk.get("MOCK_LIB_SOURCES", []) +
        src_mk.get("TEST_LIB_SOURCES", []) +
-        src_mk.get("EXP_LIB_SOURCES", []),
+        src_mk.get("EXP_LIB_SOURCES", []) +
+        src_mk.get("ANALYZER_LIB_SOURCES", []),
        [":rocksdb_lib"])
    # rocksdb_tools_lib
    TARGETS.add_library(
        "rocksdb_tools_lib",
        src_mk.get("BENCH_LIB_SOURCES", []) +
+        src_mk.get("ANALYZER_LIB_SOURCES", []) +
        ["util/testutil.cc"],
        [":rocksdb_lib"])

@@ -10,7 +10,7 @@ def pretty_list(lst, indent=8):

    if len(lst) == 1:
        return "\"%s\"" % lst[0]
-    
+
    separator = "\",\n%s\"" % (" " * indent)
    res = separator.join(sorted(lst))
    res = "\n" + (" " * indent) + "\"" + res + "\",\n" + (" " * (indent - 4))
@@ -31,13 +31,16 @@ class TARGETSBuilder:
        self.targets_file.close()

    def add_library(self, name, srcs, deps=None, headers=None):
+        headers_attr_prefix = ""
        if headers is None:
+            headers_attr_prefix = "auto_"
            headers = "AutoHeaders.RECURSIVE_GLOB"
-        self.targets_file.write(targets_cfg.library_template % (
-            name,
-            pretty_list(srcs),
-            headers,
-            pretty_list(deps)))
+        self.targets_file.write(targets_cfg.library_template.format(
+            name=name,
+            srcs=pretty_list(srcs),
+            headers_attr_prefix=headers_attr_prefix,
+            headers=headers,
+            deps=pretty_list(deps)))
        self.total_lib = self.total_lib + 1

    def add_binary(self, name, srcs, deps=None):
@@ -2,7 +2,9 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 from __future__ import unicode_literals
-rocksdb_target_header = """REPO_PATH = package_name() + "/"
+rocksdb_target_header = """load("@fbcode_macros//build_defs:auto_headers.bzl", "AutoHeaders")
+
+REPO_PATH = package_name() + "/"

 BUCK_BINS = "buck-out/gen/" + REPO_PATH

@@ -73,13 +75,13 @@ if is_opt_mode:

 library_template = """
 cpp_library(
-    name = "%s",
-    srcs = [%s],
-    headers = %s,
+    name = "{name}",
+    srcs = [{srcs}],
+    {headers_attr_prefix}headers = {headers},
    arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
    compiler_flags = rocksdb_compiler_flags,
    preprocessor_flags = rocksdb_preprocessor_flags,
-    deps = [%s],
+    deps = [{deps}],
    external_deps = rocksdb_external_deps,
 )
 """
@@ -118,21 +120,20 @@ if not is_opt_mode:
        ttype = "gtest" if test_cfg[2] == "parallel" else "simple"
        test_bin = test_name + "_bin"

-        cpp_binary (
-          name = test_bin,
-          srcs = [test_cc],
-          deps = [":rocksdb_test_lib"],
-          preprocessor_flags = rocksdb_preprocessor_flags,
-          arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
-          compiler_flags = rocksdb_compiler_flags,
-          external_deps = rocksdb_external_deps,
+        cpp_binary(
+            name = test_bin,
+            srcs = [test_cc],
+            arch_preprocessor_flags = rocksdb_arch_preprocessor_flags,
+            compiler_flags = rocksdb_compiler_flags,
+            preprocessor_flags = rocksdb_preprocessor_flags,
+            deps = [":rocksdb_test_lib"],
+            external_deps = rocksdb_external_deps,
        )

        custom_unittest(
-          name = test_name,
-          type = ttype,
-          deps = [":" + test_bin],
-          command = [TEST_RUNNER, BUCK_BINS + test_bin]
+            name = test_name,
+            command = [TEST_RUNNER, BUCK_BINS + test_bin],
+            type = ttype,
+            deps = [":" + test_bin],
        )
-
 """
@@ -121,8 +121,8 @@ Status BuildTable(
      file->SetIOPriority(io_priority);
      file->SetWriteLifeTimeHint(write_hint);

-      file_writer.reset(new WritableFileWriter(std::move(file), env_options,
-                                               ioptions.statistics));
+      file_writer.reset(new WritableFileWriter(
+          std::move(file), fname, env_options, ioptions.statistics));
      builder = NewTableBuilder(
          ioptions, mutable_cf_options, internal_comparator,
          int_tbl_prop_collector_factories, column_family_id,
@@ -33,6 +33,7 @@
 #include "rocksdb/utilities/backupable_db.h"
 #include "rocksdb/utilities/checkpoint.h"
 #include "rocksdb/utilities/db_ttl.h"
+#include "rocksdb/utilities/memory_util.h"
 #include "rocksdb/utilities/optimistic_transaction_db.h"
 #include "rocksdb/utilities/transaction.h"
 #include "rocksdb/utilities/transaction_db.h"
@@ -41,6 +42,10 @@
 #include "rocksdb/perf_context.h"
 #include "utilities/merge_operators.h"

+#include <vector>
+#include <unordered_set>
+#include <map>
+
 using rocksdb::BytewiseComparator;
 using rocksdb::Cache;
 using rocksdb::ColumnFamilyDescriptor;
@@ -108,8 +113,12 @@ using rocksdb::TransactionLogIterator;
 using rocksdb::BatchResult;
 using rocksdb::PerfLevel;
 using rocksdb::PerfContext;
+using rocksdb::MemoryUtil;

 using std::shared_ptr;
+using std::vector;
+using std::unordered_set;
+using std::map;

 extern "C" {

@@ -2402,7 +2411,7 @@ void rocksdb_options_set_bytes_per_sync(

 void rocksdb_options_set_writable_file_max_buffer_size(rocksdb_options_t* opt,
                                                       uint64_t v) {
-  opt->rep.writable_file_max_buffer_size = v;
+  opt->rep.writable_file_max_buffer_size = static_cast<size_t>(v);
 }

 void rocksdb_options_set_allow_concurrent_memtable_write(rocksdb_options_t* opt,
@@ -2433,11 +2442,13 @@ void rocksdb_options_set_max_write_buffer_number_to_maintain(
  opt->rep.max_write_buffer_number_to_maintain = n;
 }

-void rocksdb_options_set_enable_pipelined_write(rocksdb_options_t* opt, unsigned char v) {
+void rocksdb_options_set_enable_pipelined_write(rocksdb_options_t* opt,
+                                                unsigned char v) {
  opt->rep.enable_pipelined_write = v;
 }

-void rocksdb_options_set_max_subcompactions(rocksdb_options_t* opt, uint32_t n) {
+void rocksdb_options_set_max_subcompactions(rocksdb_options_t* opt,
+                                            uint32_t n) {
  opt->rep.max_subcompactions = n;
 }

@@ -4099,6 +4110,98 @@ const char* rocksdb_pinnableslice_value(const rocksdb_pinnableslice_t* v,
  *vlen = v->rep.size();
  return v->rep.data();
 }
+
+// container to keep databases and caches in order to use rocksdb::MemoryUtil
+struct rocksdb_memory_consumers_t {
+  std::vector<rocksdb_t*> dbs;
+  std::unordered_set<rocksdb_cache_t*> caches;
+};
+
+// initializes new container of memory consumers
+rocksdb_memory_consumers_t* rocksdb_memory_consumers_create() {
+  return new rocksdb_memory_consumers_t;
+}
+
+// adds datatabase to the container of memory consumers
+void rocksdb_memory_consumers_add_db(rocksdb_memory_consumers_t* consumers,
+                                     rocksdb_t* db) {
+  consumers->dbs.push_back(db);
+}
+
+// adds cache to the container of memory consumers
+void rocksdb_memory_consumers_add_cache(rocksdb_memory_consumers_t* consumers,
+                                        rocksdb_cache_t* cache) {
+  consumers->caches.insert(cache);
+}
+
+// deletes container with memory consumers
+void rocksdb_memory_consumers_destroy(rocksdb_memory_consumers_t* consumers) {
+  delete consumers;
+}
+
+// contains memory usage statistics provided by rocksdb::MemoryUtil
+struct rocksdb_memory_usage_t {
+  uint64_t mem_table_total;
+  uint64_t mem_table_unflushed;
+  uint64_t mem_table_readers_total;
+  uint64_t cache_total;
+};
+
+// estimates amount of memory occupied by consumers (dbs and caches)
+rocksdb_memory_usage_t* rocksdb_approximate_memory_usage_create(
+    rocksdb_memory_consumers_t* consumers, char** errptr) {
+
+  vector<DB*> dbs;
+  for (auto db : consumers->dbs) {
+    dbs.push_back(db->rep);
+  }
+
+  unordered_set<const Cache*> cache_set;
+  for (auto cache : consumers->caches) {
+    cache_set.insert(const_cast<const Cache*>(cache->rep.get()));
+  }
+
+  std::map<rocksdb::MemoryUtil::UsageType, uint64_t> usage_by_type;
+
+  auto status = MemoryUtil::GetApproximateMemoryUsageByType(dbs, cache_set,
+                                                            &usage_by_type);
+  if (SaveError(errptr, status)) {
+    return nullptr;
+  }
+
+  auto result = new rocksdb_memory_usage_t;
+  result->mem_table_total = usage_by_type[MemoryUtil::kMemTableTotal];
+  result->mem_table_unflushed = usage_by_type[MemoryUtil::kMemTableUnFlushed];
+  result->mem_table_readers_total = usage_by_type[MemoryUtil::kTableReadersTotal];
+  result->cache_total = usage_by_type[MemoryUtil::kCacheTotal];
+  return result;
+}
+
+uint64_t rocksdb_approximate_memory_usage_get_mem_table_total(
+    rocksdb_memory_usage_t* memory_usage) {
+  return memory_usage->mem_table_total;
+}
+
+uint64_t rocksdb_approximate_memory_usage_get_mem_table_unflushed(
+    rocksdb_memory_usage_t* memory_usage) {
+  return memory_usage->mem_table_unflushed;
+}
+
+uint64_t rocksdb_approximate_memory_usage_get_mem_table_readers_total(
+    rocksdb_memory_usage_t* memory_usage) {
+  return memory_usage->mem_table_readers_total;
+}
+
+uint64_t rocksdb_approximate_memory_usage_get_cache_total(
+    rocksdb_memory_usage_t* memory_usage) {
+  return memory_usage->cache_total;
+}
+
+// deletes container with memory usage estimates
+void rocksdb_approximate_memory_usage_destroy(rocksdb_memory_usage_t* usage) {
+  delete usage;
+}
+
 }  // end extern "C"

 #endif  // !ROCKSDB_LITE
@@ -19,11 +19,8 @@

 // Can not use port/port.h macros as this is a c file
 #ifdef OS_WIN
-
 #include <windows.h>

-#define snprintf _snprintf
-
 // Ok for uniqueness
 int geteuid() {
  int result = 0;
@@ -34,6 +31,11 @@ int geteuid() {
  return result;
 }

+// VS < 2015
+#if defined(_MSC_VER) && (_MSC_VER < 1900)
+#define snprintf _snprintf
+#endif
+
 #endif

 const char* phase = "";
@@ -47,12 +49,19 @@ static void StartPhase(const char* name) {
  fprintf(stderr, "=== Test %s\n", name);
  phase = name;
 }
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning (disable: 4996) // getenv security warning
+#endif
 static const char* GetTempDir(void) {
    const char* ret = getenv("TEST_TMPDIR");
    if (ret == NULL || ret[0] == '\0')
        ret = "/tmp";
    return ret;
 }
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif

 #define CheckNoError(err)                                               \
  if ((err) != NULL) {                                                  \
@@ -643,7 +652,7 @@ int main(int argc, char** argv) {
    rocksdb_sstfilewriter_t* writer =
        rocksdb_sstfilewriter_create(env_opt, io_options);

-    unlink(sstfilename);
+    remove(sstfilename);
    rocksdb_sstfilewriter_open(writer, sstfilename, &err);
    CheckNoError(err);
    rocksdb_sstfilewriter_put(writer, "sstk1", 5, "v1", 2, &err);
@@ -664,7 +673,7 @@ int main(int argc, char** argv) {
    CheckGet(db, roptions, "sstk2", "v2");
    CheckGet(db, roptions, "sstk3", "v3");

-    unlink(sstfilename);
+    remove(sstfilename);
    rocksdb_sstfilewriter_open(writer, sstfilename, &err);
    CheckNoError(err);
    rocksdb_sstfilewriter_put(writer, "sstk2", 5, "v4", 2, &err);
@@ -1334,6 +1343,47 @@ int main(int argc, char** argv) {
    rocksdb_destroy_db(options, dbname, &err);
  }

+  // Check memory usage stats
+  StartPhase("approximate_memory_usage");
+  {
+    // Create database
+    db = rocksdb_open(options, dbname, &err);
+    CheckNoError(err);
+
+    rocksdb_memory_consumers_t* consumers;
+    consumers = rocksdb_memory_consumers_create();
+    rocksdb_memory_consumers_add_db(consumers, db);
+    rocksdb_memory_consumers_add_cache(consumers, cache);
+
+    // take memory usage report before write-read operation
+    rocksdb_memory_usage_t* mu1;
+    mu1 = rocksdb_approximate_memory_usage_create(consumers, &err);
+    CheckNoError(err);
+
+    // Put data (this should affect memtables)
+    rocksdb_put(db, woptions, "memory", 6, "test", 4, &err);
+    CheckNoError(err);
+    CheckGet(db, roptions, "memory", "test");
+
+    // take memory usage report after write-read operation
+    rocksdb_memory_usage_t* mu2;
+    mu2 = rocksdb_approximate_memory_usage_create(consumers, &err);
+    CheckNoError(err);
+
+    // amount of memory used within memtables should grow
+    CheckCondition(rocksdb_approximate_memory_usage_get_mem_table_total(mu2) >=
+                   rocksdb_approximate_memory_usage_get_mem_table_total(mu1));
+    CheckCondition(rocksdb_approximate_memory_usage_get_mem_table_unflushed(mu2) >=
+                   rocksdb_approximate_memory_usage_get_mem_table_unflushed(mu1));
+
+    rocksdb_memory_consumers_destroy(consumers);
+    rocksdb_approximate_memory_usage_destroy(mu1);
+    rocksdb_approximate_memory_usage_destroy(mu2);
+    rocksdb_close(db);
+    rocksdb_destroy_db(options, dbname, &err);
+    CheckNoError(err);
+  }
+
  StartPhase("cuckoo_options");
  {
    rocksdb_cuckoo_table_options_t* cuckoo_options;
@@ -1675,7 +1725,7 @@ int main(int argc, char** argv) {
    db = rocksdb_open(options, dbname, &err);
    CheckNoError(err);
  }
-  
+
  StartPhase("cleanup");
  rocksdb_close(db);
  rocksdb_options_destroy(options);
@@ -308,6 +308,55 @@ TEST_F(CompactFilesTest, CompactionFilterWithGetSv) {
  delete db;
 }

+TEST_F(CompactFilesTest, SentinelCompressionType) {
+  if (!Zlib_Supported()) {
+    fprintf(stderr, "zlib compression not supported, skip this test\n");
+    return;
+  }
+  if (!Snappy_Supported()) {
+    fprintf(stderr, "snappy compression not supported, skip this test\n");
+    return;
+  }
+  // Check that passing `CompressionType::kDisableCompressionOption` to
+  // `CompactFiles` causes it to use the column family compression options.
+  for (auto compaction_style :
+       {CompactionStyle::kCompactionStyleLevel,
+        CompactionStyle::kCompactionStyleUniversal,
+        CompactionStyle::kCompactionStyleNone}) {
+    DestroyDB(db_name_, Options());
+    Options options;
+    options.compaction_style = compaction_style;
+    // L0: Snappy, L1: ZSTD, L2: Snappy
+    options.compression_per_level = {CompressionType::kSnappyCompression,
+                                     CompressionType::kZlibCompression,
+                                     CompressionType::kSnappyCompression};
+    options.create_if_missing = true;
+    FlushedFileCollector* collector = new FlushedFileCollector();
+    options.listeners.emplace_back(collector);
+    DB* db = nullptr;
+    ASSERT_OK(DB::Open(options, db_name_, &db));
+
+    db->Put(WriteOptions(), "key", "val");
+    db->Flush(FlushOptions());
+
+    auto l0_files = collector->GetFlushedFiles();
+    ASSERT_EQ(1, l0_files.size());
+
+    // L0->L1 compaction, so output should be ZSTD-compressed
+    CompactionOptions compaction_opts;
+    compaction_opts.compression = CompressionType::kDisableCompressionOption;
+    ASSERT_OK(db->CompactFiles(compaction_opts, l0_files, 1));
+
+    rocksdb::TablePropertiesCollection all_tables_props;
+    ASSERT_OK(db->GetPropertiesOfAllTables(&all_tables_props));
+    for (const auto& name_and_table_props : all_tables_props) {
+      ASSERT_EQ(CompressionTypeToString(CompressionType::kZlibCompression),
+                name_and_table_props.second->compression_name);
+    }
+    delete db;
+  }
+}
+
 }  // namespace rocksdb

 int main(int argc, char** argv) {
@@ -25,22 +25,12 @@ CompactedDBImpl::~CompactedDBImpl() {
 }

 size_t CompactedDBImpl::FindFile(const Slice& key) {
-  size_t left = 0;
  size_t right = files_.num_files - 1;
-  while (left < right) {
-    size_t mid = (left + right) >> 1;
-    const FdWithKeyRange& f = files_.files[mid];
-    if (user_comparator_->Compare(ExtractUserKey(f.largest_key), key) < 0) {
-      // Key at "mid.largest" is < "target".  Therefore all
-      // files at or before "mid" are uninteresting.
-      left = mid + 1;
-    } else {
-      // Key at "mid.largest" is >= "target".  Therefore all files
-      // after "mid" are uninteresting.
-      right = mid;
-    }
-  }
-  return right;
+  auto cmp = [&](const FdWithKeyRange& f, const Slice& k) -> bool {
+    return user_comparator_->Compare(ExtractUserKey(f.largest_key), k) < 0;
+  };
+  return static_cast<size_t>(std::lower_bound(files_.files,
+                            files_.files + right, key, cmp) - files_.files);
 }

 Status CompactedDBImpl::Get(const ReadOptions& options, ColumnFamilyHandle*,
@@ -18,8 +18,8 @@ CompactionIterator::CompactionIterator(
    SequenceNumber earliest_write_conflict_snapshot,
    const SnapshotChecker* snapshot_checker, Env* env,
    bool report_detailed_time, bool expect_valid_internal_key,
-    RangeDelAggregator* range_del_agg,
-    const Compaction* compaction, const CompactionFilter* compaction_filter,
+    RangeDelAggregator* range_del_agg, const Compaction* compaction,
+    const CompactionFilter* compaction_filter,
    const std::atomic<bool>* shutting_down,
    const SequenceNumber preserve_deletes_seqnum)
    : CompactionIterator(
@@ -77,6 +77,12 @@ CompactionIterator::CompactionIterator(
    earliest_snapshot_ = snapshots_->at(0);
    latest_snapshot_ = snapshots_->back();
  }
+#ifndef NDEBUG
+  // findEarliestVisibleSnapshot assumes this ordering.
+  for (size_t i = 1; i < snapshots_->size(); ++i) {
+    assert(snapshots_->at(i - 1) <= snapshots_->at(i));
+  }
+#endif
  if (compaction_filter_ != nullptr) {
    if (compaction_filter_->IgnoreSnapshots()) {
      ignore_snapshots_ = true;
@@ -505,6 +511,31 @@ void CompactionIterator::NextFromInput() {
        ++iter_stats_.num_optimized_del_drop_obsolete;
      }
      input_->Next();
+    } else if ((ikey_.type == kTypeDeletion) && bottommost_level_ &&
+               ikeyNotNeededForIncrementalSnapshot()) {
+      // Handle the case where we have a delete key at the bottom most level
+      // We can skip outputting the key iff there are no subsequent puts for this
+      // key
+      ParsedInternalKey next_ikey;
+      input_->Next();
+      // Skip over all versions of this key that happen to occur in the same snapshot
+      // range as the delete
+      while (input_->Valid() &&
+             ParseInternalKey(input_->key(), &next_ikey) &&
+             cmp_->Equal(ikey_.user_key, next_ikey.user_key) &&
+             (prev_snapshot == 0 || next_ikey.sequence > prev_snapshot ||
+              (snapshot_checker_ != nullptr &&
+               UNLIKELY(!snapshot_checker_->IsInSnapshot(next_ikey.sequence,
+                                                         prev_snapshot))))) {
+        input_->Next();
+      }
+      // If you find you still need to output a row with this key, we need to output the
+      // delete too
+      if (input_->Valid() && ParseInternalKey(input_->key(), &next_ikey) &&
+          cmp_->Equal(ikey_.user_key, next_ikey.user_key)) {
+        valid_ = true;
+        at_next_ = true;
+      }
    } else if (ikey_.type == kTypeMerge) {
      if (!merge_helper_->HasOperator()) {
        status_ = Status::InvalidArgument(
@@ -603,18 +634,23 @@ void CompactionIterator::PrepareOutput() {
 inline SequenceNumber CompactionIterator::findEarliestVisibleSnapshot(
    SequenceNumber in, SequenceNumber* prev_snapshot) {
  assert(snapshots_->size());
-  SequenceNumber prev = kMaxSequenceNumber;
-  for (const auto cur : *snapshots_) {
-    assert(prev == kMaxSequenceNumber || prev <= cur);
-    if (cur >= in && (snapshot_checker_ == nullptr ||
-                      snapshot_checker_->IsInSnapshot(in, cur))) {
-      *prev_snapshot = prev == kMaxSequenceNumber ? 0 : prev;
+  auto snapshots_iter = std::lower_bound(
+      snapshots_->begin(), snapshots_->end(), in);
+  if (snapshots_iter == snapshots_->begin()) {
+    *prev_snapshot = 0;
+  } else {
+    *prev_snapshot = *std::prev(snapshots_iter);
+    assert(*prev_snapshot < in);
+  }
+  for (; snapshots_iter != snapshots_->end(); ++snapshots_iter) {
+    auto cur = *snapshots_iter;
+    assert(in <= cur);
+    if (snapshot_checker_ == nullptr ||
+        snapshot_checker_->IsInSnapshot(in, cur)) {
      return cur;
    }
-    prev = cur;
-    assert(prev < kMaxSequenceNumber);
+    *prev_snapshot = cur;
  }
-  *prev_snapshot = prev;
  return kMaxSequenceNumber;
 }

@@ -247,9 +247,8 @@ class CompactionIteratorTest : public testing::TestWithParam<bool> {
    c_iter_.reset(new CompactionIterator(
        iter_.get(), cmp_, merge_helper_.get(), last_sequence, &snapshots_,
        earliest_write_conflict_snapshot, snapshot_checker_.get(),
-        Env::Default(), false /* report_detailed_time */,
-        false, range_del_agg_.get(), std::move(compaction), filter,
-        &shutting_down_));
+        Env::Default(), false /* report_detailed_time */, false,
+        range_del_agg_.get(), std::move(compaction), filter, &shutting_down_));
  }

  void AddSnapshot(SequenceNumber snapshot,
@@ -672,8 +671,12 @@ TEST_P(CompactionIteratorTest, ZeroOutSequenceAtBottomLevel) {
 TEST_P(CompactionIteratorTest, RemoveDeletionAtBottomLevel) {
  AddSnapshot(1);
  RunTest({test::KeyStr("a", 1, kTypeDeletion),
-           test::KeyStr("b", 2, kTypeDeletion)},
-          {"", ""}, {test::KeyStr("b", 2, kTypeDeletion)}, {""},
+           test::KeyStr("b", 3, kTypeDeletion),
+           test::KeyStr("b", 1, kTypeValue)},
+          {"", "", ""},
+          {test::KeyStr("b", 3, kTypeDeletion),
+           test::KeyStr("b", 0, kTypeValue)},
+          {"", ""},
          kMaxSequenceNumber /*last_commited_seq*/, nullptr /*merge_operator*/,
          nullptr /*compaction_filter*/, true /*bottommost_level*/);
 }
@@ -842,13 +845,26 @@ TEST_F(CompactionIteratorWithSnapshotCheckerTest,
      {test::KeyStr("a", 1, kTypeDeletion), test::KeyStr("b", 2, kTypeDeletion),
       test::KeyStr("c", 3, kTypeDeletion)},
      {"", "", ""},
-      {test::KeyStr("b", 2, kTypeDeletion),
-       test::KeyStr("c", 3, kTypeDeletion)},
+      {},
      {"", ""}, kMaxSequenceNumber /*last_commited_seq*/,
      nullptr /*merge_operator*/, nullptr /*compaction_filter*/,
      true /*bottommost_level*/);
 }

+TEST_F(CompactionIteratorWithSnapshotCheckerTest,
+       NotRemoveDeletionIfValuePresentToEarlierSnapshot) {
+  AddSnapshot(2,1);
+  RunTest(
+      {test::KeyStr("a", 4, kTypeDeletion), test::KeyStr("a", 1, kTypeValue),
+          test::KeyStr("b", 3, kTypeValue)},
+      {"", "", ""},
+      {test::KeyStr("a", 4, kTypeDeletion), test::KeyStr("a", 0, kTypeValue),
+            test::KeyStr("b", 3, kTypeValue)},
+      {"", "", ""}, kMaxSequenceNumber /*last_commited_seq*/,
+      nullptr /*merge_operator*/, nullptr /*compaction_filter*/,
+      true /*bottommost_level*/);
+}
+
 TEST_F(CompactionIteratorWithSnapshotCheckerTest,
       NotRemoveSingleDeletionIfNotVisibleToEarliestSnapshot) {
  AddSnapshot(2, 1);
@@ -593,10 +593,6 @@ Status CompactionJob::Run() {
    thread.join();
  }

-  if (output_directory_) {
-    output_directory_->Fsync();
-  }
-
  compaction_stats_.micros = env_->NowMicros() - start_micros;
  MeasureTime(stats_, COMPACTION_TIME, compaction_stats_.micros);

@@ -611,6 +607,10 @@ Status CompactionJob::Run() {
    }
  }

+  if (status.ok() && output_directory_) {
+    status = output_directory_->Fsync();
+  }
+
  if (status.ok()) {
    thread_pool.clear();
    std::vector<const FileMetaData*> files_meta;
@@ -1077,7 +1077,8 @@ void CompactionJob::ProcessKeyValueCompaction(SubcompactionState* sub_compact) {
  }

  if (status.ok() && sub_compact->builder == nullptr &&
-      sub_compact->outputs.size() == 0) {
+      sub_compact->outputs.size() == 0 &&
+      !range_del_agg->IsEmpty()) {
    // handle subcompaction containing only range deletions
    status = OpenCompactionOutputFile(sub_compact);
  }
@@ -1308,9 +1309,7 @@ Status CompactionJob::FinishCompactionOutputFile(
    // VersionEdit.
    assert(!sub_compact->outputs.empty());
    sub_compact->outputs.pop_back();
-    sub_compact->builder.reset();
-    sub_compact->current_output_file_size = 0;
-    return s;
+    meta = nullptr;
  }

  if (s.ok() && (current_entries > 0 || tp.num_range_deletions > 0)) {
@@ -1464,8 +1463,9 @@ Status CompactionJob::OpenCompactionOutputFile(
  writable_file->SetWriteLifeTimeHint(write_hint_);
  writable_file->SetPreallocationBlockSize(static_cast<size_t>(
      sub_compact->compaction->OutputFilePreallocationSize()));
-  sub_compact->outfile.reset(new WritableFileWriter(
-      std::move(writable_file), env_options_, db_options_.statistics.get()));
+  sub_compact->outfile.reset(
+      new WritableFileWriter(std::move(writable_file), fname, env_options_,
+                             db_options_.statistics.get()));

  // If the Column family flag is to only optimize filters for hits,
  // we can skip creating filters if this is the bottommost_level where
@@ -79,7 +79,7 @@ class CompactionJobTest : public testing::Test {
        shutting_down_(false),
        preserve_deletes_seqnum_(0),
        mock_table_factory_(new mock::MockTableFactory()),
-        error_handler_(db_options_, &mutex_) {
+        error_handler_(nullptr, db_options_, &mutex_) {
    EXPECT_OK(env_->CreateDirIfMissing(dbname_));
    db_options_.db_paths.emplace_back(dbname_,
                                      std::numeric_limits<uint64_t>::max());
@@ -205,7 +205,7 @@ class CompactionJobTest : public testing::Test {
        manifest, &file, env_->OptimizeForManifestWrite(env_options_));
    ASSERT_OK(s);
    unique_ptr<WritableFileWriter> file_writer(
-        new WritableFileWriter(std::move(file), env_options_));
+        new WritableFileWriter(std::move(file), manifest, env_options_));
    {
      log::Writer log(std::move(file_writer), 0, false);
      std::string record;
@@ -49,7 +49,7 @@ bool FindIntraL0Compaction(const std::vector<FileMetaData*>& level_files,
  // increasing.
  size_t new_compact_bytes_per_del_file = 0;
  for (span_len = 1; span_len < level_files.size(); ++span_len) {
-    compact_bytes += level_files[span_len]->fd.file_size;
+    compact_bytes += static_cast<size_t>(level_files[span_len]->fd.file_size);
    new_compact_bytes_per_del_file = compact_bytes / span_len;
    if (level_files[span_len]->being_compacted ||
        new_compact_bytes_per_del_file > compact_bytes_per_del_file) {
@@ -219,7 +219,8 @@ void CompactionPicker::GetRange(const std::vector<CompactionInputFiles>& inputs,

 bool CompactionPicker::ExpandInputsToCleanCut(const std::string& /*cf_name*/,
                                              VersionStorageInfo* vstorage,
-                                              CompactionInputFiles* inputs) {
+                                              CompactionInputFiles* inputs,
+                                              InternalKey** next_smallest) {
  // This isn't good compaction
  assert(!inputs->empty());

@@ -242,7 +243,8 @@ bool CompactionPicker::ExpandInputsToCleanCut(const std::string& /*cf_name*/,
    GetRange(*inputs, &smallest, &largest);
    inputs->clear();
    vstorage->GetOverlappingInputs(level, &smallest, &largest, &inputs->files,
-                                   hint_index, &hint_index);
+                                   hint_index, &hint_index, true,
+                                   next_smallest);
  } while (inputs->size() > old_size);

  // we started off with inputs non-empty and the previous loop only grew
@@ -315,13 +317,29 @@ Compaction* CompactionPicker::CompactFiles(
  // shouldn't have been released since.
  assert(!FilesRangeOverlapWithCompaction(input_files, output_level));

-  auto c =
-      new Compaction(vstorage, ioptions_, mutable_cf_options, input_files,
-                     output_level, compact_options.output_file_size_limit,
-                     mutable_cf_options.max_compaction_bytes, output_path_id,
-                     compact_options.compression, ioptions_.compression_opts,
-                     compact_options.max_subcompactions,
-                     /* grandparents */ {}, true);
+  CompressionType compression_type;
+  if (compact_options.compression == kDisableCompressionOption) {
+    int base_level;
+    if (ioptions_.compaction_style == kCompactionStyleLevel) {
+      base_level = vstorage->base_level();
+    } else {
+      base_level = 1;
+    }
+    compression_type =
+        GetCompressionType(ioptions_, vstorage, mutable_cf_options,
+                           output_level, base_level);
+  } else {
+    // TODO(ajkr): `CompactionOptions` offers configurable `CompressionType`
+    // without configurable `CompressionOptions`, which is inconsistent.
+    compression_type = compact_options.compression;
+  }
+  auto c = new Compaction(
+      vstorage, ioptions_, mutable_cf_options, input_files, output_level,
+      compact_options.output_file_size_limit,
+      mutable_cf_options.max_compaction_bytes, output_path_id, compression_type,
+      GetCompressionOptions(ioptions_, vstorage, output_level),
+      compact_options.max_subcompactions,
+      /* grandparents */ {}, true);
  RegisterCompaction(c);
  return c;
 }
@@ -633,7 +651,6 @@ Compaction* CompactionPicker::CompactRange(
      uint64_t s = inputs[i]->compensated_file_size;
      total += s;
      if (total >= limit) {
-        **compaction_end = inputs[i + 1]->smallest;
        covering_the_whole_range = false;
        inputs.files.resize(i + 1);
        break;
@@ -642,7 +659,10 @@ Compaction* CompactionPicker::CompactRange(
  }
  assert(output_path_id < static_cast<uint32_t>(ioptions_.cf_paths.size()));

-  if (ExpandInputsToCleanCut(cf_name, vstorage, &inputs) == false) {
+  InternalKey key_storage;
+  InternalKey* next_smallest = &key_storage;
+  if (ExpandInputsToCleanCut(cf_name, vstorage, &inputs, &next_smallest) ==
+      false) {
    // manual compaction is now multi-threaded, so it can
    // happen that ExpandWhileOverlapping fails
    // we handle it higher in RunManualCompaction
@@ -650,8 +670,10 @@ Compaction* CompactionPicker::CompactRange(
    return nullptr;
  }

-  if (covering_the_whole_range) {
+  if (covering_the_whole_range || !next_smallest) {
    *compaction_end = nullptr;
+  } else {
+    **compaction_end = *next_smallest;
  }

  CompactionInputFiles output_level_inputs;
@@ -151,7 +151,8 @@ class CompactionPicker {
  // Will return false if it is impossible to apply this compaction.
  bool ExpandInputsToCleanCut(const std::string& cf_name,
                              VersionStorageInfo* vstorage,
-                              CompactionInputFiles* inputs);
+                              CompactionInputFiles* inputs,
+                              InternalKey** next_smallest = nullptr);

  // Returns true if any one of the parent files are being compacted
  bool IsRangeInCompaction(VersionStorageInfo* vstorage,
@@ -22,11 +22,12 @@ class DBBloomFilterTest : public DBTestBase {

 class DBBloomFilterTestWithParam
    : public DBTestBase,
-      public testing::WithParamInterface<std::tuple<bool, bool>> {
+      public testing::WithParamInterface<std::tuple<bool, bool, uint32_t>> {
  //                             public testing::WithParamInterface<bool> {
 protected:
  bool use_block_based_filter_;
  bool partition_filters_;
+  uint32_t format_version_;

 public:
  DBBloomFilterTestWithParam() : DBTestBase("/db_bloom_filter_tests") {}
@@ -36,9 +37,12 @@ class DBBloomFilterTestWithParam
  void SetUp() override {
    use_block_based_filter_ = std::get<0>(GetParam());
    partition_filters_ = std::get<1>(GetParam());
+    format_version_ = std::get<2>(GetParam());
  }
 };

+class DBBloomFilterTestDefFormatVersion : public DBBloomFilterTestWithParam {};
+
 class SliceTransformLimitedDomainGeneric : public SliceTransform {
  const char* Name() const override {
    return "SliceTransformLimitedDomainGeneric";
@@ -62,7 +66,7 @@ class SliceTransformLimitedDomainGeneric : public SliceTransform {
 // KeyMayExist can lead to a few false positives, but not false negatives.
 // To make test deterministic, use a much larger number of bits per key-20 than
 // bits in the key, so that false positives are eliminated
-TEST_P(DBBloomFilterTestWithParam, KeyMayExist) {
+TEST_P(DBBloomFilterTestDefFormatVersion, KeyMayExist) {
  do {
    ReadOptions ropts;
    std::string value;
@@ -401,6 +405,11 @@ TEST_P(DBBloomFilterTestWithParam, BloomFilter) {
      table_options.index_type =
          BlockBasedTableOptions::IndexType::kTwoLevelIndexSearch;
    }
+    table_options.format_version = format_version_;
+    if (format_version_ >= 4) {
+      // value delta encoding challenged more with index interval > 1
+      table_options.index_block_restart_interval = 8;
+    }
    table_options.metadata_block_size = 32;
    options.table_factory.reset(NewBlockBasedTableFactory(table_options));

@@ -456,10 +465,26 @@ TEST_P(DBBloomFilterTestWithParam, BloomFilter) {
  } while (ChangeCompactOptions());
 }

-INSTANTIATE_TEST_CASE_P(DBBloomFilterTestWithParam, DBBloomFilterTestWithParam,
-                        ::testing::Values(std::make_tuple(true, false),
-                                          std::make_tuple(false, true),
-                                          std::make_tuple(false, false)));
+INSTANTIATE_TEST_CASE_P(
+    FormatDef, DBBloomFilterTestDefFormatVersion,
+    ::testing::Values(std::make_tuple(true, false, test::kDefaultFormatVersion),
+                      std::make_tuple(false, true, test::kDefaultFormatVersion),
+                      std::make_tuple(false, false,
+                                      test::kDefaultFormatVersion)));
+
+INSTANTIATE_TEST_CASE_P(
+    FormatDef, DBBloomFilterTestWithParam,
+    ::testing::Values(std::make_tuple(true, false, test::kDefaultFormatVersion),
+                      std::make_tuple(false, true, test::kDefaultFormatVersion),
+                      std::make_tuple(false, false,
+                                      test::kDefaultFormatVersion)));
+
+INSTANTIATE_TEST_CASE_P(
+    FormatLatest, DBBloomFilterTestWithParam,
+    ::testing::Values(std::make_tuple(true, false, test::kLatestFormatVersion),
+                      std::make_tuple(false, true, test::kLatestFormatVersion),
+                      std::make_tuple(false, false,
+                                      test::kLatestFormatVersion)));

 TEST_F(DBBloomFilterTest, BloomFilterRate) {
  while (ChangeFilterOptions()) {
@@ -116,6 +116,21 @@ private:
  std::vector<std::atomic<int>> compaction_completed_;
 };

+class SstStatsCollector : public EventListener {
+ public:
+  SstStatsCollector() : num_ssts_creation_started_(0) {}
+
+  void OnTableFileCreationStarted(
+      const TableFileCreationBriefInfo& /* info */) override {
+    ++num_ssts_creation_started_;
+  }
+
+  int num_ssts_creation_started() { return num_ssts_creation_started_; }
+
+ private:
+  std::atomic<int> num_ssts_creation_started_;
+};
+
 static const int kCDTValueSize = 1000;
 static const int kCDTKeysPerBuffer = 4;
 static const int kCDTNumLevels = 8;
@@ -2462,6 +2477,7 @@ TEST_P(DBCompactionTestWithParam, ManualLevelCompactionOutputPathId) {

    // Compaction range overlaps files
    Compact(1, "p1", "p9", 1);
+    ASSERT_OK(dbfull()->TEST_WaitForCompact());
    ASSERT_EQ("0,1", FilesPerLevel(1));
    ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
    ASSERT_EQ(0, GetSstFileCount(options.db_paths[0].path));
@@ -2477,6 +2493,7 @@ TEST_P(DBCompactionTestWithParam, ManualLevelCompactionOutputPathId) {

    // Compact just the new range
    Compact(1, "b", "f", 1);
+    ASSERT_OK(dbfull()->TEST_WaitForCompact());
    ASSERT_EQ("0,2", FilesPerLevel(1));
    ASSERT_EQ(2, GetSstFileCount(options.db_paths[1].path));
    ASSERT_EQ(0, GetSstFileCount(options.db_paths[0].path));
@@ -2493,6 +2510,7 @@ TEST_P(DBCompactionTestWithParam, ManualLevelCompactionOutputPathId) {
    compact_options.target_path_id = 1;
    compact_options.exclusive_manual_compaction = exclusive_manual_compaction_;
    db_->CompactRange(compact_options, handles_[1], nullptr, nullptr);
+    ASSERT_OK(dbfull()->TEST_WaitForCompact());

    ASSERT_EQ("0,1", FilesPerLevel(1));
    ASSERT_EQ(1, GetSstFileCount(options.db_paths[1].path));
@@ -3485,12 +3503,13 @@ TEST_F(DBCompactionTest, CompactRangeDelayedByL0FileCount) {
      // ensure the auto compaction doesn't finish until manual compaction has
      // had a chance to be delayed.
      rocksdb::SyncPoint::GetInstance()->LoadDependency(
-          {{"DBImpl::CompactRange:StallWait", "CompactionJob::Run():End"}});
+          {{"DBImpl::WaitUntilFlushWouldNotStallWrites:StallWait",
+            "CompactionJob::Run():End"}});
    } else {
      // ensure the auto-compaction doesn't finish until manual compaction has
      // continued without delay.
      rocksdb::SyncPoint::GetInstance()->LoadDependency(
-          {{"DBImpl::CompactRange:StallWaitDone", "CompactionJob::Run():End"}});
+          {{"DBImpl::FlushMemTable:StallWaitDone", "CompactionJob::Run():End"}});
    }
    rocksdb::SyncPoint::GetInstance()->EnableProcessing();

@@ -3538,12 +3557,13 @@ TEST_F(DBCompactionTest, CompactRangeDelayedByImmMemTableCount) {
      // ensure the flush doesn't finish until manual compaction has had a
      // chance to be delayed.
      rocksdb::SyncPoint::GetInstance()->LoadDependency(
-          {{"DBImpl::CompactRange:StallWait", "FlushJob::WriteLevel0Table"}});
+          {{"DBImpl::WaitUntilFlushWouldNotStallWrites:StallWait",
+            "FlushJob::WriteLevel0Table"}});
    } else {
      // ensure the flush doesn't finish until manual compaction has continued
      // without delay.
      rocksdb::SyncPoint::GetInstance()->LoadDependency(
-          {{"DBImpl::CompactRange:StallWaitDone",
+          {{"DBImpl::FlushMemTable:StallWaitDone",
            "FlushJob::WriteLevel0Table"}});
    }
    rocksdb::SyncPoint::GetInstance()->EnableProcessing();
@@ -3553,6 +3573,7 @@ TEST_F(DBCompactionTest, CompactRangeDelayedByImmMemTableCount) {
      ASSERT_OK(Put(Key(0), RandomString(&rnd, 1024)));
      FlushOptions flush_opts;
      flush_opts.wait = false;
+      flush_opts.allow_write_stall = true;
      dbfull()->Flush(flush_opts);
    }

@@ -3588,7 +3609,7 @@ TEST_F(DBCompactionTest, CompactRangeShutdownWhileDelayed) {
    // The auto-compaction waits until the manual compaction finishes to ensure
    // the signal comes from closing CF/DB, not from compaction making progress.
    rocksdb::SyncPoint::GetInstance()->LoadDependency(
-        {{"DBImpl::CompactRange:StallWait",
+        {{"DBImpl::WaitUntilFlushWouldNotStallWrites:StallWait",
          "DBCompactionTest::CompactRangeShutdownWhileDelayed:PreShutdown"},
         {"DBCompactionTest::CompactRangeShutdownWhileDelayed:PostManual",
          "CompactionJob::Run():End"}});
@@ -3639,18 +3660,21 @@ TEST_F(DBCompactionTest, CompactRangeSkipFlushAfterDelay) {
  // began. So it unblocks CompactRange and precludes its flush. Throughout the
  // test, stall conditions are upheld via high L0 file count.
  rocksdb::SyncPoint::GetInstance()->LoadDependency(
-      {{"DBImpl::CompactRange:StallWait",
+      {{"DBImpl::WaitUntilFlushWouldNotStallWrites:StallWait",
        "DBCompactionTest::CompactRangeSkipFlushAfterDelay:PreFlush"},
       {"DBCompactionTest::CompactRangeSkipFlushAfterDelay:PostFlush",
-        "DBImpl::CompactRange:StallWaitDone"},
-       {"DBImpl::CompactRange:StallWaitDone", "CompactionJob::Run():End"}});
+        "DBImpl::FlushMemTable:StallWaitDone"},
+       {"DBImpl::FlushMemTable:StallWaitDone", "CompactionJob::Run():End"}});
  rocksdb::SyncPoint::GetInstance()->EnableProcessing();

+  //used for the delayable flushes
+  FlushOptions flush_opts;
+  flush_opts.allow_write_stall = true;
  for (int i = 0; i < kNumL0FilesLimit - 1; ++i) {
    for (int j = 0; j < 2; ++j) {
      ASSERT_OK(Put(Key(j), RandomString(&rnd, 1024)));
    }
-    Flush();
+    dbfull()->Flush(flush_opts);
  }
  auto manual_compaction_thread = port::Thread([this]() {
    CompactRangeOptions cro;
@@ -3660,7 +3684,7 @@ TEST_F(DBCompactionTest, CompactRangeSkipFlushAfterDelay) {

  TEST_SYNC_POINT("DBCompactionTest::CompactRangeSkipFlushAfterDelay:PreFlush");
  Put(ToString(0), RandomString(&rnd, 1024));
-  Flush();
+  dbfull()->Flush(flush_opts);
  Put(ToString(0), RandomString(&rnd, 1024));
  TEST_SYNC_POINT("DBCompactionTest::CompactRangeSkipFlushAfterDelay:PostFlush");
  manual_compaction_thread.join();
@@ -3816,6 +3840,30 @@ TEST_F(DBCompactionTest, CompactFilesOutputRangeConflict) {
  bg_thread.join();
 }

+TEST_F(DBCompactionTest, CompactionHasEmptyOutput) {
+  Options options = CurrentOptions();
+  SstStatsCollector* collector = new SstStatsCollector();
+  options.level0_file_num_compaction_trigger = 2;
+  options.listeners.emplace_back(collector);
+  Reopen(options);
+
+  // Make sure the L0 files overlap to prevent trivial move.
+  ASSERT_OK(Put("a", "val"));
+  ASSERT_OK(Put("b", "val"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Delete("a"));
+  ASSERT_OK(Delete("b"));
+  ASSERT_OK(Flush());
+
+  dbfull()->TEST_WaitForCompact();
+  ASSERT_EQ(NumTableFilesAtLevel(0), 0);
+  ASSERT_EQ(NumTableFilesAtLevel(1), 0);
+
+  // Expect one file creation to start for each flush, and zero for compaction
+  // since no keys are written.
+  ASSERT_EQ(2, collector->num_ssts_creation_started());
+}
+
 INSTANTIATE_TEST_CASE_P(DBCompactionTestWithParam, DBCompactionTestWithParam,
                        ::testing::Values(std::make_tuple(1, true),
                                          std::make_tuple(1, false),
@@ -3913,6 +3961,50 @@ INSTANTIATE_TEST_CASE_P(
                      CompactionPri::kOldestSmallestSeqFirst,
                      CompactionPri::kMinOverlappingRatio));

+class NoopMergeOperator : public MergeOperator {
+ public:
+  NoopMergeOperator() {}
+
+  virtual bool FullMergeV2(const MergeOperationInput& /*merge_in*/,
+                           MergeOperationOutput* merge_out) const override {
+    std::string val("bar");
+    merge_out->new_value = val;
+    return true;
+  }
+
+  virtual const char* Name() const override { return "Noop"; }
+};
+
+TEST_F(DBCompactionTest, PartialManualCompaction) {
+  Options opts = CurrentOptions();
+  opts.num_levels = 3;
+  opts.level0_file_num_compaction_trigger = 10;
+  opts.compression = kNoCompression;
+  opts.merge_operator.reset(new NoopMergeOperator());
+  opts.target_file_size_base = 10240;
+  DestroyAndReopen(opts);
+
+  Random rnd(301);
+  for (auto i = 0; i < 8; ++i) {
+    for (auto j = 0; j < 10; ++j) {
+      Merge("foo", RandomString(&rnd, 1024));
+    }
+    Flush();
+  }
+
+  MoveFilesToLevel(2);
+
+  std::string prop;
+  EXPECT_TRUE(dbfull()->GetProperty(DB::Properties::kLiveSstFilesSize, &prop));
+  uint64_t max_compaction_bytes = atoi(prop.c_str()) / 2;
+  ASSERT_OK(dbfull()->SetOptions(
+      {{"max_compaction_bytes", std::to_string(max_compaction_bytes)}}));
+
+  CompactRangeOptions cro;
+  cro.bottommost_level_compaction = BottommostLevelCompaction::kForce;
+  dbfull()->CompactRange(cro, nullptr, nullptr);
+}
+
 #endif // !defined(ROCKSDB_LITE)
 }  // namespace rocksdb

@@ -35,6 +35,7 @@ TEST_F(DBFlushTest, FlushWhileWritingManifest) {
  Reopen(options);
  FlushOptions no_wait;
  no_wait.wait = false;
+  no_wait.allow_write_stall=true;

  SyncPoint::GetInstance()->LoadDependency(
      {{"VersionSet::LogAndApply:WriteManifest",
@@ -215,9 +215,11 @@ DBImpl::DBImpl(const DBOptions& options, const std::string& dbname,
      // requires a custom gc for compaction, we use that to set use_custom_gc_
      // as well.
      use_custom_gc_(seq_per_batch),
+      shutdown_initiated_(false),
+      own_sfm_(options.sst_file_manager == nullptr),
      preserve_deletes_(options.preserve_deletes),
      closed_(false),
-      error_handler_(immutable_db_options_, &mutex_) {
+      error_handler_(this, immutable_db_options_, &mutex_) {
  // !batch_per_trx_ implies seq_per_batch_ because it is only unset for
  // WriteUnprepared, which should use seq_per_batch_.
  assert(batch_per_txn_ || seq_per_batch_);
@@ -259,16 +261,62 @@ Status DBImpl::Resume() {
    return Status::OK();
  }

-  Status s = error_handler_.GetBGError();
-  if (s.severity() > Status::Severity::kHardError) {
+  if (error_handler_.IsRecoveryInProgress()) {
+    // Don't allow a mix of manual and automatic recovery
+    return Status::Busy();
+  }
+
+  mutex_.Unlock();
+  Status s = error_handler_.RecoverFromBGError(true);
+  mutex_.Lock();
+  return s;
+}
+
+// This function implements the guts of recovery from a background error. It
+// is eventually called for both manual as well as automatic recovery. It does
+// the following -
+// 1. Wait for currently scheduled background flush/compaction to exit, in
+//    order to inadvertently causing an error and thinking recovery failed
+// 2. Flush memtables if there's any data for all the CFs. This may result
+//    another error, which will be saved by error_handler_ and reported later
+//    as the recovery status
+// 3. Find and delete any obsolete files
+// 4. Schedule compactions if needed for all the CFs. This is needed as the
+//    flush in the prior step might have been a no-op for some CFs, which
+//    means a new super version wouldn't have been installed
+Status DBImpl::ResumeImpl() {
+  mutex_.AssertHeld();
+  WaitForBackgroundWork();
+
+  Status bg_error = error_handler_.GetBGError();
+  Status s;
+  if (shutdown_initiated_) {
+    // Returning shutdown status to SFM during auto recovery will cause it
+    // to abort the recovery and allow the shutdown to progress
+    s = Status::ShutdownInProgress();
+  }
+  if (s.ok() && bg_error.severity() > Status::Severity::kHardError) {
    ROCKS_LOG_INFO(immutable_db_options_.info_log,
        "DB resume requested but failed due to Fatal/Unrecoverable error");
-    return s;
+    s = bg_error;
+  }
+
+  // We cannot guarantee consistency of the WAL. So force flush Memtables of
+  // all the column families
+  if (s.ok()) {
+    s = FlushAllCFs(FlushReason::kErrorRecovery);
+    if (!s.ok()) {
+      ROCKS_LOG_INFO(immutable_db_options_.info_log,
+                     "DB resume requested but failed due to Flush failure [%s]",
+                     s.ToString().c_str());
+    }
  }

  JobContext job_context(0);
  FindObsoleteFiles(&job_context, true);
-  error_handler_.ClearBGError();
+  if (s.ok()) {
+    s = error_handler_.ClearBGError();
+  }
  mutex_.Unlock();

  job_context.manifest_file_number = 1;
@@ -277,13 +325,36 @@ Status DBImpl::Resume() {
  }
  job_context.Clean();

-  ROCKS_LOG_INFO(immutable_db_options_.info_log, "Successfully resumed DB");
+  if (s.ok()) {
+    ROCKS_LOG_INFO(immutable_db_options_.info_log, "Successfully resumed DB");
+  }
  mutex_.Lock();
-  MaybeScheduleFlushOrCompaction();
+  // Check for shutdown again before scheduling further compactions,
+  // since we released and re-acquired the lock above
+  if (shutdown_initiated_) {
+    s = Status::ShutdownInProgress();
+  }
+  if (s.ok()) {
+    for (auto cfd : *versions_->GetColumnFamilySet()) {
+      SchedulePendingCompaction(cfd);
+    }
+    MaybeScheduleFlushOrCompaction();
+  }
+
+  // Wake up any waiters - in this case, it could be the shutdown thread
+  bg_cv_.SignalAll();

  // No need to check BGError again. If something happened, event listener would be
  // notified and the operation causing it would have failed
-  return Status::OK();
+  return s;
+}
+
+void DBImpl::WaitForBackgroundWork() {
+  // Wait for background work to finish
+  while (bg_bottom_compaction_scheduled_ || bg_compaction_scheduled_ ||
+         bg_flush_scheduled_) {
+    bg_cv_.Wait();
+  }
 }

 // Will lock the mutex_,  will wait for completion if wait is true
@@ -313,14 +384,20 @@ void DBImpl::CancelAllBackgroundWork(bool wait) {
  if (!wait) {
    return;
  }
-  // Wait for background work to finish
-  while (bg_bottom_compaction_scheduled_ || bg_compaction_scheduled_ ||
-         bg_flush_scheduled_) {
-    bg_cv_.Wait();
-  }
+  WaitForBackgroundWork();
 }

 Status DBImpl::CloseHelper() {
+  // Guarantee that there is no background error recovery in progress before
+  // continuing with the shutdown
+  mutex_.Lock();
+  shutdown_initiated_ = true;
+  error_handler_.CancelErrorRecovery();
+  while (error_handler_.IsRecoveryInProgress()) {
+    bg_cv_.Wait();
+  }
+  mutex_.Unlock();
+
  // CancelAllBackgroundWork called with false means we just set the shutdown
  // marker. After this we do a variant of the waiting and unschedule work
  // (to consider: moving all the waiting into CancelAllBackgroundWork(true))
@@ -338,7 +415,8 @@ Status DBImpl::CloseHelper() {
  // Wait for background work to finish
  while (bg_bottom_compaction_scheduled_ || bg_compaction_scheduled_ ||
         bg_flush_scheduled_ || bg_purge_scheduled_ ||
-         pending_purge_obsolete_files_) {
+         pending_purge_obsolete_files_ ||
+         error_handler_.IsRecoveryInProgress()) {
    TEST_SYNC_POINT("DBImpl::~DBImpl:WaitJob");
    bg_cv_.Wait();
  }
@@ -348,9 +426,12 @@ Status DBImpl::CloseHelper() {
  flush_scheduler_.Clear();

  while (!flush_queue_.empty()) {
-    auto cfd = PopFirstFromFlushQueue();
-    if (cfd->Unref()) {
-      delete cfd;
+    const FlushRequest& flush_req = PopFirstFromFlushQueue();
+    for (const auto& iter : flush_req) {
+      ColumnFamilyData* cfd = iter.first;
+      if (cfd->Unref()) {
+        delete cfd;
+      }
    }
  }
  while (!compaction_queue_.empty()) {
@@ -440,6 +521,17 @@ Status DBImpl::CloseHelper() {
  ROCKS_LOG_INFO(immutable_db_options_.info_log, "Shutdown complete");
  LogFlush(immutable_db_options_.info_log);

+#ifndef ROCKSDB_LITE
+  // If the sst_file_manager was allocated by us during DB::Open(), ccall
+  // Close() on it before closing the info_log. Otherwise, background thread
+  // in SstFileManagerImpl might try to log something
+  if (immutable_db_options_.sst_file_manager && own_sfm_) {
+    auto sfm = static_cast<SstFileManagerImpl*>(
+        immutable_db_options_.sst_file_manager.get());
+    sfm->Close();
+  }
+#endif // ROCKSDB_LITE
+
  if (immutable_db_options_.info_log && own_info_log_) {
    Status s = immutable_db_options_.info_log->Close();
    if (ret.ok()) {
@@ -2410,7 +2502,7 @@ Status DBImpl::GetDbIdentity(std::string& identity) const {
  if (!s.ok()) {
    return s;
  }
-  char* buffer = reinterpret_cast<char*>(alloca(file_size));
+  char* buffer = reinterpret_cast<char*>(alloca(static_cast<size_t>(file_size)));
  Slice id;
  s = id_file_reader->Read(static_cast<size_t>(file_size), &id, buffer);
  if (!s.ok()) {
@@ -3143,7 +3235,8 @@ Status DBImpl::TraceIteratorSeek(const uint32_t& cf_id, const Slice& key) {
  return s;
 }

-Status DBImpl::TraceIteratorSeekForPrev(const uint32_t& cf_id, const Slice& key) {
+Status DBImpl::TraceIteratorSeekForPrev(const uint32_t& cf_id,
+                                        const Slice& key) {
  Status s;
  if (tracer_) {
    InstrumentedMutexLock lock(&trace_mutex_);
@@ -22,9 +22,9 @@
 #include "db/column_family.h"
 #include "db/compaction_job.h"
 #include "db/dbformat.h"
-#include "db/external_sst_file_ingestion_job.h"
 #include "db/error_handler.h"
 #include "db/event_helpers.h"
+#include "db/external_sst_file_ingestion_job.h"
 #include "db/flush_job.h"
 #include "db/flush_scheduler.h"
 #include "db/internal_stats.h"
@@ -396,7 +396,7 @@ class DBImpl : public DB {
  Status TEST_SwitchMemtable(ColumnFamilyData* cfd = nullptr);

  // Force current memtable contents to be flushed.
-  Status TEST_FlushMemTable(bool wait = true,
+  Status TEST_FlushMemTable(bool wait = true, bool allow_write_stall = false,
                            ColumnFamilyHandle* cfh = nullptr);

  // Wait for memtable compaction
@@ -464,6 +464,7 @@ class DBImpl : public DB {

  int TEST_BGCompactionsAllowed() const;
  int TEST_BGFlushesAllowed() const;
+  size_t TEST_GetWalPreallocateBlockSize(uint64_t write_buffer_size) const;

 #endif  // NDEBUG

@@ -795,6 +796,7 @@ class DBImpl : public DB {

 private:
  friend class DB;
+  friend class ErrorHandler;
  friend class InternalStats;
  friend class PessimisticTransaction;
  friend class TransactionBaseImpl;
@@ -811,6 +813,7 @@ class DBImpl : public DB {
  friend struct SuperVersion;
  friend class CompactedDBImpl;
  friend class DBTest_ConcurrentFlushWAL_Test;
+  friend class DBTest_MixedSlowdownOptionsStop_Test;
 #ifndef NDEBUG
  friend class DBTest2_ReadCallbackTest_Test;
  friend class WriteCallbackTest_WriteWithCallbackTest_Test;
@@ -845,6 +848,8 @@ class DBImpl : public DB {
                 bool read_only = false, bool error_if_log_file_exist = false,
                 bool error_if_data_exists_in_logs = false);

+  Status ResumeImpl();
+
  void MaybeIgnoreError(Status* s) const;

  const Status CreateArchivalDirectory();
@@ -884,12 +889,41 @@ class DBImpl : public DB {
  Status SyncClosedLogs(JobContext* job_context);

  // Flush the in-memory write buffer to storage.  Switches to a new
-  // log-file/memtable and writes a new descriptor iff successful.
+  // log-file/memtable and writes a new descriptor iff successful. Then
+  // installs a new super version for the column family.
  Status FlushMemTableToOutputFile(ColumnFamilyData* cfd,
                                   const MutableCFOptions& mutable_cf_options,
                                   bool* madeProgress, JobContext* job_context,
+                                   SuperVersionContext* superversion_context,
                                   LogBuffer* log_buffer);

+  // Argument required by background flush thread.
+  struct BGFlushArg {
+    BGFlushArg()
+        : cfd_(nullptr), memtable_id_(0), superversion_context_(nullptr) {}
+    BGFlushArg(ColumnFamilyData* cfd, uint64_t memtable_id,
+               SuperVersionContext* superversion_context)
+        : cfd_(cfd),
+          memtable_id_(memtable_id),
+          superversion_context_(superversion_context) {}
+
+    // Column family to flush.
+    ColumnFamilyData* cfd_;
+    // Maximum ID of memtable to flush. In this column family, memtables with
+    // IDs smaller than this value must be flushed before this flush completes.
+    uint64_t memtable_id_;
+    // Pointer to a SuperVersionContext object. After flush completes, RocksDB
+    // installs a new superversion for the column family. This operation
+    // requires a SuperVersionContext object (currently embedded in JobContext).
+    SuperVersionContext* superversion_context_;
+  };
+
+  // Flush the memtables of (multiple) column families to multiple files on
+  // persistent storage.
+  Status FlushMemTablesToOutputFiles(
+      const autovector<BGFlushArg>& bg_flush_args, bool* made_progress,
+      JobContext* job_context, LogBuffer* log_buffer);
+
  // REQUIRES: log_numbers are sorted in ascending order
  Status RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
                         SequenceNumber* next_sequence, bool read_only);
@@ -902,6 +936,12 @@ class DBImpl : public DB {
  Status WriteLevel0TableForRecovery(int job_id, ColumnFamilyData* cfd,
                                     MemTable* mem, VersionEdit* edit);

+  // Restore alive_log_files_ and total_log_size_ after recovery.
+  // It needs to run only when there's no flush during recovery
+  // (e.g. avoid_flush_during_recovery=true). May also trigger flush
+  // in case total_log_size > max_total_wal_size.
+  Status RestoreAliveLogFiles(const std::vector<uint64_t>& log_numbers);
+
  // num_bytes: for slowdown case, delay time is calculated based on
  //            `num_bytes` going through.
  Status DelayWrite(uint64_t num_bytes, const WriteOptions& write_options);
@@ -911,19 +951,28 @@ class DBImpl : public DB {

  Status ScheduleFlushes(WriteContext* context);

-  Status SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
-                        FlushReason flush_reason = FlushReason::kOthers);
+  Status SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context);

  // Force current memtable contents to be flushed.
  Status FlushMemTable(ColumnFamilyData* cfd, const FlushOptions& options,
                       FlushReason flush_reason, bool writes_stopped = false);

+  // Wait until flushing this column family won't stall writes
+  Status WaitUntilFlushWouldNotStallWrites(ColumnFamilyData* cfd,
+                                           bool* flush_needed);
+
  // Wait for memtable flushed.
  // If flush_memtable_id is non-null, wait until the memtable with the ID
  // gets flush. Otherwise, wait until the column family don't have any
  // memtable pending flush.
  Status WaitForFlushMemTable(ColumnFamilyData* cfd,
-                              const uint64_t* flush_memtable_id = nullptr);
+                              const uint64_t* flush_memtable_id = nullptr) {
+    return WaitForFlushMemTables({cfd}, {flush_memtable_id});
+  }
+  // Wait for memtables to be flushed for multiple column families.
+  Status WaitForFlushMemTables(
+      const autovector<ColumnFamilyData*>& cfds,
+      const autovector<const uint64_t*>& flush_memtable_ids);

  // REQUIRES: mutex locked
  Status SwitchWAL(WriteContext* write_context);
@@ -979,7 +1028,17 @@ class DBImpl : public DB {
  ColumnFamilyData* GetColumnFamilyDataByName(const std::string& cf_name);

  void MaybeScheduleFlushOrCompaction();
-  void SchedulePendingFlush(ColumnFamilyData* cfd, FlushReason flush_reason);
+
+  // A flush request specifies the column families to flush as well as the
+  // largest memtable id to persist for each column family. Once all the
+  // memtables whose IDs are smaller than or equal to this per-column-family
+  // specified value, this flush request is considered to have completed its
+  // work of flushing this column family. After completing the work for all
+  // column families in this request, this flush is considered complete.
+  typedef std::vector<std::pair<ColumnFamilyData*, uint64_t>> FlushRequest;
+
+  void SchedulePendingFlush(const FlushRequest& req, FlushReason flush_reason);
+
  void SchedulePendingCompaction(ColumnFamilyData* cfd);
  void SchedulePendingPurge(std::string fname, std::string dir_to_sync,
                            FileType type, uint64_t number, int job_id);
@@ -998,9 +1057,10 @@ class DBImpl : public DB {
                              LogBuffer* log_buffer,
                              PrepickedCompaction* prepicked_compaction);
  Status BackgroundFlush(bool* madeProgress, JobContext* job_context,
-                         LogBuffer* log_buffer);
+                         LogBuffer* log_buffer, FlushReason* reason);

-  bool EnoughRoomForCompaction(const std::vector<CompactionInputFiles>& inputs,
+  bool EnoughRoomForCompaction(ColumnFamilyData* cfd,
+                               const std::vector<CompactionInputFiles>& inputs,
                               bool* sfm_bookkeeping, LogBuffer* log_buffer);

  void PrintStatistics();
@@ -1021,8 +1081,7 @@ class DBImpl : public DB {
  // helper functions for adding and removing from flush & compaction queues
  void AddToCompactionQueue(ColumnFamilyData* cfd);
  ColumnFamilyData* PopFirstFromCompactionQueue();
-  void AddToFlushQueue(ColumnFamilyData* cfd, FlushReason flush_reason);
-  ColumnFamilyData* PopFirstFromFlushQueue();
+  FlushRequest PopFirstFromFlushQueue();

  // helper function to call after some of the logs_ were synced
  void MarkLogsSynced(uint64_t up_to, bool synced_dir, const Status& status);
@@ -1035,6 +1094,10 @@ class DBImpl : public DB {

  Status CloseHelper();

+  Status FlushAllCFs(FlushReason flush_reason);
+
+  void WaitForBackgroundWork();
+
  // table_cache_ provides its own synchronization
  std::shared_ptr<Cache> table_cache_;

@@ -1255,7 +1318,7 @@ class DBImpl : public DB {
  // in MaybeScheduleFlushOrCompaction()
  // invariant(column family present in flush_queue_ <==>
  // ColumnFamilyData::pending_flush_ == true)
-  std::deque<ColumnFamilyData*> flush_queue_;
+  std::deque<FlushRequest> flush_queue_;
  // invariant(column family present in compaction_queue_ <==>
  // ColumnFamilyData::pending_compaction_ == true)
  std::deque<ColumnFamilyData*> compaction_queue_;
@@ -1479,6 +1542,16 @@ class DBImpl : public DB {
  // flush/compaction and if it is not provided vis SnapshotChecker, we should
  // disable gc to be safe.
  const bool use_custom_gc_;
+  // Flag to indicate that the DB instance shutdown has been initiated. This
+  // different from shutting_down_ atomic in that it is set at the beginning
+  // of shutdown sequence, specifically in order to prevent any background
+  // error recovery from going on in parallel. The latter, shutting_down_,
+  // is set a little later during the shutdown after scheduling memtable
+  // flushes
+  bool shutdown_initiated_;
+  // Flag to indicate whether sst_file_manager object was allocated in
+  // DB::Open() or passed to us
+  bool own_sfm_;

  // Clients must periodically call SetPreserveDeletesSequenceNumber()
  // to advance this seqnum. Default value is 0 which means ALL deletes are
@@ -26,7 +26,7 @@
 namespace rocksdb {

 bool DBImpl::EnoughRoomForCompaction(
-    const std::vector<CompactionInputFiles>& inputs,
+    ColumnFamilyData* cfd, const std::vector<CompactionInputFiles>& inputs,
    bool* sfm_reserved_compact_space, LogBuffer* log_buffer) {
  // Check if we have enough room to do the compaction
  bool enough_room = true;
@@ -34,12 +34,17 @@ bool DBImpl::EnoughRoomForCompaction(
  auto sfm = static_cast<SstFileManagerImpl*>(
      immutable_db_options_.sst_file_manager.get());
  if (sfm) {
-    enough_room = sfm->EnoughRoomForCompaction(inputs);
+    // Pass the current bg_error_ to SFM so it can decide what checks to
+    // perform. If this DB instance hasn't seen any error yet, the SFM can be
+    // optimistic and not do disk space checks
+    enough_room =
+        sfm->EnoughRoomForCompaction(cfd, inputs, error_handler_.GetBGError());
    if (enough_room) {
      *sfm_reserved_compact_space = true;
    }
  }
 #else
+  (void)cfd;
  (void)inputs;
  (void)sfm_reserved_compact_space;
 #endif  // ROCKSDB_LITE
@@ -104,7 +109,8 @@ Status DBImpl::SyncClosedLogs(JobContext* job_context) {

 Status DBImpl::FlushMemTableToOutputFile(
    ColumnFamilyData* cfd, const MutableCFOptions& mutable_cf_options,
-    bool* made_progress, JobContext* job_context, LogBuffer* log_buffer) {
+    bool* made_progress, JobContext* job_context,
+    SuperVersionContext* superversion_context, LogBuffer* log_buffer) {
  mutex_.AssertHeld();
  assert(cfd->imm()->NumNotFlushed() != 0);
  assert(cfd->imm()->IsFlushPending());
@@ -160,8 +166,8 @@ Status DBImpl::FlushMemTableToOutputFile(
  }

  if (s.ok()) {
-    InstallSuperVersionAndScheduleWork(
-        cfd, &job_context->superversion_contexts[0], mutable_cf_options);
+    InstallSuperVersionAndScheduleWork(cfd, superversion_context,
+                                       mutable_cf_options);
    if (made_progress) {
      *made_progress = 1;
    }
@@ -200,6 +206,25 @@ Status DBImpl::FlushMemTableToOutputFile(
  return s;
 }

+Status DBImpl::FlushMemTablesToOutputFiles(
+    const autovector<BGFlushArg>& bg_flush_args, bool* made_progress,
+    JobContext* job_context, LogBuffer* log_buffer) {
+  Status s;
+  for (auto& arg : bg_flush_args) {
+    ColumnFamilyData* cfd = arg.cfd_;
+    const MutableCFOptions& mutable_cf_options =
+        *cfd->GetLatestMutableCFOptions();
+    SuperVersionContext* superversion_context = arg.superversion_context_;
+    s = FlushMemTableToOutputFile(cfd, mutable_cf_options, made_progress,
+                                  job_context, superversion_context,
+                                  log_buffer);
+    if (!s.ok()) {
+      break;
+    }
+  }
+  return s;
+}
+
 void DBImpl::NotifyOnFlushBegin(ColumnFamilyData* cfd, FileMetaData* file_meta,
                                const MutableCFOptions& mutable_cf_options,
                                int job_id, TableProperties prop) {
@@ -324,60 +349,12 @@ Status DBImpl::CompactRange(const CompactRangeOptions& options,
    CleanupSuperVersion(super_version);
  }

-  if (!options.allow_write_stall && flush_needed) {
-    InstrumentedMutexLock l(&mutex_);
-    uint64_t orig_active_memtable_id = cfd->mem()->GetID();
-    WriteStallCondition write_stall_condition = WriteStallCondition::kNormal;
-    do {
-      if (write_stall_condition != WriteStallCondition::kNormal) {
-        TEST_SYNC_POINT("DBImpl::CompactRange:StallWait");
-        ROCKS_LOG_INFO(immutable_db_options_.info_log,
-                       "[%s] CompactRange waiting on stall conditions to clear",
-                       cfd->GetName().c_str());
-        bg_cv_.Wait();
-      }
-      if (cfd->IsDropped() || shutting_down_.load(std::memory_order_acquire)) {
-        return Status::ShutdownInProgress();
-      }
-
-      uint64_t earliest_memtable_id =
-          std::min(cfd->mem()->GetID(), cfd->imm()->GetEarliestMemTableID());
-      if (earliest_memtable_id > orig_active_memtable_id) {
-        // We waited so long that the memtable we were originally waiting on was
-        // flushed.
-        flush_needed = false;
-        break;
-      }
-
-      const auto& mutable_cf_options = *cfd->GetLatestMutableCFOptions();
-      const auto* vstorage = cfd->current()->storage_info();
-
-      // Skip stalling check if we're below auto-flush and auto-compaction
-      // triggers. If it stalled in these conditions, that'd mean the stall
-      // triggers are so low that stalling is needed for any background work. In
-      // that case we shouldn't wait since background work won't be scheduled.
-      if (cfd->imm()->NumNotFlushed() <
-              cfd->ioptions()->min_write_buffer_number_to_merge &&
-          vstorage->l0_delay_trigger_count() <
-              mutable_cf_options.level0_file_num_compaction_trigger) {
-        break;
-      }
-
-      // check whether one extra immutable memtable or an extra L0 file would
-      // cause write stalling mode to be entered. It could still enter stall
-      // mode due to pending compaction bytes, but that's less common
-      write_stall_condition =
-          ColumnFamilyData::GetWriteStallConditionAndCause(
-              cfd->imm()->NumNotFlushed() + 1,
-              vstorage->l0_delay_trigger_count() + 1,
-              vstorage->estimated_compaction_needed_bytes(), mutable_cf_options)
-              .first;
-    } while (write_stall_condition != WriteStallCondition::kNormal);
-  }
-  TEST_SYNC_POINT("DBImpl::CompactRange:StallWaitDone");
  Status s;
  if (flush_needed) {
-    s = FlushMemTable(cfd, FlushOptions(), FlushReason::kManualCompaction);
+    FlushOptions fo;
+    fo.allow_write_stall = options.allow_write_stall;
+    s = FlushMemTable(cfd, fo, FlushReason::kManualCompaction,
+      false /* writes_stopped*/);
    if (!s.ok()) {
      LogFlush(immutable_db_options_.info_log);
      return s;
@@ -612,7 +589,7 @@ Status DBImpl::CompactFilesImpl(
  bool sfm_reserved_compact_space = false;
  // First check if we have enough room to do the compaction
  bool enough_room = EnoughRoomForCompaction(
-      input_files, &sfm_reserved_compact_space, log_buffer);
+      cfd, input_files, &sfm_reserved_compact_space, log_buffer);

  if (!enough_room) {
    // m's vars will get set properly at the end of this function,
@@ -942,6 +919,68 @@ Status DBImpl::Flush(const FlushOptions& flush_options,
  return s;
 }

+
+Status DBImpl::FlushAllCFs(FlushReason flush_reason) {
+  Status s;
+  WriteContext context;
+  WriteThread::Writer w;
+
+  mutex_.AssertHeld();
+  write_thread_.EnterUnbatched(&w, &mutex_);
+
+  FlushRequest flush_req;
+  for (auto cfd : *versions_->GetColumnFamilySet()) {
+    if (cfd->imm()->NumNotFlushed() == 0 && cfd->mem()->IsEmpty() &&
+        cached_recoverable_state_empty_.load()) {
+      // Nothing to flush
+      continue;
+    }
+
+    // SwitchMemtable() will release and reacquire mutex during execution
+    s = SwitchMemtable(cfd, &context);
+    if (!s.ok()) {
+      break;
+    }
+
+    cfd->imm()->FlushRequested();
+
+    flush_req.emplace_back(cfd, cfd->imm()->GetLatestMemTableID());
+  }
+
+  // schedule flush
+  if (s.ok() && !flush_req.empty()) {
+    SchedulePendingFlush(flush_req, flush_reason);
+    MaybeScheduleFlushOrCompaction();
+  }
+
+  write_thread_.ExitUnbatched(&w);
+
+  if (s.ok()) {
+    for (auto& flush : flush_req) {
+      auto cfd = flush.first;
+      auto flush_memtable_id = flush.second;
+      while (cfd->imm()->NumNotFlushed() > 0 &&
+             cfd->imm()->GetEarliestMemTableID() <= flush_memtable_id) {
+        if (!error_handler_.GetRecoveryError().ok()) {
+          break;
+        }
+        if (cfd->IsDropped()) {
+          // FlushJob cannot flush a dropped CF, if we did not break here
+          // we will loop forever since cfd->imm()->NumNotFlushed() will never
+          // drop to zero
+          continue;
+        }
+        cfd->Ref();
+        bg_cv_.Wait();
+        cfd->Unref();
+      }
+    }
+  }
+
+  flush_req.clear();
+  return s;
+}
+
 Status DBImpl::RunManualCompaction(ColumnFamilyData* cfd, int input_level,
                                   int output_level, uint32_t output_path_id,
                                   uint32_t max_subcompactions,
@@ -1077,63 +1116,164 @@ Status DBImpl::FlushMemTable(ColumnFamilyData* cfd,
                             FlushReason flush_reason, bool writes_stopped) {
  Status s;
  uint64_t flush_memtable_id = 0;
+  if (!flush_options.allow_write_stall) {
+    bool flush_needed = true;
+    s = WaitUntilFlushWouldNotStallWrites(cfd, &flush_needed);
+    TEST_SYNC_POINT("DBImpl::FlushMemTable:StallWaitDone");
+    if (!s.ok() || !flush_needed) {
+      return s;
+    }
+  }
+  FlushRequest flush_req;
  {
    WriteContext context;
    InstrumentedMutexLock guard_lock(&mutex_);

-    if (cfd->imm()->NumNotFlushed() == 0 && cfd->mem()->IsEmpty() &&
-        cached_recoverable_state_empty_.load()) {
-      // Nothing to flush
-      return Status::OK();
-    }
-
    WriteThread::Writer w;
    if (!writes_stopped) {
      write_thread_.EnterUnbatched(&w, &mutex_);
    }

-    // SwitchMemtable() will release and reacquire mutex during execution
-    s = SwitchMemtable(cfd, &context);
-    flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+    if (cfd->imm()->NumNotFlushed() != 0 || !cfd->mem()->IsEmpty() ||
+        !cached_recoverable_state_empty_.load()) {
+      s = SwitchMemtable(cfd, &context);
+      flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+      flush_req.emplace_back(cfd, flush_memtable_id);
+    }
+
+    if (s.ok() && !flush_req.empty()) {
+      for (auto& elem : flush_req) {
+        ColumnFamilyData* loop_cfd = elem.first;
+        loop_cfd->imm()->FlushRequested();
+      }
+      SchedulePendingFlush(flush_req, flush_reason);
+      MaybeScheduleFlushOrCompaction();
+    }

    if (!writes_stopped) {
      write_thread_.ExitUnbatched(&w);
    }
-
-    cfd->imm()->FlushRequested();
-
-    // schedule flush
-    SchedulePendingFlush(cfd, flush_reason);
-    MaybeScheduleFlushOrCompaction();
  }

  if (s.ok() && flush_options.wait) {
-    // Wait until the compaction completes
-    s = WaitForFlushMemTable(cfd, &flush_memtable_id);
+    autovector<ColumnFamilyData*> cfds;
+    autovector<const uint64_t*> flush_memtable_ids;
+    for (auto& iter : flush_req) {
+      cfds.push_back(iter.first);
+      flush_memtable_ids.push_back(&(iter.second));
+    }
+    s = WaitForFlushMemTables(cfds, flush_memtable_ids);
  }
  TEST_SYNC_POINT("FlushMemTableFinished");
  return s;
 }

-Status DBImpl::WaitForFlushMemTable(ColumnFamilyData* cfd,
-                                    const uint64_t* flush_memtable_id) {
-  Status s;
+// Calling FlushMemTable(), whether from DB::Flush() or from Backup Engine, can
+// cause write stall, for example if one memtable is being flushed already.
+// This method tries to avoid write stall (similar to CompactRange() behavior)
+// it emulates how the SuperVersion / LSM would change if flush happens, checks
+// it against various constrains and delays flush if it'd cause write stall.
+// Called should check status and flush_needed to see if flush already happened.
+Status DBImpl::WaitUntilFlushWouldNotStallWrites(ColumnFamilyData* cfd,
+    bool* flush_needed) {
+  {
+    *flush_needed = true;
+    InstrumentedMutexLock l(&mutex_);
+    uint64_t orig_active_memtable_id = cfd->mem()->GetID();
+    WriteStallCondition write_stall_condition = WriteStallCondition::kNormal;
+    do {
+      if (write_stall_condition != WriteStallCondition::kNormal) {
+        TEST_SYNC_POINT("DBImpl::WaitUntilFlushWouldNotStallWrites:StallWait");
+        ROCKS_LOG_INFO(immutable_db_options_.info_log,
+                       "[%s] WaitUntilFlushWouldNotStallWrites"
+                       " waiting on stall conditions to clear",
+                       cfd->GetName().c_str());
+        bg_cv_.Wait();
+      }
+      if (cfd->IsDropped() || shutting_down_.load(std::memory_order_acquire)) {
+        return Status::ShutdownInProgress();
+      }
+
+      uint64_t earliest_memtable_id =
+          std::min(cfd->mem()->GetID(), cfd->imm()->GetEarliestMemTableID());
+      if (earliest_memtable_id > orig_active_memtable_id) {
+        // We waited so long that the memtable we were originally waiting on was
+        // flushed.
+        *flush_needed = false;
+        return Status::OK();
+      }
+
+      const auto& mutable_cf_options = *cfd->GetLatestMutableCFOptions();
+      const auto* vstorage = cfd->current()->storage_info();
+
+      // Skip stalling check if we're below auto-flush and auto-compaction
+      // triggers. If it stalled in these conditions, that'd mean the stall
+      // triggers are so low that stalling is needed for any background work. In
+      // that case we shouldn't wait since background work won't be scheduled.
+      if (cfd->imm()->NumNotFlushed() <
+              cfd->ioptions()->min_write_buffer_number_to_merge &&
+          vstorage->l0_delay_trigger_count() <
+              mutable_cf_options.level0_file_num_compaction_trigger) {
+        break;
+      }
+
+      // check whether one extra immutable memtable or an extra L0 file would
+      // cause write stalling mode to be entered. It could still enter stall
+      // mode due to pending compaction bytes, but that's less common
+      write_stall_condition =
+          ColumnFamilyData::GetWriteStallConditionAndCause(
+              cfd->imm()->NumNotFlushed() + 1,
+              vstorage->l0_delay_trigger_count() + 1,
+              vstorage->estimated_compaction_needed_bytes(), mutable_cf_options)
+              .first;
+    } while (write_stall_condition != WriteStallCondition::kNormal);
+  }
+  return Status::OK();
+}
+
+// Wait for memtables to be flushed for multiple column families.
+// let N = cfds.size()
+// for i in [0, N),
+//  1) if flush_memtable_ids[i] is not null, then the memtables with lower IDs
+//     have to be flushed for THIS column family;
+//  2) if flush_memtable_ids[i] is null, then all memtables in THIS column
+//     family have to be flushed.
+// Finish waiting when ALL column families finish flushing memtables.
+Status DBImpl::WaitForFlushMemTables(
+    const autovector<ColumnFamilyData*>& cfds,
+    const autovector<const uint64_t*>& flush_memtable_ids) {
+  int num = static_cast<int>(cfds.size());
  // Wait until the compaction completes
  InstrumentedMutexLock l(&mutex_);
-  while (cfd->imm()->NumNotFlushed() > 0 && !error_handler_.IsDBStopped() &&
-         (flush_memtable_id == nullptr ||
-          cfd->imm()->GetEarliestMemTableID() <= *flush_memtable_id)) {
+  while (!error_handler_.IsDBStopped()) {
    if (shutting_down_.load(std::memory_order_acquire)) {
      return Status::ShutdownInProgress();
    }
-    if (cfd->IsDropped()) {
-      // FlushJob cannot flush a dropped CF, if we did not break here
-      // we will loop forever since cfd->imm()->NumNotFlushed() will never
-      // drop to zero
+    // Number of column families that have been dropped.
+    int num_dropped = 0;
+    // Number of column families that have finished flush.
+    int num_finished = 0;
+    for (int i = 0; i < num; ++i) {
+      if (cfds[i]->IsDropped()) {
+        ++num_dropped;
+      } else if (cfds[i]->imm()->NumNotFlushed() == 0 ||
+                 (flush_memtable_ids[i] != nullptr &&
+                  cfds[i]->imm()->GetEarliestMemTableID() >
+                      *flush_memtable_ids[i])) {
+        ++num_finished;
+      }
+    }
+    if (1 == num_dropped && 1 == num) {
      return Status::InvalidArgument("Cannot flush a dropped CF");
    }
+    // Column families involved in this flush request have either been dropped
+    // or finished flush. Then it's time to finish waiting.
+    if (num_dropped + num_finished == num) {
+      break;
+    }
    bg_cv_.Wait();
  }
+  Status s;
  if (error_handler_.IsDBStopped()) {
    s = error_handler_.GetBGError();
  }
@@ -1163,6 +1303,12 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
  if (bg_work_paused_ > 0) {
    // we paused the background work
    return;
+  } else if (error_handler_.IsBGWorkStopped() &&
+      !error_handler_.IsRecoveryInProgress()) {
+    // There has been a hard error and this call is not part of the recovery
+    // sequence. Bail out here so we don't get into an endless loop of
+    // scheduling BG work which will again call this function
+    return;
  } else if (shutting_down_.load(std::memory_order_acquire)) {
    // DB is being deleted; no more background compactions
    return;
@@ -1172,7 +1318,6 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
      env_->GetBackgroundThreads(Env::Priority::HIGH) == 0;
  while (!is_flush_pool_empty && unscheduled_flushes_ > 0 &&
         bg_flush_scheduled_ < bg_job_limits.max_flushes) {
-    unscheduled_flushes_--;
    bg_flush_scheduled_++;
    env_->Schedule(&DBImpl::BGWorkFlush, this, Env::Priority::HIGH, this);
  }
@@ -1183,7 +1328,6 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
    while (unscheduled_flushes_ > 0 &&
           bg_flush_scheduled_ + bg_compaction_scheduled_ <
               bg_job_limits.max_flushes) {
-      unscheduled_flushes_--;
      bg_flush_scheduled_++;
      env_->Schedule(&DBImpl::BGWorkFlush, this, Env::Priority::LOW, this);
    }
@@ -1192,6 +1336,12 @@ void DBImpl::MaybeScheduleFlushOrCompaction() {
  if (bg_compaction_paused_ > 0) {
    // we paused the background compaction
    return;
+  } else if (error_handler_.IsBGWorkStopped()) {
+    // Compaction is not part of the recovery sequence from a hard error. We
+    // might get here because recovery might do a flush and install a new
+    // super version, which will try to schedule pending compactions. Bail
+    // out here and let the higher level recovery handle compactions
+    return;
  }

  if (HasExclusiveManualCompaction()) {
@@ -1260,30 +1410,28 @@ ColumnFamilyData* DBImpl::PopFirstFromCompactionQueue() {
  return cfd;
 }

-void DBImpl::AddToFlushQueue(ColumnFamilyData* cfd, FlushReason flush_reason) {
-  assert(!cfd->queued_for_flush());
-  cfd->Ref();
-  flush_queue_.push_back(cfd);
-  cfd->set_queued_for_flush(true);
-  cfd->SetFlushReason(flush_reason);
-}
-
-ColumnFamilyData* DBImpl::PopFirstFromFlushQueue() {
+DBImpl::FlushRequest DBImpl::PopFirstFromFlushQueue() {
  assert(!flush_queue_.empty());
-  auto cfd = *flush_queue_.begin();
+  FlushRequest flush_req = flush_queue_.front();
+  assert(unscheduled_flushes_ >= static_cast<int>(flush_req.size()));
+  unscheduled_flushes_ -= static_cast<int>(flush_req.size());
  flush_queue_.pop_front();
-  assert(cfd->queued_for_flush());
-  cfd->set_queued_for_flush(false);
  // TODO: need to unset flush reason?
-  return cfd;
+  return flush_req;
 }

-void DBImpl::SchedulePendingFlush(ColumnFamilyData* cfd,
+void DBImpl::SchedulePendingFlush(const FlushRequest& flush_req,
                                  FlushReason flush_reason) {
-  if (!cfd->queued_for_flush() && cfd->imm()->IsFlushPending()) {
-    AddToFlushQueue(cfd, flush_reason);
-    ++unscheduled_flushes_;
+  if (flush_req.empty()) {
+    return;
  }
+  for (auto& iter : flush_req) {
+    ColumnFamilyData* cfd = iter.first;
+    cfd->Ref();
+    cfd->SetFlushReason(flush_reason);
+  }
+  unscheduled_flushes_ += static_cast<int>(flush_req.size());
+  flush_queue_.push_back(flush_req);
 }

 void DBImpl::SchedulePendingCompaction(ColumnFamilyData* cfd) {
@@ -1351,15 +1499,18 @@ void DBImpl::UnscheduleCallback(void* arg) {
 }

 Status DBImpl::BackgroundFlush(bool* made_progress, JobContext* job_context,
-                               LogBuffer* log_buffer) {
+                               LogBuffer* log_buffer, FlushReason* reason) {
  mutex_.AssertHeld();

  Status status;
+  *reason = FlushReason::kOthers;
+  // If BG work is stopped due to an error, but a recovery is in progress,
+  // that means this flush is part of the recovery. So allow it to go through
  if (!error_handler_.IsBGWorkStopped()) {
    if (shutting_down_.load(std::memory_order_acquire)) {
      status = Status::ShutdownInProgress();
    }
-  } else {
+  } else if (!error_handler_.IsRecoveryInProgress()) {
    status = error_handler_.GetBGError();
  }

@@ -1367,40 +1518,58 @@ Status DBImpl::BackgroundFlush(bool* made_progress, JobContext* job_context,
    return status;
  }

-  ColumnFamilyData* cfd = nullptr;
+  autovector<BGFlushArg> bg_flush_args;
+  std::vector<SuperVersionContext>& superversion_contexts =
+      job_context->superversion_contexts;
  while (!flush_queue_.empty()) {
    // This cfd is already referenced
-    auto first_cfd = PopFirstFromFlushQueue();
+    const FlushRequest& flush_req = PopFirstFromFlushQueue();
+    superversion_contexts.clear();
+    superversion_contexts.reserve(flush_req.size());

-    if (first_cfd->IsDropped() || !first_cfd->imm()->IsFlushPending()) {
-      // can't flush this CF, try next one
-      if (first_cfd->Unref()) {
-        delete first_cfd;
+    for (const auto& iter : flush_req) {
+      ColumnFamilyData* cfd = iter.first;
+      if (cfd->IsDropped() || !cfd->imm()->IsFlushPending()) {
+        // can't flush this CF, try next one
+        if (cfd->Unref()) {
+          delete cfd;
+        }
+        continue;
      }
-      continue;
+      superversion_contexts.emplace_back(SuperVersionContext(true));
+      bg_flush_args.emplace_back(cfd, iter.second,
+                                 &(superversion_contexts.back()));
+    }
+    if (!bg_flush_args.empty()) {
+      break;
    }
-
-    // found a flush!
-    cfd = first_cfd;
-    break;
  }

-  if (cfd != nullptr) {
-    const MutableCFOptions mutable_cf_options =
-        *cfd->GetLatestMutableCFOptions();
+  if (!bg_flush_args.empty()) {
    auto bg_job_limits = GetBGJobLimits();
-    ROCKS_LOG_BUFFER(
-        log_buffer,
-        "Calling FlushMemTableToOutputFile with column "
-        "family [%s], flush slots available %d, compaction slots available %d, "
-        "flush slots scheduled %d, compaction slots scheduled %d",
-        cfd->GetName().c_str(), bg_job_limits.max_flushes,
-        bg_job_limits.max_compactions, bg_flush_scheduled_,
-        bg_compaction_scheduled_);
-    status = FlushMemTableToOutputFile(cfd, mutable_cf_options, made_progress,
-                                       job_context, log_buffer);
-    if (cfd->Unref()) {
-      delete cfd;
+    for (const auto& arg : bg_flush_args) {
+      ColumnFamilyData* cfd = arg.cfd_;
+      ROCKS_LOG_BUFFER(
+          log_buffer,
+          "Calling FlushMemTableToOutputFile with column "
+          "family [%s], flush slots available %d, compaction slots available "
+          "%d, "
+          "flush slots scheduled %d, compaction slots scheduled %d",
+          cfd->GetName().c_str(), bg_job_limits.max_flushes,
+          bg_job_limits.max_compactions, bg_flush_scheduled_,
+          bg_compaction_scheduled_);
+    }
+    status = FlushMemTablesToOutputFiles(bg_flush_args, made_progress,
+                                         job_context, log_buffer);
+    // All the CFDs in the FlushReq must have the same flush reason, so just
+    // grab the first one
+    *reason = bg_flush_args[0].cfd_->GetFlushReason();
+    for (auto& arg : bg_flush_args) {
+      ColumnFamilyData* cfd = arg.cfd_;
+      if (cfd->Unref()) {
+        delete cfd;
+        arg.cfd_ = nullptr;
+      }
    }
  }
  return status;
@@ -1421,9 +1590,12 @@ void DBImpl::BackgroundCallFlush() {

    auto pending_outputs_inserted_elem =
        CaptureCurrentFileNumberInPendingOutputs();
+    FlushReason reason;

-    Status s = BackgroundFlush(&made_progress, &job_context, &log_buffer);
-    if (!s.ok() && !s.IsShutdownInProgress()) {
+    Status s =
+        BackgroundFlush(&made_progress, &job_context, &log_buffer, &reason);
+    if (!s.ok() && !s.IsShutdownInProgress() &&
+        reason != FlushReason::kErrorRecovery) {
      // Wait a little bit before retrying background flush in
      // case this is an environmental problem and we do not want to
      // chew up resources for failed flushes for the duration of
@@ -1613,6 +1785,11 @@ Status DBImpl::BackgroundCompaction(bool* made_progress,
    }
  } else {
    status = error_handler_.GetBGError();
+    // If we get here, it means a hard error happened after this compaction
+    // was scheduled by MaybeScheduleFlushOrCompaction(), but before it got
+    // a chance to execute. Since we didn't pop a cfd from the compaction
+    // queue, increment unscheduled_compactions_
+    unscheduled_compactions_++;
  }

  if (!status.ok()) {
@@ -1648,7 +1825,7 @@ Status DBImpl::BackgroundCompaction(bool* made_progress,
    } else {
      // First check if we have enough room to do the compaction
      bool enough_room = EnoughRoomForCompaction(
-          *(c->inputs()), &sfm_reserved_compact_space, log_buffer);
+          m->cfd, *(c->inputs()), &sfm_reserved_compact_space, log_buffer);

      if (!enough_room) {
        // Then don't do the compaction
@@ -1711,7 +1888,7 @@ Status DBImpl::BackgroundCompaction(bool* made_progress,

      if (c != nullptr) {
        bool enough_room = EnoughRoomForCompaction(
-            *(c->inputs()), &sfm_reserved_compact_space, log_buffer);
+            cfd, *(c->inputs()), &sfm_reserved_compact_space, log_buffer);

        if (!enough_room) {
          // Then don't do the compaction
@@ -1920,8 +2097,6 @@ Status DBImpl::BackgroundCompaction(bool* made_progress,
    NotifyOnCompactionCompleted(c->column_family_data(), c.get(), status,
                                compaction_job_stats, job_context->job_id);
  }
-  // this will unref its input_version and column_family_data
-  c.reset();

  if (status.ok() || status.IsCompactionTooLarge()) {
    // Done
@@ -1931,7 +2106,26 @@ Status DBImpl::BackgroundCompaction(bool* made_progress,
    ROCKS_LOG_WARN(immutable_db_options_.info_log, "Compaction error: %s",
                   status.ToString().c_str());
    error_handler_.SetBGError(status, BackgroundErrorReason::kCompaction);
+    if (c != nullptr && !is_manual && !error_handler_.IsBGWorkStopped()) {
+      // Put this cfd back in the compaction queue so we can retry after some
+      // time
+      auto cfd = c->column_family_data();
+      assert(cfd != nullptr);
+      // Since this compaction failed, we need to recompute the score so it
+      // takes the original input files into account
+      c->column_family_data()
+          ->current()
+          ->storage_info()
+          ->ComputeCompactionScore(*(c->immutable_cf_options()),
+                                   *(c->mutable_cf_options()));
+      if (!cfd->queued_for_compaction()) {
+        AddToCompactionQueue(cfd);
+        ++unscheduled_compactions_;
+      }
+    }
  }
+  // this will unref its input_version and column_family_data
+  c.reset();

  if (is_manual) {
    ManualCompactionState* m = manual_compaction;
@@ -2080,7 +2274,10 @@ bool DBImpl::MCOverlap(ManualCompactionState* m, ManualCompactionState* m1) {

 void DBImpl::InstallSuperVersionAndScheduleWork(
    ColumnFamilyData* cfd, SuperVersionContext* sv_context,
-    const MutableCFOptions& mutable_cf_options, FlushReason flush_reason) {
+    const MutableCFOptions& mutable_cf_options,
+    FlushReason /* flush_reason */) {
+  // TODO(yanqin) investigate if 'flush_reason' can be removed since it's not
+  // used.
  mutex_.AssertHeld();

  // Update max_total_in_memory_state_
@@ -2099,7 +2296,6 @@ void DBImpl::InstallSuperVersionAndScheduleWork(

  // Whenever we install new SuperVersion, we might need to issue new flushes or
  // compactions.
-  SchedulePendingFlush(cfd, flush_reason);
  SchedulePendingCompaction(cfd);
  MaybeScheduleFlushOrCompaction();

@@ -100,9 +100,11 @@ Status DBImpl::TEST_SwitchMemtable(ColumnFamilyData* cfd) {
  return SwitchMemtable(cfd, &write_context);
 }

-Status DBImpl::TEST_FlushMemTable(bool wait, ColumnFamilyHandle* cfh) {
+Status DBImpl::TEST_FlushMemTable(bool wait, bool allow_write_stall,
+    ColumnFamilyHandle* cfh) {
  FlushOptions fo;
  fo.wait = wait;
+  fo.allow_write_stall = allow_write_stall;
  ColumnFamilyData* cfd;
  if (cfh == nullptr) {
    cfd = default_cf_handle_->cfd();
@@ -135,7 +137,7 @@ Status DBImpl::TEST_WaitForCompact(bool wait_unscheduled) {
  while ((bg_bottom_compaction_scheduled_ || bg_compaction_scheduled_ ||
          bg_flush_scheduled_ ||
          (wait_unscheduled && unscheduled_compactions_)) &&
-         !error_handler_.IsDBStopped()) {
+         (error_handler_.GetBGError() == Status::OK())) {
    bg_cv_.Wait();
  }
  return error_handler_.GetBGError();
@@ -235,5 +237,11 @@ SequenceNumber DBImpl::TEST_GetLastVisibleSequence() const {
  }
 }

+size_t DBImpl::TEST_GetWalPreallocateBlockSize(
+    uint64_t write_buffer_size) const {
+  InstrumentedMutexLock l(&mutex_);
+  return GetWalPreallocateBlockSize(write_buffer_size);
+}
+
 }  // namespace rocksdb
 #endif  // NDEBUG
@@ -134,8 +134,15 @@ DBOptions SanitizeOptions(const std::string& dbname, const DBOptions& src) {
  for (size_t i = 0; i < result.db_paths.size(); i++) {
    DeleteScheduler::CleanupDirectory(result.env, sfm, result.db_paths[i].path);
  }
-#endif

+  // Create a default SstFileManager for purposes of tracking compaction size
+  // and facilitating recovery from out of space errors.
+  if (result.sst_file_manager.get() == nullptr) {
+    std::shared_ptr<SstFileManager> sst_file_manager(
+        NewSstFileManager(result.env, result.info_log));
+    result.sst_file_manager = sst_file_manager;
+  }
+#endif
  return result;
 }

@@ -232,7 +239,7 @@ Status DBImpl::NewDB() {
    file->SetPreallocationBlockSize(
        immutable_db_options_.manifest_preallocation_size);
    unique_ptr<WritableFileWriter> file_writer(
-        new WritableFileWriter(std::move(file), env_options));
+        new WritableFileWriter(std::move(file), manifest, env_options));
    log::Writer log(std::move(file_writer), 0, false);
    std::string record;
    new_db.EncodeTo(&record);
@@ -389,6 +396,16 @@ Status DBImpl::Recover(
      }
    }
  }
+
+  // Initial max_total_in_memory_state_ before recovery logs. Log recovery
+  // may check this value to decide whether to flush.
+  max_total_in_memory_state_ = 0;
+  for (auto cfd : *versions_->GetColumnFamilySet()) {
+    auto* mutable_cf_options = cfd->GetLatestMutableCFOptions();
+    max_total_in_memory_state_ += mutable_cf_options->write_buffer_size *
+                                  mutable_cf_options->max_write_buffer_number;
+  }
+
  if (s.ok()) {
    SequenceNumber next_sequence(kMaxSequenceNumber);
    default_cf_handle_ = new ColumnFamilyHandleImpl(
@@ -461,14 +478,6 @@ Status DBImpl::Recover(
    }
  }

-  // Initial value
-  max_total_in_memory_state_ = 0;
-  for (auto cfd : *versions_->GetColumnFamilySet()) {
-    auto* mutable_cf_options = cfd->GetLatestMutableCFOptions();
-    max_total_in_memory_state_ += mutable_cf_options->write_buffer_size *
-                                  mutable_cf_options->max_write_buffer_number;
-  }
-
  return s;
 }

@@ -598,8 +607,7 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
    // to be skipped instead of propagating bad information (like overly
    // large sequence numbers).
    log::Reader reader(immutable_db_options_.info_log, std::move(file_reader),
-                       &reporter, true /*checksum*/, 0 /*initial_offset*/,
-                       log_number);
+                       &reporter, true /*checksum*/, log_number);

    // Determine if we should tolerate incomplete records at the tail end of the
    // Read all the records and add to a memtable
@@ -879,18 +887,8 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
    }
  }

-  if (data_seen && !flushed) {
-    // Mark these as alive so they'll be considered for deletion later by
-    // FindObsoleteFiles()
-    if (two_write_queues_) {
-      log_write_mutex_.Lock();
-    }
-    for (auto log_number : log_numbers) {
-      alive_log_files_.push_back(LogFileNumberSize(log_number));
-    }
-    if (two_write_queues_) {
-      log_write_mutex_.Unlock();
-    }
+  if (status.ok() && data_seen && !flushed) {
+    status = RestoreAliveLogFiles(log_numbers);
  }

  event_logger_.Log() << "job" << job_id << "event"
@@ -899,6 +897,60 @@ Status DBImpl::RecoverLogFiles(const std::vector<uint64_t>& log_numbers,
  return status;
 }

+Status DBImpl::RestoreAliveLogFiles(const std::vector<uint64_t>& log_numbers) {
+  if (log_numbers.empty()) {
+    return Status::OK();
+  }
+  Status s;
+  mutex_.AssertHeld();
+  assert(immutable_db_options_.avoid_flush_during_recovery);
+  if (two_write_queues_) {
+    log_write_mutex_.Lock();
+  }
+  // Mark these as alive so they'll be considered for deletion later by
+  // FindObsoleteFiles()
+  total_log_size_ = 0;
+  log_empty_ = false;
+  for (auto log_number : log_numbers) {
+    LogFileNumberSize log(log_number);
+    std::string fname = LogFileName(immutable_db_options_.wal_dir, log_number);
+    // This gets the appear size of the logs, not including preallocated space.
+    s = env_->GetFileSize(fname, &log.size);
+    if (!s.ok()) {
+      break;
+    }
+    total_log_size_ += log.size;
+    alive_log_files_.push_back(log);
+    // We preallocate space for logs, but then after a crash and restart, those
+    // preallocated space are not needed anymore. It is likely only the last
+    // log has such preallocated space, so we only truncate for the last log.
+    if (log_number == log_numbers.back()) {
+      std::unique_ptr<WritableFile> last_log;
+      Status truncate_status = env_->ReopenWritableFile(
+          fname, &last_log,
+          env_->OptimizeForLogWrite(
+              env_options_,
+              BuildDBOptions(immutable_db_options_, mutable_db_options_)));
+      if (truncate_status.ok()) {
+        truncate_status = last_log->Truncate(log.size);
+      }
+      if (truncate_status.ok()) {
+        truncate_status = last_log->Close();
+      }
+      // Not a critical error if fail to truncate.
+      if (!truncate_status.ok()) {
+        ROCKS_LOG_WARN(immutable_db_options_.info_log,
+                       "Failed to truncate log #%" PRIu64 ": %s", log_number,
+                       truncate_status.ToString().c_str());
+      }
+    }
+  }
+  if (two_write_queues_) {
+    log_write_mutex_.Unlock();
+  }
+  return s;
+}
+
 Status DBImpl::WriteLevel0TableForRecovery(int job_id, ColumnFamilyData* cfd,
                                           MemTable* mem, VersionEdit* edit) {
  mutex_.AssertHeld();
@@ -1051,6 +1103,12 @@ Status DBImpl::Open(const DBOptions& db_options, const std::string& dbname,
        break;
      }
    }
+
+    // For recovery from NoSpace() error, we can only handle
+    // the case where the database is stored in a single path
+    if (paths.size() <= 1) {
+      impl->error_handler_.EnableAutoRecovery();
+    }
  }

  if (!s.ok()) {
@@ -1075,10 +1133,10 @@ Status DBImpl::Open(const DBOptions& db_options, const std::string& dbname,
        impl->immutable_db_options_.env->OptimizeForLogWrite(
            soptions, BuildDBOptions(impl->immutable_db_options_,
                                     impl->mutable_db_options_));
-    s = NewWritableFile(
-        impl->immutable_db_options_.env,
-        LogFileName(impl->immutable_db_options_.wal_dir, new_log_number),
-        &lfile, opt_env_options);
+    std::string log_fname =
+        LogFileName(impl->immutable_db_options_.wal_dir, new_log_number);
+    s = NewWritableFile(impl->immutable_db_options_.env, log_fname, &lfile,
+                        opt_env_options);
    if (s.ok()) {
      lfile->SetWriteLifeTimeHint(write_hint);
      lfile->SetPreallocationBlockSize(
@@ -1086,8 +1144,8 @@ Status DBImpl::Open(const DBOptions& db_options, const std::string& dbname,
      {
        InstrumentedMutexLock wl(&impl->log_write_mutex_);
        impl->logfile_number_ = new_log_number;
-        unique_ptr<WritableFileWriter> file_writer(
-            new WritableFileWriter(std::move(lfile), opt_env_options));
+        unique_ptr<WritableFileWriter> file_writer(new WritableFileWriter(
+            std::move(lfile), log_fname, opt_env_options));
        impl->logs_.emplace_back(
            new_log_number,
            new log::Writer(
@@ -1214,6 +1272,14 @@ Status DBImpl::Open(const DBOptions& db_options, const std::string& dbname,
        }
      }
    }
+
+    // Reserve some disk buffer space. This is a heuristic - when we run out
+    // of disk space, this ensures that there is atleast write_buffer_size
+    // amount of free space before we resume DB writes. In low disk space
+    // conditions, we want to avoid a lot of small L0 files due to frequent
+    // WAL write failures and resultant forced flushes
+    sfm->ReserveDiskBuffer(max_write_buffer_size,
+                           impl->immutable_db_options_.db_paths[0].path);
  }
 #endif  // !ROCKSDB_LITE

@@ -31,6 +31,8 @@ Status DBImplReadOnly::Get(const ReadOptions& read_options,
                           ColumnFamilyHandle* column_family, const Slice& key,
                           PinnableSlice* pinnable_val) {
  assert(pinnable_val != nullptr);
+  // TODO: stopwatch DB_GET needed?, perf timer needed?
+  PERF_TIMER_GUARD(get_snapshot_time);
  Status s;
  SequenceNumber snapshot = versions_->LastSequence();
  auto cfh = reinterpret_cast<ColumnFamilyHandleImpl*>(column_family);
@@ -45,14 +47,22 @@ Status DBImplReadOnly::Get(const ReadOptions& read_options,
  MergeContext merge_context;
  RangeDelAggregator range_del_agg(cfd->internal_comparator(), snapshot);
  LookupKey lkey(key, snapshot);
+  PERF_TIMER_STOP(get_snapshot_time);
  if (super_version->mem->Get(lkey, pinnable_val->GetSelf(), &s, &merge_context,
                              &range_del_agg, read_options)) {
    pinnable_val->PinSelf();
+    RecordTick(stats_, MEMTABLE_HIT);
  } else {
    PERF_TIMER_GUARD(get_from_output_files_time);
    super_version->current->Get(read_options, lkey, pinnable_val, &s,
                                &merge_context, &range_del_agg);
+    RecordTick(stats_, MEMTABLE_MISS);
  }
+  RecordTick(stats_, NUMBER_KEYS_READ);
+  size_t size = pinnable_val->size();
+  RecordTick(stats_, BYTES_READ, size);
+  MeasureTime(stats_, BYTES_PER_READ, size);
+  PERF_COUNTER_ADD(get_read_bytes, size);
  return s;
 }

@@ -710,6 +710,10 @@ Status DBImpl::PreprocessWrite(const WriteOptions& write_options,
  assert(write_context != nullptr && need_log_sync != nullptr);
  Status status;

+  if (error_handler_.IsDBStopped()) {
+    status = error_handler_.GetBGError();
+  }
+
  PERF_TIMER_GUARD(write_scheduling_flushes_compactions_time);

  assert(!single_column_family_mode_ ||
@@ -728,10 +732,6 @@ Status DBImpl::PreprocessWrite(const WriteOptions& write_options,
    status = HandleWriteBufferFull(write_context);
  }

-  if (UNLIKELY(status.ok())) {
-    status = error_handler_.GetBGError();
-  }
-
  if (UNLIKELY(status.ok() && !flush_scheduler_.Empty())) {
    status = ScheduleFlushes(write_context);
  }
@@ -1064,6 +1064,7 @@ Status DBImpl::SwitchWAL(WriteContext* write_context) {
                 oldest_alive_log, total_log_size_.load(), GetMaxTotalWalSize());
  // no need to refcount because drop is happening in write thread, so can't
  // happen while we're in the write thread
+  FlushRequest flush_req;
  for (auto cfd : *versions_->GetColumnFamilySet()) {
    if (cfd->IsDropped()) {
      continue;
@@ -1073,11 +1074,14 @@ Status DBImpl::SwitchWAL(WriteContext* write_context) {
      if (!status.ok()) {
        break;
      }
+      flush_req.emplace_back(cfd, cfd->imm()->GetLatestMemTableID());
      cfd->imm()->FlushRequested();
-      SchedulePendingFlush(cfd, FlushReason::kWriteBufferManager);
    }
  }
-  MaybeScheduleFlushOrCompaction();
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferManager);
+    MaybeScheduleFlushOrCompaction();
+  }
  return status;
 }

@@ -1116,14 +1120,26 @@ Status DBImpl::HandleWriteBufferFull(WriteContext* write_context) {
      }
    }
  }
+
+  autovector<ColumnFamilyData*> cfds;
  if (cfd_picked != nullptr) {
-    status = SwitchMemtable(cfd_picked, write_context,
-                            FlushReason::kWriteBufferFull);
-    if (status.ok()) {
-      cfd_picked->imm()->FlushRequested();
-      SchedulePendingFlush(cfd_picked, FlushReason::kWriteBufferFull);
-      MaybeScheduleFlushOrCompaction();
+    cfds.push_back(cfd_picked);
+  }
+  FlushRequest flush_req;
+  for (const auto cfd : cfds) {
+    cfd->Ref();
+    status = SwitchMemtable(cfd, write_context);
+    cfd->Unref();
+    if (!status.ok()) {
+      break;
    }
+    uint64_t flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+    cfd->imm()->FlushRequested();
+    flush_req.emplace_back(cfd, flush_memtable_id);
+  }
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
+    MaybeScheduleFlushOrCompaction();
  }
  return status;
 }
@@ -1146,10 +1162,14 @@ Status DBImpl::DelayWrite(uint64_t num_bytes,
    uint64_t delay = write_controller_.GetDelay(env_, num_bytes);
    if (delay > 0) {
      if (write_options.no_slowdown) {
-        return Status::Incomplete();
+        return Status::Incomplete("Write stall");
      }
      TEST_SYNC_POINT("DBImpl::DelayWrite:Sleep");

+      // Notify write_thread_ about the stall so it can setup a barrier and
+      // fail any pending writers with no_slowdown
+      write_thread_.BeginWriteStall();
+      TEST_SYNC_POINT("DBImpl::DelayWrite:BeginWriteStallDone");
      mutex_.Unlock();
      // We will delay the write until we have slept for delay ms or
      // we don't need a delay anymore
@@ -1166,15 +1186,25 @@ Status DBImpl::DelayWrite(uint64_t num_bytes,
        env_->SleepForMicroseconds(kDelayInterval);
      }
      mutex_.Lock();
+      write_thread_.EndWriteStall();
    }

-    while (!error_handler_.IsDBStopped() && write_controller_.IsStopped()) {
+    // Don't wait if there's a background error, even if its a soft error. We
+    // might wait here indefinitely as the background compaction may never
+    // finish successfully, resulting in the stall condition lasting
+    // indefinitely
+    while (error_handler_.GetBGError().ok() && write_controller_.IsStopped()) {
      if (write_options.no_slowdown) {
-        return Status::Incomplete();
+        return Status::Incomplete("Write stall");
      }
      delayed = true;
+
+      // Notify write_thread_ about the stall so it can setup a barrier and
+      // fail any pending writers with no_slowdown
+      write_thread_.BeginWriteStall();
      TEST_SYNC_POINT("DBImpl::DelayWrite:Wait");
      bg_cv_.Wait();
+      write_thread_.EndWriteStall();
    }
  }
  assert(!delayed || !write_options.no_slowdown);
@@ -1184,7 +1214,19 @@ Status DBImpl::DelayWrite(uint64_t num_bytes,
    RecordTick(stats_, STALL_MICROS, time_delayed);
  }

-  return error_handler_.GetBGError();
+  // If DB is not in read-only mode and write_controller is not stopping
+  // writes, we can ignore any background errors and allow the write to
+  // proceed
+  Status s;
+  if (write_controller_.IsStopped()) {
+    // If writes are still stopped, it means we bailed due to a background
+    // error
+    s = Status::Incomplete(error_handler_.GetBGError().ToString());
+  }
+  if (error_handler_.IsDBStopped()) {
+    s = error_handler_.GetBGError();
+  }
+  return s;
 }

 Status DBImpl::ThrottleLowPriWritesIfNeeded(const WriteOptions& write_options,
@@ -1219,16 +1261,28 @@ Status DBImpl::ThrottleLowPriWritesIfNeeded(const WriteOptions& write_options,

 Status DBImpl::ScheduleFlushes(WriteContext* context) {
  ColumnFamilyData* cfd;
+  FlushRequest flush_req;
+  Status status;
  while ((cfd = flush_scheduler_.TakeNextColumnFamily()) != nullptr) {
-    auto status = SwitchMemtable(cfd, context, FlushReason::kWriteBufferFull);
+    status = SwitchMemtable(cfd, context);
+    bool should_schedule = true;
    if (cfd->Unref()) {
      delete cfd;
+      should_schedule = false;
    }
    if (!status.ok()) {
-      return status;
+      break;
+    }
+    if (should_schedule) {
+      uint64_t flush_memtable_id = cfd->imm()->GetLatestMemTableID();
+      flush_req.emplace_back(cfd, flush_memtable_id);
    }
  }
-  return Status::OK();
+  if (status.ok()) {
+    SchedulePendingFlush(flush_req, FlushReason::kWriteBufferFull);
+    MaybeScheduleFlushOrCompaction();
+  }
+  return status;
 }

 #ifndef ROCKSDB_LITE
@@ -1249,8 +1303,7 @@ void DBImpl::NotifyOnMemTableSealed(ColumnFamilyData* /*cfd*/,

 // REQUIRES: mutex_ is held
 // REQUIRES: this thread is currently at the front of the writer queue
-Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
-                              FlushReason flush_reason) {
+Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context) {
  mutex_.AssertHeld();
  WriteThread::Writer nonmem_w;
  if (two_write_queues_) {
@@ -1319,6 +1372,8 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
  auto write_hint = CalculateWALWriteHint();
  mutex_.Unlock();
  {
+    std::string log_fname =
+        LogFileName(immutable_db_options_.wal_dir, new_log_number);
    if (creating_new_log) {
      EnvOptions opt_env_opt =
          env_->OptimizeForLogWrite(env_options_, db_options);
@@ -1326,14 +1381,12 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
        ROCKS_LOG_INFO(immutable_db_options_.info_log,
                       "reusing log %" PRIu64 " from recycle list\n",
                       recycle_log_number);
-        s = env_->ReuseWritableFile(
-            LogFileName(immutable_db_options_.wal_dir, new_log_number),
-            LogFileName(immutable_db_options_.wal_dir, recycle_log_number),
-            &lfile, opt_env_opt);
+        std::string old_log_fname =
+            LogFileName(immutable_db_options_.wal_dir, recycle_log_number);
+        s = env_->ReuseWritableFile(log_fname, old_log_fname, &lfile,
+                                    opt_env_opt);
      } else {
-        s = NewWritableFile(
-            env_, LogFileName(immutable_db_options_.wal_dir, new_log_number),
-            &lfile, opt_env_opt);
+        s = NewWritableFile(env_, log_fname, &lfile, opt_env_opt);
      }
      if (s.ok()) {
        // Our final size should be less than write_buffer_size
@@ -1344,7 +1397,7 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
        lfile->SetPreallocationBlockSize(preallocate_block_size);
        lfile->SetWriteLifeTimeHint(write_hint);
        unique_ptr<WritableFileWriter> file_writer(
-            new WritableFileWriter(std::move(lfile), opt_env_opt));
+            new WritableFileWriter(std::move(lfile), log_fname, opt_env_opt));
        new_log = new log::Writer(
            std::move(file_writer), new_log_number,
            immutable_db_options_.recycle_log_file_num > 0, manual_wal_flush_);
@@ -1422,7 +1475,7 @@ Status DBImpl::SwitchMemtable(ColumnFamilyData* cfd, WriteContext* context,
  new_mem->Ref();
  cfd->SetMemtable(new_mem);
  InstallSuperVersionAndScheduleWork(cfd, &context->superversion_context,
-                                     mutable_cf_options, flush_reason);
+                                     mutable_cf_options);
  if (two_write_queues_) {
    nonmem_write_thread_.ExitUnbatched(&nonmem_w);
  }
@@ -252,13 +252,14 @@ TEST_F(DBTablePropertiesTest, GetColumnFamilyNameProperty) {
 }

 TEST_F(DBTablePropertiesTest, DeletionTriggeredCompactionMarking) {
-  const int kNumKeys = 1000;
-  const int kWindowSize = 100;
-  const int kNumDelsTrigger = 90;
+  int kNumKeys = 1000;
+  int kWindowSize = 100;
+  int kNumDelsTrigger = 90;
+  std::shared_ptr<TablePropertiesCollectorFactory> compact_on_del =
+    NewCompactOnDeletionCollectorFactory(kWindowSize, kNumDelsTrigger);

  Options opts = CurrentOptions();
-  opts.table_properties_collector_factories.emplace_back(
-      NewCompactOnDeletionCollectorFactory(kWindowSize, kNumDelsTrigger));
+  opts.table_properties_collector_factories.emplace_back(compact_on_del);
  Reopen(opts);

  // add an L1 file to prevent tombstones from dropping due to obsolescence
@@ -280,6 +281,48 @@ TEST_F(DBTablePropertiesTest, DeletionTriggeredCompactionMarking) {
  dbfull()->TEST_WaitForCompact();
  ASSERT_EQ(0, NumTableFilesAtLevel(0));
  ASSERT_GT(NumTableFilesAtLevel(1), 0);
+
+  // Change the window size and deletion trigger and ensure new values take
+  // effect
+  kWindowSize = 50;
+  kNumDelsTrigger = 40;
+  static_cast<CompactOnDeletionCollectorFactory*>
+    (compact_on_del.get())->SetWindowSize(kWindowSize);
+  static_cast<CompactOnDeletionCollectorFactory*>
+    (compact_on_del.get())->SetDeletionTrigger(kNumDelsTrigger);
+  for (int i = 0; i < kNumKeys; ++i) {
+    if (i >= kNumKeys - kWindowSize &&
+        i < kNumKeys - kWindowSize + kNumDelsTrigger) {
+      Delete(Key(i));
+    } else {
+      Put(Key(i), "val");
+    }
+  }
+  Flush();
+
+  dbfull()->TEST_WaitForCompact();
+  ASSERT_EQ(0, NumTableFilesAtLevel(0));
+  ASSERT_GT(NumTableFilesAtLevel(1), 0);
+
+  // Change the window size to disable delete triggered compaction
+  kWindowSize = 0;
+  static_cast<CompactOnDeletionCollectorFactory*>
+    (compact_on_del.get())->SetWindowSize(kWindowSize);
+  static_cast<CompactOnDeletionCollectorFactory*>
+    (compact_on_del.get())->SetDeletionTrigger(kNumDelsTrigger);
+  for (int i = 0; i < kNumKeys; ++i) {
+    if (i >= kNumKeys - kWindowSize &&
+        i < kNumKeys - kWindowSize + kNumDelsTrigger) {
+      Delete(Key(i));
+    } else {
+      Put(Key(i), "val");
+    }
+  }
+  Flush();
+
+  dbfull()->TEST_WaitForCompact();
+  ASSERT_EQ(1, NumTableFilesAtLevel(0));
+
 }

 }  // namespace rocksdb
@@ -262,6 +262,196 @@ TEST_F(DBTest, SkipDelay) {
  }
 }

+TEST_F(DBTest, MixedSlowdownOptions) {
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.write_buffer_size = 100000;
+  CreateAndReopenWithCF({"pikachu"}, options);
+  std::vector<port::Thread> threads;
+  std::atomic<int> thread_num(0);
+
+  std::function<void()> write_slowdown_func = [&]() {
+    int a = thread_num.fetch_add(1);
+    std::string key = "foo" + std::to_string(a);
+    WriteOptions wo;
+    wo.no_slowdown = false;
+    ASSERT_OK(dbfull()->Put(wo, key, "bar"));
+  };
+  std::function<void()> write_no_slowdown_func = [&]() {
+    int a = thread_num.fetch_add(1);
+    std::string key = "foo" + std::to_string(a);
+    WriteOptions wo;
+    wo.no_slowdown = true;
+    ASSERT_NOK(dbfull()->Put(wo, key, "bar"));
+  };
+  // Use a small number to ensure a large delay that is still effective
+  // when we do Put
+  // TODO(myabandeh): this is time dependent and could potentially make
+  // the test flaky
+  auto token = dbfull()->TEST_write_controler().GetDelayToken(1);
+  std::atomic<int> sleep_count(0);
+  rocksdb::SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::DelayWrite:BeginWriteStallDone",
+      [&](void* /*arg*/) {
+        sleep_count.fetch_add(1);
+        if (threads.empty()) {
+          for (int i = 0; i < 2; ++i) {
+            threads.emplace_back(write_slowdown_func);
+          }
+          for (int i = 0; i < 2; ++i) {
+            threads.emplace_back(write_no_slowdown_func);
+          }
+        }
+      });
+  rocksdb::SyncPoint::GetInstance()->EnableProcessing();
+
+  WriteOptions wo;
+  wo.sync = false;
+  wo.disableWAL = false;
+  wo.no_slowdown = false;
+  dbfull()->Put(wo, "foo", "bar");
+  // We need the 2nd write to trigger delay. This is because delay is
+  // estimated based on the last write size which is 0 for the first write.
+  ASSERT_OK(dbfull()->Put(wo, "foo2", "bar2"));
+          token.reset();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+  ASSERT_GE(sleep_count.load(), 1);
+
+  wo.no_slowdown = true;
+  ASSERT_OK(dbfull()->Put(wo, "foo3", "bar"));
+}
+
+TEST_F(DBTest, MixedSlowdownOptionsInQueue) {
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.write_buffer_size = 100000;
+  CreateAndReopenWithCF({"pikachu"}, options);
+  std::vector<port::Thread> threads;
+  std::atomic<int> thread_num(0);
+
+  std::function<void()> write_no_slowdown_func = [&]() {
+    int a = thread_num.fetch_add(1);
+    std::string key = "foo" + std::to_string(a);
+    WriteOptions wo;
+    wo.no_slowdown = true;
+    ASSERT_NOK(dbfull()->Put(wo, key, "bar"));
+  };
+  // Use a small number to ensure a large delay that is still effective
+  // when we do Put
+  // TODO(myabandeh): this is time dependent and could potentially make
+  // the test flaky
+  auto token = dbfull()->TEST_write_controler().GetDelayToken(1);
+  std::atomic<int> sleep_count(0);
+  rocksdb::SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::DelayWrite:Sleep",
+      [&](void* /*arg*/) {
+        sleep_count.fetch_add(1);
+        if (threads.empty()) {
+          for (int i = 0; i < 2; ++i) {
+            threads.emplace_back(write_no_slowdown_func);
+          }
+          // Sleep for 2s to allow the threads to insert themselves into the
+          // write queue
+          env_->SleepForMicroseconds(3000000ULL);
+        }
+      });
+  std::atomic<int> wait_count(0);
+  rocksdb::SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::DelayWrite:Wait",
+      [&](void* /*arg*/) { wait_count.fetch_add(1); });
+  rocksdb::SyncPoint::GetInstance()->EnableProcessing();
+
+  WriteOptions wo;
+  wo.sync = false;
+  wo.disableWAL = false;
+  wo.no_slowdown = false;
+  dbfull()->Put(wo, "foo", "bar");
+  // We need the 2nd write to trigger delay. This is because delay is
+  // estimated based on the last write size which is 0 for the first write.
+  ASSERT_OK(dbfull()->Put(wo, "foo2", "bar2"));
+          token.reset();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+  ASSERT_EQ(sleep_count.load(), 1);
+  ASSERT_GE(wait_count.load(), 0);
+}
+
+TEST_F(DBTest, MixedSlowdownOptionsStop) {
+  Options options = CurrentOptions();
+  options.env = env_;
+  options.write_buffer_size = 100000;
+  CreateAndReopenWithCF({"pikachu"}, options);
+  std::vector<port::Thread> threads;
+  std::atomic<int> thread_num(0);
+
+  std::function<void()> write_slowdown_func = [&]() {
+    int a = thread_num.fetch_add(1);
+    std::string key = "foo" + std::to_string(a);
+    WriteOptions wo;
+    wo.no_slowdown = false;
+    ASSERT_OK(dbfull()->Put(wo, key, "bar"));
+  };
+  std::function<void()> write_no_slowdown_func = [&]() {
+    int a = thread_num.fetch_add(1);
+    std::string key = "foo" + std::to_string(a);
+    WriteOptions wo;
+    wo.no_slowdown = true;
+    ASSERT_NOK(dbfull()->Put(wo, key, "bar"));
+  };
+  std::function<void()> wakeup_writer = [&]() {
+    dbfull()->mutex_.Lock();
+    dbfull()->bg_cv_.SignalAll();
+    dbfull()->mutex_.Unlock();
+  };
+  // Use a small number to ensure a large delay that is still effective
+  // when we do Put
+  // TODO(myabandeh): this is time dependent and could potentially make
+  // the test flaky
+  auto token = dbfull()->TEST_write_controler().GetStopToken();
+  std::atomic<int> wait_count(0);
+  rocksdb::SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::DelayWrite:Wait",
+      [&](void* /*arg*/) {
+        wait_count.fetch_add(1);
+        if (threads.empty()) {
+          for (int i = 0; i < 2; ++i) {
+            threads.emplace_back(write_slowdown_func);
+          }
+          for (int i = 0; i < 2; ++i) {
+            threads.emplace_back(write_no_slowdown_func);
+          }
+          // Sleep for 2s to allow the threads to insert themselves into the
+          // write queue
+          env_->SleepForMicroseconds(3000000ULL);
+        }
+        token.reset();
+        threads.emplace_back(wakeup_writer);
+      });
+  rocksdb::SyncPoint::GetInstance()->EnableProcessing();
+
+  WriteOptions wo;
+  wo.sync = false;
+  wo.disableWAL = false;
+  wo.no_slowdown = false;
+  dbfull()->Put(wo, "foo", "bar");
+  // We need the 2nd write to trigger delay. This is because delay is
+  // estimated based on the last write size which is 0 for the first write.
+  ASSERT_OK(dbfull()->Put(wo, "foo2", "bar2"));
+          token.reset();
+
+  for (auto& t : threads) {
+    t.join();
+  }
+  ASSERT_GE(wait_count.load(), 1);
+
+  wo.no_slowdown = true;
+  ASSERT_OK(dbfull()->Put(wo, "foo3", "bar"));
+}
 #ifndef ROCKSDB_LITE

 TEST_F(DBTest, LevelLimitReopen) {
@@ -4331,7 +4521,7 @@ TEST_F(DBTest, DynamicCompactionOptions) {
  // Clean up memtable and L0. Block compaction threads. If continue to write
  // and flush memtables. We should see put stop after 8 memtable flushes
  // since level0_stop_writes_trigger = 8
-  dbfull()->TEST_FlushMemTable(true);
+  dbfull()->TEST_FlushMemTable(true, true);
  dbfull()->CompactRange(CompactRangeOptions(), nullptr, nullptr);
  // Block compaction
  test::SleepingBackgroundTask sleeping_task_low;
@@ -4344,7 +4534,7 @@ TEST_F(DBTest, DynamicCompactionOptions) {
  WriteOptions wo;
  while (count < 64) {
    ASSERT_OK(Put(Key(count), RandomString(&rnd, 1024), wo));
-    dbfull()->TEST_FlushMemTable(true);
+    dbfull()->TEST_FlushMemTable(true, true);
    count++;
    if (dbfull()->TEST_write_controler().IsStopped()) {
      sleeping_task_low.WakeUp();
@@ -4372,7 +4562,7 @@ TEST_F(DBTest, DynamicCompactionOptions) {
  count = 0;
  while (count < 64) {
    ASSERT_OK(Put(Key(count), RandomString(&rnd, 1024), wo));
-    dbfull()->TEST_FlushMemTable(true);
+    dbfull()->TEST_FlushMemTable(true, true);
    count++;
    if (dbfull()->TEST_write_controler().IsStopped()) {
      sleeping_task_low.WakeUp();
@@ -5512,7 +5702,7 @@ TEST_F(DBTest, SoftLimit) {
  for (int i = 0; i < 72; i++) {
    Put(Key(i), std::string(5000, 'x'));
    if (i % 10 == 0) {
-      Flush();
+      dbfull()->TEST_FlushMemTable(true, true);
    }
  }
  dbfull()->TEST_WaitForCompact();
@@ -5522,7 +5712,7 @@ TEST_F(DBTest, SoftLimit) {
  for (int i = 0; i < 72; i++) {
    Put(Key(i), std::string(5000, 'x'));
    if (i % 10 == 0) {
-      Flush();
+      dbfull()->TEST_FlushMemTable(true, true);
    }
  }
  dbfull()->TEST_WaitForCompact();
@@ -5541,7 +5731,7 @@ TEST_F(DBTest, SoftLimit) {
    Put(Key(i), std::string(5000, 'x'));
    Put(Key(100 - i), std::string(5000, 'x'));
    // Flush the file. File size is around 30KB.
-    Flush();
+    dbfull()->TEST_FlushMemTable(true, true);
  }
  ASSERT_TRUE(dbfull()->TEST_write_controler().NeedsDelay());
  ASSERT_TRUE(listener->CheckCondition(WriteStallCondition::kDelayed));
@@ -5576,7 +5766,7 @@ TEST_F(DBTest, SoftLimit) {
    Put(Key(10 + i), std::string(5000, 'x'));
    Put(Key(90 - i), std::string(5000, 'x'));
    // Flush the file. File size is around 30KB.
-    Flush();
+    dbfull()->TEST_FlushMemTable(true, true);
  }

  // Wake up sleep task to enable compaction to run and waits
@@ -5597,7 +5787,7 @@ TEST_F(DBTest, SoftLimit) {
    Put(Key(20 + i), std::string(5000, 'x'));
    Put(Key(80 - i), std::string(5000, 'x'));
    // Flush the file. File size is around 30KB.
-    Flush();
+    dbfull()->TEST_FlushMemTable(true, true);
  }
  // Wake up sleep task to enable compaction to run and waits
  // for it to go to sleep state again to make sure one compaction
@@ -2649,7 +2649,7 @@ TEST_F(DBTest2, PinnableSliceAndMmapReads) {
 #endif
 }

-TEST_F(DBTest2, IteratorPinnedMemory) {
+TEST_F(DBTest2, DISABLED_IteratorPinnedMemory) {
  Options options = CurrentOptions();
  options.create_if_missing = true;
  options.statistics = rocksdb::CreateDBStatistics();
@@ -451,13 +451,14 @@ Options DBTestBase::GetOptions(
    }
    case kBlockBasedTableWithPartitionedIndexFormat4: {
      table_options.format_version = 4;
-      // Format 3 changes the binary index format. Since partitioned index is a
+      // Format 4 changes the binary index format. Since partitioned index is a
      // super-set of simple indexes, we are also using kTwoLevelIndexSearch to
      // test this format.
      table_options.index_type = BlockBasedTableOptions::kTwoLevelIndexSearch;
-      // The top-level index in partition filters are also affected by format 3.
+      // The top-level index in partition filters are also affected by format 4.
      table_options.filter_policy.reset(NewBloomFilterPolicy(10, false));
      table_options.partition_filters = true;
+      table_options.index_block_restart_interval = 8;
      break;
    }
    case kBlockBasedTableWithIndexRestartInterval: {
@@ -109,8 +109,6 @@ struct OptionsOverride {
  // These will be used only if filter_policy is set
  bool partition_filters = false;
  uint64_t metadata_block_size = 1024;
-  BlockBasedTableOptions::IndexType index_type =
-      BlockBasedTableOptions::IndexType::kBinarySearch;

  // Used as a bit mask of individual enums in which to skip an XF test point
  int skip_policy = 0;
@@ -317,6 +315,9 @@ class SpecialEnv : public EnvWrapper {
        }
      }
      uint64_t GetFileSize() override { return base_->GetFileSize(); }
+      Status Allocate(uint64_t offset, uint64_t len) override {
+        return base_->Allocate(offset, len);
+      }

     private:
      SpecialEnv* env_;
@@ -370,6 +371,9 @@ class SpecialEnv : public EnvWrapper {
      bool IsSyncThreadSafe() const override {
        return env_->is_wal_sync_thread_safe_.load();
      }
+      Status Allocate(uint64_t offset, uint64_t len) override {
+        return base_->Allocate(offset, len);
+      }

     private:
      SpecialEnv* env_;
@@ -575,7 +579,7 @@ class SpecialEnv : public EnvWrapper {

  std::atomic<bool> is_wal_sync_thread_safe_{true};

-  std::atomic<size_t> compaction_readahead_size_;
+  std::atomic<size_t> compaction_readahead_size_{};
 };

 class MockTimeEnv : public EnvWrapper {
@@ -18,6 +18,15 @@ namespace rocksdb {
 class DBWALTest : public DBTestBase {
 public:
  DBWALTest() : DBTestBase("/db_wal_test") {}
+
+#if defined(ROCKSDB_PLATFORM_POSIX)
+  uint64_t GetAllocatedFileSize(std::string file_name) {
+    struct stat sbuf;
+    int err = stat(file_name.c_str(), &sbuf);
+    assert(err == 0);
+    return sbuf.st_blocks * 512;
+  }
+#endif
 };

 // A SpecialEnv enriched to give more insight about deleted files
@@ -815,7 +824,7 @@ class RecoveryTestHelper {
      unique_ptr<WritableFile> file;
      ASSERT_OK(db_options.env->NewWritableFile(fname, &file, env_options));
      unique_ptr<WritableFileWriter> file_writer(
-          new WritableFileWriter(std::move(file), env_options));
+          new WritableFileWriter(std::move(file), fname, env_options));
      current_log_writer.reset(
          new log::Writer(std::move(file_writer), current_log_number,
                          db_options.recycle_log_file_num > 0));
@@ -1329,6 +1338,99 @@ TEST_F(DBWALTest, RecoverFromCorruptedWALWithoutFlush) {
  }
 }

+// Tests that total log size is recovered if we set
+// avoid_flush_during_recovery=true.
+// Flush should trigger if max_total_wal_size is reached.
+TEST_F(DBWALTest, RestoreTotalLogSizeAfterRecoverWithoutFlush) {
+  class TestFlushListener : public EventListener {
+   public:
+    std::atomic<int> count{0};
+
+    TestFlushListener() = default;
+
+    void OnFlushBegin(DB* /*db*/, const FlushJobInfo& flush_job_info) override {
+      count++;
+      assert(FlushReason::kWriteBufferManager == flush_job_info.flush_reason);
+    }
+  };
+  std::shared_ptr<TestFlushListener> test_listener =
+      std::make_shared<TestFlushListener>();
+
+  constexpr size_t kKB = 1024;
+  constexpr size_t kMB = 1024 * 1024;
+  Options options = CurrentOptions();
+  options.avoid_flush_during_recovery = true;
+  options.max_total_wal_size = 1 * kMB;
+  options.listeners.push_back(test_listener);
+  // Have to open DB in multi-CF mode to trigger flush when
+  // max_total_wal_size is reached.
+  CreateAndReopenWithCF({"one"}, options);
+  // Write some keys and we will end up with one log file which is slightly
+  // smaller than 1MB.
+  std::string value_100k(100 * kKB, 'v');
+  std::string value_300k(300 * kKB, 'v');
+  ASSERT_OK(Put(0, "foo", "v1"));
+  for (int i = 0; i < 9; i++) {
+    ASSERT_OK(Put(1, "key" + ToString(i), value_100k));
+  }
+  // Get log files before reopen.
+  VectorLogPtr log_files_before;
+  ASSERT_OK(dbfull()->GetSortedWalFiles(log_files_before));
+  ASSERT_EQ(1, log_files_before.size());
+  uint64_t log_size_before = log_files_before[0]->SizeFileBytes();
+  ASSERT_GT(log_size_before, 900 * kKB);
+  ASSERT_LT(log_size_before, 1 * kMB);
+  ReopenWithColumnFamilies({"default", "one"}, options);
+  // Write one more value to make log larger than 1MB.
+  ASSERT_OK(Put(1, "bar", value_300k));
+  // Get log files again. A new log file will be opened.
+  VectorLogPtr log_files_after_reopen;
+  ASSERT_OK(dbfull()->GetSortedWalFiles(log_files_after_reopen));
+  ASSERT_EQ(2, log_files_after_reopen.size());
+  ASSERT_EQ(log_files_before[0]->LogNumber(),
+            log_files_after_reopen[0]->LogNumber());
+  ASSERT_GT(log_files_after_reopen[0]->SizeFileBytes() +
+                log_files_after_reopen[1]->SizeFileBytes(),
+            1 * kMB);
+  // Write one more key to trigger flush.
+  ASSERT_OK(Put(0, "foo", "v2"));
+  dbfull()->TEST_WaitForFlushMemTable();
+  // Flushed two column families.
+  ASSERT_EQ(2, test_listener->count.load());
+}
+
+#if defined(ROCKSDB_PLATFORM_POSIX)
+#if defined(ROCKSDB_FALLOCATE_PRESENT)
+// Tests that we will truncate the preallocated space of the last log from
+// previous.
+TEST_F(DBWALTest, TruncateLastLogAfterRecoverWithoutFlush) {
+  constexpr size_t kKB = 1024;
+  Options options = CurrentOptions();
+  options.avoid_flush_during_recovery = true;
+  DestroyAndReopen(options);
+  size_t preallocated_size =
+      dbfull()->TEST_GetWalPreallocateBlockSize(options.write_buffer_size);
+  ASSERT_OK(Put("foo", "v1"));
+  VectorLogPtr log_files_before;
+  ASSERT_OK(dbfull()->GetSortedWalFiles(log_files_before));
+  ASSERT_EQ(1, log_files_before.size());
+  auto& file_before = log_files_before[0];
+  ASSERT_LT(file_before->SizeFileBytes(), 1 * kKB);
+  // The log file has preallocated space.
+  ASSERT_GE(GetAllocatedFileSize(dbname_ + file_before->PathName()),
+            preallocated_size);
+  Reopen(options);
+  VectorLogPtr log_files_after;
+  ASSERT_OK(dbfull()->GetSortedWalFiles(log_files_after));
+  ASSERT_EQ(1, log_files_after.size());
+  ASSERT_LT(log_files_after[0]->SizeFileBytes(), 1 * kKB);
+  // The preallocated space should be truncated.
+  ASSERT_LT(GetAllocatedFileSize(dbname_ + file_before->PathName()),
+            preallocated_size);
+}
+#endif  // ROCKSDB_FALLOCATE_PRESENT
+#endif  // ROCKSDB_PLATFORM_POSIX
+
 #endif  // ROCKSDB_LITE

 TEST_F(DBWALTest, WalTermTest) {
@@ -4,7 +4,9 @@
 //  (found in the LICENSE.Apache file in the root directory).
 //
 #include "db/error_handler.h"
+#include "db/db_impl.h"
 #include "db/event_helpers.h"
+#include "util/sst_file_manager_impl.h"

 namespace rocksdb {

@@ -33,7 +35,7 @@ std::map<std::tuple<BackgroundErrorReason, Status::Code, Status::SubCode, bool>,
        // Errors during BG flush
        {std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
                         Status::SubCode::kNoSpace, true),
-         Status::Severity::kSoftError},
+         Status::Severity::kHardError},
        {std::make_tuple(BackgroundErrorReason::kFlush, Status::Code::kIOError,
                         Status::SubCode::kNoSpace, false),
         Status::Severity::kNoError},
@@ -44,11 +46,11 @@ std::map<std::tuple<BackgroundErrorReason, Status::Code, Status::SubCode, bool>,
        {std::make_tuple(BackgroundErrorReason::kWriteCallback,
                         Status::Code::kIOError, Status::SubCode::kNoSpace,
                         true),
-         Status::Severity::kFatalError},
+         Status::Severity::kHardError},
        {std::make_tuple(BackgroundErrorReason::kWriteCallback,
                         Status::Code::kIOError, Status::SubCode::kNoSpace,
                         false),
-         Status::Severity::kFatalError},
+         Status::Severity::kHardError},
 };

 std::map<std::tuple<BackgroundErrorReason, Status::Code, bool>, Status::Severity>
@@ -118,6 +120,45 @@ std::map<std::tuple<BackgroundErrorReason, bool>, Status::Severity>
          Status::Severity::kFatalError},
 };

+void ErrorHandler::CancelErrorRecovery() {
+#ifndef ROCKSDB_LITE
+  db_mutex_->AssertHeld();
+
+  // We'll release the lock before calling sfm, so make sure no new
+  // recovery gets scheduled at that point
+  auto_recovery_ = false;
+  SstFileManagerImpl* sfm = reinterpret_cast<SstFileManagerImpl*>(
+      db_options_.sst_file_manager.get());
+  if (sfm) {
+    // This may or may not cancel a pending recovery
+    db_mutex_->Unlock();
+    bool cancelled = sfm->CancelErrorRecovery(this);
+    db_mutex_->Lock();
+    if (cancelled) {
+      recovery_in_prog_ = false;
+    }
+  }
+#endif
+}
+
+// This is the main function for looking at an error during a background
+// operation and deciding the severity, and error recovery strategy. The high
+// level algorithm is as follows -
+// 1. Classify the severity of the error based on the ErrorSeverityMap,
+//    DefaultErrorSeverityMap and DefaultReasonMap defined earlier
+// 2. Call a Status code specific override function to adjust the severity
+//    if needed. The reason for this is our ability to recover may depend on
+//    the exact options enabled in DBOptions
+// 3. Determine if auto recovery is possible. A listener notification callback
+//    is called, which can disable the auto recovery even if we decide its
+//    feasible
+// 4. For Status::NoSpace() errors, rely on SstFileManagerImpl to control
+//    the actual recovery. If no sst file manager is specified in DBOptions,
+//    a default one is allocated during DB::Open(), so there will always be
+//    one.
+// This can also get called as part of a recovery operation. In that case, we
+// also track the error seperately in recovery_error_ so we can tell in the
+// end whether recovery succeeded or not
 Status ErrorHandler::SetBGError(const Status& bg_err, BackgroundErrorReason reason) {
  db_mutex_->AssertHeld();

@@ -125,6 +166,12 @@ Status ErrorHandler::SetBGError(const Status& bg_err, BackgroundErrorReason reas
    return Status::OK();
  }

+  // Check if recovery is currently in progress. If it is, we will save this
+  // error so we can check it at the end to see if recovery succeeded or not
+  if (recovery_in_prog_ && recovery_error_.ok()) {
+    recovery_error_ = bg_err;
+  }
+
  bool paranoid = db_options_.paranoid_checks;
  Status::Severity sev = Status::Severity::kFatalError;
  Status new_bg_err;
@@ -156,15 +203,143 @@ Status ErrorHandler::SetBGError(const Status& bg_err, BackgroundErrorReason reas
  }

  new_bg_err = Status(bg_err, sev);
+
+  bool auto_recovery = auto_recovery_;
+  if (new_bg_err.severity() >= Status::Severity::kFatalError && auto_recovery) {
+    auto_recovery = false;
+    ;
+  }
+
+  // Allow some error specific overrides
+  if (new_bg_err == Status::NoSpace()) {
+    new_bg_err = OverrideNoSpaceError(new_bg_err, &auto_recovery);
+  }
+
  if (!new_bg_err.ok()) {
    Status s = new_bg_err;
-    EventHelpers::NotifyOnBackgroundError(db_options_.listeners, reason, &s, db_mutex_);
+    EventHelpers::NotifyOnBackgroundError(db_options_.listeners, reason, &s,
+                                          db_mutex_, &auto_recovery);
    if (!s.ok() && (s.severity() > bg_error_.severity())) {
      bg_error_ = s;
+    } else {
+      // This error is less severe than previously encountered error. Don't
+      // take any further action
+      return bg_error_;
    }
  }

+  if (auto_recovery) {
+    recovery_in_prog_ = true;
+
+    // Kick-off error specific recovery
+    if (bg_error_ == Status::NoSpace()) {
+      RecoverFromNoSpace();
+    }
+  }
  return bg_error_;
 }

+Status ErrorHandler::OverrideNoSpaceError(Status bg_error,
+                                          bool* auto_recovery) {
+#ifndef ROCKSDB_LITE
+  if (bg_error.severity() >= Status::Severity::kFatalError) {
+    return bg_error;
+  }
+
+  if (db_options_.sst_file_manager.get() == nullptr) {
+    // We rely on SFM to poll for enough disk space and recover
+    *auto_recovery = false;
+    return bg_error;
+  }
+
+  if (db_options_.allow_2pc &&
+      (bg_error.severity() <= Status::Severity::kSoftError)) {
+    // Don't know how to recover, as the contents of the current WAL file may
+    // be inconsistent, and it may be needed for 2PC. If 2PC is not enabled,
+    // we can just flush the memtable and discard the log
+    *auto_recovery = false;
+    return Status(bg_error, Status::Severity::kFatalError);
+  }
+
+  {
+    uint64_t free_space;
+    if (db_options_.env->GetFreeSpace(db_options_.db_paths[0].path,
+                                      &free_space) == Status::NotSupported()) {
+      *auto_recovery = false;
+    }
+  }
+
+  return bg_error;
+#else
+  (void)auto_recovery;
+  return Status(bg_error, Status::Severity::kFatalError);
+#endif
+}
+
+void ErrorHandler::RecoverFromNoSpace() {
+#ifndef ROCKSDB_LITE
+  SstFileManagerImpl* sfm =
+      reinterpret_cast<SstFileManagerImpl*>(db_options_.sst_file_manager.get());
+
+  // Inform SFM of the error, so it can kick-off the recovery
+  if (sfm) {
+    sfm->StartErrorRecovery(this, bg_error_);
+  }
+#endif
+}
+
+Status ErrorHandler::ClearBGError() {
+#ifndef ROCKSDB_LITE
+  db_mutex_->AssertHeld();
+
+  // Signal that recovery succeeded
+  if (recovery_error_.ok()) {
+    Status old_bg_error = bg_error_;
+    bg_error_ = Status::OK();
+    recovery_in_prog_ = false;
+    EventHelpers::NotifyOnErrorRecoveryCompleted(db_options_.listeners,
+                                                 old_bg_error, db_mutex_);
+  }
+  return recovery_error_;
+#else
+  return bg_error_;
+#endif
+}
+
+Status ErrorHandler::RecoverFromBGError(bool is_manual) {
+#ifndef ROCKSDB_LITE
+  InstrumentedMutexLock l(db_mutex_);
+  if (is_manual) {
+    // If its a manual recovery and there's a background recovery in progress
+    // return busy status
+    if (recovery_in_prog_) {
+      return Status::Busy();
+    }
+    recovery_in_prog_ = true;
+  }
+
+  if (bg_error_.severity() == Status::Severity::kSoftError) {
+    // Simply clear the background error and return
+    recovery_error_ = Status::OK();
+    return ClearBGError();
+  }
+
+  // Reset recovery_error_. We will use this to record any errors that happen
+  // during the recovery process. While recovering, the only operations that
+  // can generate background errors should be the flush operations
+  recovery_error_ = Status::OK();
+  Status s = db_->ResumeImpl();
+  // For manual recover, shutdown, and fatal error  cases, set
+  // recovery_in_prog_ to false. For automatic background recovery, leave it
+  // as is regardless of success or failure as it will be retried
+  if (is_manual || s.IsShutdownInProgress() ||
+      bg_error_.severity() >= Status::Severity::kFatalError) {
+    recovery_in_prog_ = false;
+  }
+  return s;
+#else
+  (void)is_manual;
+  return bg_error_;
+#endif
+}
 }
@@ -11,42 +11,65 @@

 namespace rocksdb {

+class DBImpl;
+
 class ErrorHandler {
  public:
-    ErrorHandler(const ImmutableDBOptions& db_options,
-        InstrumentedMutex* db_mutex)
-      : db_options_(db_options),
-        bg_error_(Status::OK()),
-        db_mutex_(db_mutex)
-      {}
-    ~ErrorHandler() {}
+   ErrorHandler(DBImpl* db, const ImmutableDBOptions& db_options,
+                InstrumentedMutex* db_mutex)
+       : db_(db),
+         db_options_(db_options),
+         bg_error_(Status::OK()),
+         recovery_error_(Status::OK()),
+         db_mutex_(db_mutex),
+         auto_recovery_(false),
+         recovery_in_prog_(false) {}
+   ~ErrorHandler() {}

-    Status::Severity GetErrorSeverity(BackgroundErrorReason reason,
-        Status::Code code, Status::SubCode subcode);
+   void EnableAutoRecovery() { auto_recovery_ = true; }

-    Status SetBGError(const Status& bg_err, BackgroundErrorReason reason);
+   Status::Severity GetErrorSeverity(BackgroundErrorReason reason,
+                                     Status::Code code,
+                                     Status::SubCode subcode);

-    Status GetBGError()
-    {
-      return bg_error_;
-    }
+   Status SetBGError(const Status& bg_err, BackgroundErrorReason reason);

-    void ClearBGError() {
-      bg_error_ = Status::OK();
-    }
+   Status GetBGError() { return bg_error_; }

-    bool IsDBStopped() {
-      return !bg_error_.ok();
+   Status GetRecoveryError() { return recovery_error_; }
+
+   Status ClearBGError();
+
+   bool IsDBStopped() {
+     return !bg_error_.ok() &&
+            bg_error_.severity() >= Status::Severity::kHardError;
    }

    bool IsBGWorkStopped() {
-      return !bg_error_.ok();
+      return !bg_error_.ok() &&
+             (bg_error_.severity() >= Status::Severity::kHardError ||
+              !auto_recovery_);
    }

-  private:
+    bool IsRecoveryInProgress() { return recovery_in_prog_; }
+
+    Status RecoverFromBGError(bool is_manual = false);
+    void CancelErrorRecovery();
+
+   private:
+    DBImpl* db_;
    const ImmutableDBOptions& db_options_;
    Status bg_error_;
+    // A seperate Status variable used to record any errors during the
+    // recovery process from hard errors
+    Status recovery_error_;
    InstrumentedMutex* db_mutex_;
+    // A flag indicating whether automatic recovery from errors is enabled
+    bool auto_recovery_;
+    bool recovery_in_prog_;
+
+    Status OverrideNoSpaceError(Status bg_error, bool* auto_recovery);
+    void RecoverFromNoSpace();
 };

 }
@@ -6,9 +6,12 @@
 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
+#ifndef ROCKSDB_LITE
+
 #include "db/db_test_util.h"
 #include "port/stack_trace.h"
 #include "rocksdb/perf_context.h"
+#include "rocksdb/sst_file_manager.h"
 #include "util/fault_injection_test_env.h"
 #if !defined(ROCKSDB_LITE)
 #include "util/sync_point.h"
@@ -33,36 +36,139 @@ class DBErrorHandlingEnv : public EnvWrapper {
    bool trig_io_error;
 };

+class ErrorHandlerListener : public EventListener {
+ public:
+  ErrorHandlerListener()
+      : mutex_(),
+        cv_(&mutex_),
+        no_auto_recovery_(false),
+        recovery_complete_(false),
+        file_creation_started_(false),
+        override_bg_error_(false),
+        file_count_(0),
+        fault_env_(nullptr) {}
+
+  void OnTableFileCreationStarted(
+      const TableFileCreationBriefInfo& /*ti*/) override {
+    InstrumentedMutexLock l(&mutex_);
+    file_creation_started_ = true;
+    if (file_count_ > 0) {
+      if (--file_count_ == 0) {
+        fault_env_->SetFilesystemActive(false, file_creation_error_);
+        file_creation_error_ = Status::OK();
+      }
+    }
+    cv_.SignalAll();
+  }
+
+  void OnErrorRecoveryBegin(BackgroundErrorReason /*reason*/,
+                            Status /*bg_error*/,
+                            bool* auto_recovery) override {
+    if (*auto_recovery && no_auto_recovery_) {
+      *auto_recovery = false;
+    }
+  }
+
+  void OnErrorRecoveryCompleted(Status /*old_bg_error*/) override {
+    InstrumentedMutexLock l(&mutex_);
+    recovery_complete_ = true;
+    cv_.SignalAll();
+  }
+
+  bool WaitForRecovery(uint64_t /*abs_time_us*/) {
+    InstrumentedMutexLock l(&mutex_);
+    while (!recovery_complete_) {
+      cv_.Wait(/*abs_time_us*/);
+    }
+    if (recovery_complete_) {
+      recovery_complete_ = false;
+      return true;
+    }
+    return false;
+  }
+
+  void WaitForTableFileCreationStarted(uint64_t /*abs_time_us*/) {
+    InstrumentedMutexLock l(&mutex_);
+    while (!file_creation_started_) {
+      cv_.Wait(/*abs_time_us*/);
+    }
+    file_creation_started_ = false;
+  }
+
+  void OnBackgroundError(BackgroundErrorReason /*reason*/,
+                         Status* bg_error) override {
+    if (override_bg_error_) {
+      *bg_error = bg_error_;
+      override_bg_error_ = false;
+    }
+  }
+
+  void EnableAutoRecovery(bool enable = true) { no_auto_recovery_ = !enable; }
+
+  void OverrideBGError(Status bg_err) {
+    bg_error_ = bg_err;
+    override_bg_error_ = true;
+  }
+
+  void InjectFileCreationError(FaultInjectionTestEnv* env, int file_count,
+                               Status s) {
+    fault_env_ = env;
+    file_count_ = file_count;
+    file_creation_error_ = s;
+  }
+
+ private:
+  InstrumentedMutex mutex_;
+  InstrumentedCondVar cv_;
+  bool no_auto_recovery_;
+  bool recovery_complete_;
+  bool file_creation_started_;
+  bool override_bg_error_;
+  int file_count_;
+  Status file_creation_error_;
+  Status bg_error_;
+  FaultInjectionTestEnv* fault_env_;
+};
+
 TEST_F(DBErrorHandlingTest, FLushWriteError) {
  std::unique_ptr<FaultInjectionTestEnv> fault_env(
      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
  Options options = GetDefaultOptions();
  options.create_if_missing = true;
  options.env = fault_env.get();
+  options.listeners.emplace_back(listener);
  Status s;
+
+  listener->EnableAutoRecovery(false);
  DestroyAndReopen(options);

-  Put(Key(0), "va;");
+  Put(Key(0), "val");
  SyncPoint::GetInstance()->SetCallBack(
      "FlushJob::Start", [&](void *) {
    fault_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
  });
  SyncPoint::GetInstance()->EnableProcessing();
  s = Flush();
-  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kSoftError);
+  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kHardError);
+  SyncPoint::GetInstance()->DisableProcessing();
  fault_env->SetFilesystemActive(true);
  s = dbfull()->Resume();
  ASSERT_EQ(s, Status::OK());

+  Reopen(options);
+  ASSERT_EQ("val", Get(Key(0)));
  Destroy(options);
 }

 TEST_F(DBErrorHandlingTest, CompactionWriteError) {
  std::unique_ptr<FaultInjectionTestEnv> fault_env(
      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
  Options options = GetDefaultOptions();
  options.create_if_missing = true;
  options.level0_file_num_compaction_trigger = 2;
+  options.listeners.emplace_back(listener);
  options.env = fault_env.get();
  Status s;
  DestroyAndReopen(options);
@@ -72,6 +178,10 @@ TEST_F(DBErrorHandlingTest, CompactionWriteError) {
  s = Flush();
  ASSERT_EQ(s, Status::OK());

+  listener->OverrideBGError(
+      Status(Status::NoSpace(), Status::Severity::kHardError)
+      );
+  listener->EnableAutoRecovery(false);
  rocksdb::SyncPoint::GetInstance()->LoadDependency(
      {{"FlushMemTableFinished", "BackgroundCallCompaction:0"}});
  rocksdb::SyncPoint::GetInstance()->SetCallBack(
@@ -85,7 +195,7 @@ TEST_F(DBErrorHandlingTest, CompactionWriteError) {
  ASSERT_EQ(s, Status::OK());

  s = dbfull()->TEST_WaitForCompact();
-  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kSoftError);
+  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kHardError);

  fault_env->SetFilesystemActive(true);
  s = dbfull()->Resume();
@@ -129,6 +239,439 @@ TEST_F(DBErrorHandlingTest, CorruptionError) {
  Destroy(options);
 }

+TEST_F(DBErrorHandlingTest, AutoRecoverFlushError) {
+  std::unique_ptr<FaultInjectionTestEnv> fault_env(
+      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
+  Options options = GetDefaultOptions();
+  options.create_if_missing = true;
+  options.env = fault_env.get();
+  options.listeners.emplace_back(listener);
+  Status s;
+
+  listener->EnableAutoRecovery();
+  DestroyAndReopen(options);
+
+  Put(Key(0), "val");
+  SyncPoint::GetInstance()->SetCallBack("FlushJob::Start", [&](void*) {
+    fault_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
+  });
+  SyncPoint::GetInstance()->EnableProcessing();
+  s = Flush();
+  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kHardError);
+  SyncPoint::GetInstance()->DisableProcessing();
+  fault_env->SetFilesystemActive(true);
+  ASSERT_EQ(listener->WaitForRecovery(5000000), true);
+
+  s = Put(Key(1), "val");
+  ASSERT_EQ(s, Status::OK());
+
+  Reopen(options);
+  ASSERT_EQ("val", Get(Key(0)));
+  ASSERT_EQ("val", Get(Key(1)));
+  Destroy(options);
+}
+
+TEST_F(DBErrorHandlingTest, FailRecoverFlushError) {
+  std::unique_ptr<FaultInjectionTestEnv> fault_env(
+      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
+  Options options = GetDefaultOptions();
+  options.create_if_missing = true;
+  options.env = fault_env.get();
+  options.listeners.emplace_back(listener);
+  Status s;
+
+  listener->EnableAutoRecovery();
+  DestroyAndReopen(options);
+
+  Put(Key(0), "val");
+  SyncPoint::GetInstance()->SetCallBack("FlushJob::Start", [&](void*) {
+    fault_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
+  });
+  SyncPoint::GetInstance()->EnableProcessing();
+  s = Flush();
+  ASSERT_EQ(s.severity(), rocksdb::Status::Severity::kHardError);
+  // We should be able to shutdown the database while auto recovery is going
+  // on in the background
+  Close();
+  DestroyDB(dbname_, options);
+}
+
+TEST_F(DBErrorHandlingTest, WALWriteError) {
+  std::unique_ptr<FaultInjectionTestEnv> fault_env(
+      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
+  Options options = GetDefaultOptions();
+  options.create_if_missing = true;
+  options.writable_file_max_buffer_size = 32768;
+  options.env = fault_env.get();
+  options.listeners.emplace_back(listener);
+  Status s;
+  Random rnd(301);
+
+  listener->EnableAutoRecovery();
+  DestroyAndReopen(options);
+
+  {
+    WriteBatch batch;
+
+    for (auto i = 0; i<100; ++i) {
+      batch.Put(Key(i), RandomString(&rnd, 1024));
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(dbfull()->Write(wopts, &batch), Status::OK());
+  };
+
+  {
+    WriteBatch batch;
+    int write_error = 0;
+
+    for (auto i = 100; i<199; ++i) {
+      batch.Put(Key(i), RandomString(&rnd, 1024));
+    }
+
+    SyncPoint::GetInstance()->SetCallBack("WritableFileWriter::Append:BeforePrepareWrite", [&](void*) {
+      write_error++;
+      if (write_error > 2) {
+        fault_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
+      }
+    });
+    SyncPoint::GetInstance()->EnableProcessing();
+    WriteOptions wopts;
+    wopts.sync = true;
+    s = dbfull()->Write(wopts, &batch);
+    ASSERT_EQ(s, s.NoSpace());
+  }
+  SyncPoint::GetInstance()->DisableProcessing();
+  fault_env->SetFilesystemActive(true);
+  ASSERT_EQ(listener->WaitForRecovery(5000000), true);
+  for (auto i=0; i<199; ++i) {
+    if (i < 100) {
+      ASSERT_NE(Get(Key(i)), "NOT_FOUND");
+    } else {
+      ASSERT_EQ(Get(Key(i)), "NOT_FOUND");
+    }
+  }
+  Reopen(options);
+  for (auto i=0; i<199; ++i) {
+    if (i < 100) {
+      ASSERT_NE(Get(Key(i)), "NOT_FOUND");
+    } else {
+      ASSERT_EQ(Get(Key(i)), "NOT_FOUND");
+    }
+  }
+  Close();
+}
+
+TEST_F(DBErrorHandlingTest, MultiCFWALWriteError) {
+  std::unique_ptr<FaultInjectionTestEnv> fault_env(
+      new FaultInjectionTestEnv(Env::Default()));
+  std::shared_ptr<ErrorHandlerListener> listener(new ErrorHandlerListener());
+  Options options = GetDefaultOptions();
+  options.create_if_missing = true;
+  options.writable_file_max_buffer_size = 32768;
+  options.env = fault_env.get();
+  options.listeners.emplace_back(listener);
+  Status s;
+  Random rnd(301);
+
+  listener->EnableAutoRecovery();
+  CreateAndReopenWithCF({"one", "two", "three"}, options);
+
+  {
+    WriteBatch batch;
+
+    for (auto i = 1; i < 4; ++i) {
+      for (auto j = 0; j < 100; ++j) {
+        batch.Put(handles_[i], Key(j), RandomString(&rnd, 1024));
+      }
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(dbfull()->Write(wopts, &batch), Status::OK());
+  };
+
+  {
+    WriteBatch batch;
+    int write_error = 0;
+
+    // Write to one CF
+    for (auto i = 100; i < 199; ++i) {
+      batch.Put(handles_[2], Key(i), RandomString(&rnd, 1024));
+    }
+
+    SyncPoint::GetInstance()->SetCallBack(
+        "WritableFileWriter::Append:BeforePrepareWrite", [&](void*) {
+          write_error++;
+          if (write_error > 2) {
+            fault_env->SetFilesystemActive(false,
+                                           Status::NoSpace("Out of space"));
+          }
+        });
+    SyncPoint::GetInstance()->EnableProcessing();
+    WriteOptions wopts;
+    wopts.sync = true;
+    s = dbfull()->Write(wopts, &batch);
+    ASSERT_EQ(s, s.NoSpace());
+  }
+  SyncPoint::GetInstance()->DisableProcessing();
+  fault_env->SetFilesystemActive(true);
+  ASSERT_EQ(listener->WaitForRecovery(5000000), true);
+
+  for (auto i = 1; i < 4; ++i) {
+    // Every CF should have been flushed
+    ASSERT_EQ(NumTableFilesAtLevel(0, i), 1);
+  }
+
+  for (auto i = 1; i < 4; ++i) {
+    for (auto j = 0; j < 199; ++j) {
+      if (j < 100) {
+        ASSERT_NE(Get(i, Key(j)), "NOT_FOUND");
+      } else {
+        ASSERT_EQ(Get(i, Key(j)), "NOT_FOUND");
+      }
+    }
+  }
+  ReopenWithColumnFamilies({"default", "one", "two", "three"}, options);
+  for (auto i = 1; i < 4; ++i) {
+    for (auto j = 0; j < 199; ++j) {
+      if (j < 100) {
+        ASSERT_NE(Get(i, Key(j)), "NOT_FOUND");
+      } else {
+        ASSERT_EQ(Get(i, Key(j)), "NOT_FOUND");
+      }
+    }
+  }
+  Close();
+}
+
+TEST_F(DBErrorHandlingTest, MultiDBCompactionError) {
+  FaultInjectionTestEnv* def_env = new FaultInjectionTestEnv(Env::Default());
+  std::vector<std::unique_ptr<FaultInjectionTestEnv>> fault_env;
+  std::vector<Options> options;
+  std::vector<std::shared_ptr<ErrorHandlerListener>> listener;
+  std::vector<DB*> db;
+  std::shared_ptr<SstFileManager> sfm(NewSstFileManager(def_env));
+  int kNumDbInstances = 3;
+  Random rnd(301);
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    listener.emplace_back(new ErrorHandlerListener());
+    options.emplace_back(GetDefaultOptions());
+    fault_env.emplace_back(new FaultInjectionTestEnv(Env::Default()));
+    options[i].create_if_missing = true;
+    options[i].level0_file_num_compaction_trigger = 2;
+    options[i].writable_file_max_buffer_size = 32768;
+    options[i].env = fault_env[i].get();
+    options[i].listeners.emplace_back(listener[i]);
+    options[i].sst_file_manager = sfm;
+    DB* dbptr;
+    char buf[16];
+
+    listener[i]->EnableAutoRecovery();
+    // Setup for returning error for the 3rd SST, which would be level 1
+    listener[i]->InjectFileCreationError(fault_env[i].get(), 3,
+                                         Status::NoSpace("Out of space"));
+    snprintf(buf, sizeof(buf), "_%d", i);
+    DestroyDB(dbname_ + std::string(buf), options[i]);
+    ASSERT_EQ(DB::Open(options[i], dbname_ + std::string(buf), &dbptr),
+              Status::OK());
+    db.emplace_back(dbptr);
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    WriteBatch batch;
+
+    for (auto j = 0; j <= 100; ++j) {
+      batch.Put(Key(j), RandomString(&rnd, 1024));
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(db[i]->Write(wopts, &batch), Status::OK());
+    ASSERT_EQ(db[i]->Flush(FlushOptions()), Status::OK());
+  }
+
+  def_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    WriteBatch batch;
+
+    // Write to one CF
+    for (auto j = 100; j < 199; ++j) {
+      batch.Put(Key(j), RandomString(&rnd, 1024));
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(db[i]->Write(wopts, &batch), Status::OK());
+    ASSERT_EQ(db[i]->Flush(FlushOptions()), Status::OK());
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    Status s = static_cast<DBImpl*>(db[i])->TEST_WaitForCompact(true);
+    ASSERT_EQ(s.severity(), Status::Severity::kSoftError);
+    fault_env[i]->SetFilesystemActive(true);
+  }
+
+  def_env->SetFilesystemActive(true);
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    std::string prop;
+    ASSERT_EQ(listener[i]->WaitForRecovery(5000000), true);
+    EXPECT_TRUE(db[i]->GetProperty(
+        "rocksdb.num-files-at-level" + NumberToString(0), &prop));
+    EXPECT_EQ(atoi(prop.c_str()), 0);
+    EXPECT_TRUE(db[i]->GetProperty(
+        "rocksdb.num-files-at-level" + NumberToString(1), &prop));
+    EXPECT_EQ(atoi(prop.c_str()), 1);
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    char buf[16];
+    snprintf(buf, sizeof(buf), "_%d", i);
+    delete db[i];
+    fault_env[i]->SetFilesystemActive(true);
+    if (getenv("KEEP_DB")) {
+      printf("DB is still at %s%s\n", dbname_.c_str(), buf);
+    } else {
+      Status s = DestroyDB(dbname_ + std::string(buf), options[i]);
+    }
+  }
+  options.clear();
+  sfm.reset();
+  delete def_env;
+}
+
+TEST_F(DBErrorHandlingTest, MultiDBVariousErrors) {
+  FaultInjectionTestEnv* def_env = new FaultInjectionTestEnv(Env::Default());
+  std::vector<std::unique_ptr<FaultInjectionTestEnv>> fault_env;
+  std::vector<Options> options;
+  std::vector<std::shared_ptr<ErrorHandlerListener>> listener;
+  std::vector<DB*> db;
+  std::shared_ptr<SstFileManager> sfm(NewSstFileManager(def_env));
+  int kNumDbInstances = 3;
+  Random rnd(301);
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    listener.emplace_back(new ErrorHandlerListener());
+    options.emplace_back(GetDefaultOptions());
+    fault_env.emplace_back(new FaultInjectionTestEnv(Env::Default()));
+    options[i].create_if_missing = true;
+    options[i].level0_file_num_compaction_trigger = 2;
+    options[i].writable_file_max_buffer_size = 32768;
+    options[i].env = fault_env[i].get();
+    options[i].listeners.emplace_back(listener[i]);
+    options[i].sst_file_manager = sfm;
+    DB* dbptr;
+    char buf[16];
+
+    listener[i]->EnableAutoRecovery();
+    switch (i) {
+      case 0:
+        // Setup for returning error for the 3rd SST, which would be level 1
+        listener[i]->InjectFileCreationError(fault_env[i].get(), 3,
+                                             Status::NoSpace("Out of space"));
+        break;
+      case 1:
+        // Setup for returning error after the 1st SST, which would result
+        // in a hard error
+        listener[i]->InjectFileCreationError(fault_env[i].get(), 2,
+                                             Status::NoSpace("Out of space"));
+        break;
+      default:
+        break;
+    }
+    snprintf(buf, sizeof(buf), "_%d", i);
+    DestroyDB(dbname_ + std::string(buf), options[i]);
+    ASSERT_EQ(DB::Open(options[i], dbname_ + std::string(buf), &dbptr),
+              Status::OK());
+    db.emplace_back(dbptr);
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    WriteBatch batch;
+
+    for (auto j = 0; j <= 100; ++j) {
+      batch.Put(Key(j), RandomString(&rnd, 1024));
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(db[i]->Write(wopts, &batch), Status::OK());
+    ASSERT_EQ(db[i]->Flush(FlushOptions()), Status::OK());
+  }
+
+  def_env->SetFilesystemActive(false, Status::NoSpace("Out of space"));
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    WriteBatch batch;
+
+    // Write to one CF
+    for (auto j = 100; j < 199; ++j) {
+      batch.Put(Key(j), RandomString(&rnd, 1024));
+    }
+
+    WriteOptions wopts;
+    wopts.sync = true;
+    ASSERT_EQ(db[i]->Write(wopts, &batch), Status::OK());
+    if (i != 1) {
+      ASSERT_EQ(db[i]->Flush(FlushOptions()), Status::OK());
+    } else {
+      ASSERT_EQ(db[i]->Flush(FlushOptions()), Status::NoSpace());
+    }
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    Status s = static_cast<DBImpl*>(db[i])->TEST_WaitForCompact(true);
+    switch (i) {
+      case 0:
+        ASSERT_EQ(s.severity(), Status::Severity::kSoftError);
+        break;
+      case 1:
+        ASSERT_EQ(s.severity(), Status::Severity::kHardError);
+        break;
+      case 2:
+        ASSERT_EQ(s, Status::OK());
+        break;
+    }
+    fault_env[i]->SetFilesystemActive(true);
+  }
+
+  def_env->SetFilesystemActive(true);
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    std::string prop;
+    if (i < 2) {
+      ASSERT_EQ(listener[i]->WaitForRecovery(5000000), true);
+    }
+    if (i == 1) {
+      ASSERT_EQ(static_cast<DBImpl*>(db[i])->TEST_WaitForCompact(true),
+                Status::OK());
+    }
+    EXPECT_TRUE(db[i]->GetProperty(
+        "rocksdb.num-files-at-level" + NumberToString(0), &prop));
+    EXPECT_EQ(atoi(prop.c_str()), 0);
+    EXPECT_TRUE(db[i]->GetProperty(
+        "rocksdb.num-files-at-level" + NumberToString(1), &prop));
+    EXPECT_EQ(atoi(prop.c_str()), 1);
+  }
+
+  for (auto i = 0; i < kNumDbInstances; ++i) {
+    char buf[16];
+    snprintf(buf, sizeof(buf), "_%d", i);
+    fault_env[i]->SetFilesystemActive(true);
+    delete db[i];
+    if (getenv("KEEP_DB")) {
+      printf("DB is still at %s%s\n", dbname_.c_str(), buf);
+    } else {
+      DestroyDB(dbname_ + std::string(buf), options[i]);
+    }
+  }
+  options.clear();
+  delete def_env;
+}
+
 }  // namespace rocksdb

 int main(int argc, char** argv) {
@@ -136,3 +679,13 @@ int main(int argc, char** argv) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
 }
+
+#else
+#include <stdio.h>
+
+int main(int /*argc*/, char** /*argv*/) {
+  fprintf(stderr, "SKIPPED as Cuckoo table is not supported in ROCKSDB_LITE\n");
+  return 0;
+}
+
+#endif  // ROCKSDB_LITE
@@ -40,8 +40,8 @@ void EventHelpers::NotifyTableFileCreationStarted(

 void EventHelpers::NotifyOnBackgroundError(
    const std::vector<std::shared_ptr<EventListener>>& listeners,
-    BackgroundErrorReason reason, Status* bg_error,
-    InstrumentedMutex* db_mutex) {
+    BackgroundErrorReason reason, Status* bg_error, InstrumentedMutex* db_mutex,
+    bool* auto_recovery) {
 #ifndef ROCKSDB_LITE
  if (listeners.size() == 0U) {
    return;
@@ -51,6 +51,9 @@ void EventHelpers::NotifyOnBackgroundError(
  db_mutex->Unlock();
  for (auto& listener : listeners) {
    listener->OnBackgroundError(reason, bg_error);
+    if (*auto_recovery) {
+      listener->OnErrorRecoveryBegin(reason, *bg_error, auto_recovery);
+    }
  }
  db_mutex->Lock();
 #else
@@ -58,6 +61,7 @@ void EventHelpers::NotifyOnBackgroundError(
  (void)reason;
  (void)bg_error;
  (void)db_mutex;
+  (void)auto_recovery;
 #endif  // ROCKSDB_LITE
 }

@@ -167,4 +171,25 @@ void EventHelpers::LogAndNotifyTableFileDeletion(
 #endif  // !ROCKSDB_LITE
 }

+void EventHelpers::NotifyOnErrorRecoveryCompleted(
+    const std::vector<std::shared_ptr<EventListener>>& listeners,
+    Status old_bg_error, InstrumentedMutex* db_mutex) {
+#ifndef ROCKSDB_LITE
+  if (listeners.size() == 0U) {
+    return;
+  }
+  db_mutex->AssertHeld();
+  // release lock while notifying events
+  db_mutex->Unlock();
+  for (auto& listener : listeners) {
+    listener->OnErrorRecoveryCompleted(old_bg_error);
+  }
+  db_mutex->Lock();
+#else
+  (void)listeners;
+  (void)old_bg_error;
+  (void)db_mutex;
+#endif  // ROCKSDB_LITE
+}
+
 }  // namespace rocksdb
@@ -28,7 +28,7 @@ class EventHelpers {
  static void NotifyOnBackgroundError(
      const std::vector<std::shared_ptr<EventListener>>& listeners,
      BackgroundErrorReason reason, Status* bg_error,
-      InstrumentedMutex* db_mutex);
+      InstrumentedMutex* db_mutex, bool* auto_recovery);
  static void LogAndNotifyTableFileCreationFinished(
      EventLogger* event_logger,
      const std::vector<std::shared_ptr<EventListener>>& listeners,
@@ -41,6 +41,9 @@ class EventHelpers {
      uint64_t file_number, const std::string& file_path,
      const Status& status, const std::string& db_name,
      const std::vector<std::shared_ptr<EventListener>>& listeners);
+  static void NotifyOnErrorRecoveryCompleted(
+      const std::vector<std::shared_ptr<EventListener>>& listeners,
+      Status bg_error, InstrumentedMutex* db_mutex);

 private:
  static void LogAndNotifyTableFileCreation(
@@ -344,7 +344,7 @@ Status ExternalSstFileIngestionJob::GetIngestedFileInfo(
      file_to_ingest->global_seqno_offset = 0;
      return Status::Corruption("Was not able to find file global seqno field");
    }
-    file_to_ingest->global_seqno_offset = offsets_iter->second;
+    file_to_ingest->global_seqno_offset = static_cast<size_t>(offsets_iter->second);
  } else if (file_to_ingest->version == 1) {
    // SST file V1 should not have global seqno field
    assert(seqno_iter == uprops.end());
@@ -78,6 +78,8 @@ const char* GetFlushReasonString (FlushReason flush_reason) {
      return "Auto Compaction";
    case FlushReason::kManualFlush:
      return "Manual Flush";
+    case FlushReason::kErrorRecovery:
+      return "Error Recovery";
    default:
      return "Invalid";
  }
@@ -371,8 +373,8 @@ Status FlushJob::WriteLevel0Table() {
                   s.ToString().c_str(),
                   meta_.marked_for_compaction ? " (needs compaction)" : "");

-    if (output_file_directory_ != nullptr) {
-      output_file_directory_->Fsync();
+    if (s.ok() && output_file_directory_ != nullptr) {
+      s = output_file_directory_->Fsync();
    }
    TEST_SYNC_POINT("FlushJob::WriteLevel0Table");
    db_mutex_->Lock();
@@ -62,7 +62,7 @@ class FlushJobTest : public testing::Test {
        manifest, &file, env_->OptimizeForManifestWrite(env_options_));
    ASSERT_OK(s);
    unique_ptr<WritableFileWriter> file_writer(
-        new WritableFileWriter(std::move(file), EnvOptions()));
+        new WritableFileWriter(std::move(file), manifest, EnvOptions()));
    {
      log::Writer log(std::move(file_writer), 0, false);
      std::string record;
@@ -916,21 +916,13 @@ bool ForwardIterator::TEST_CheckDeletedIters(int* pdeleted_iters,
 uint32_t ForwardIterator::FindFileInRange(
    const std::vector<FileMetaData*>& files, const Slice& internal_key,
    uint32_t left, uint32_t right) {
-  while (left < right) {
-    uint32_t mid = (left + right) / 2;
-    const FileMetaData* f = files[mid];
-    if (cfd_->internal_comparator().InternalKeyComparator::Compare(
-          f->largest.Encode(), internal_key) < 0) {
-      // Key at "mid.largest" is < "target".  Therefore all
-      // files at or before "mid" are uninteresting.
-      left = mid + 1;
-    } else {
-      // Key at "mid.largest" is >= "target".  Therefore all files
-      // after "mid" are uninteresting.
-      right = mid;
-    }
-  }
-  return right;
+  auto cmp = [&](const FileMetaData* f, const Slice& key) -> bool {
+    return cfd_->internal_comparator().InternalKeyComparator::Compare(
+            f->largest.Encode(), key) < 0;
+  };
+  const auto &b = files.begin();
+  return static_cast<uint32_t>(std::lower_bound(b + left,
+                                 b + right, internal_key, cmp) - b);
 }

 void ForwardIterator::DeleteIterator(InternalIterator* iter, bool is_arena) {
@@ -417,7 +417,9 @@ TEST_F(EventListenerTest, DisableBGCompaction) {
  for (int i = 0; static_cast<int>(cf_meta.file_count) < kSlowdownTrigger * 10;
       ++i) {
    Put(1, ToString(i), std::string(10000, 'x'), WriteOptions());
-    db_->Flush(FlushOptions(), handles_[1]);
+    FlushOptions fo;
+    fo.allow_write_stall = true;
+    db_->Flush(fo, handles_[1]);
    db_->GetColumnFamilyMetaData(handles_[1], &cf_meta);
  }
  ASSERT_GE(listener->slowdown_count, kSlowdownTrigger * 9);
@@ -880,10 +882,13 @@ TEST_F(EventListenerTest, BackgroundErrorListenerFailedCompactionTest) {
  ASSERT_EQ(1, listener->counter());

  // trigger flush so compaction is triggered again; this time it succeeds
+  // The previous failed compaction may get retried automatically, so we may
+  // be left with 0 or 1 files in level 1, depending on when the retry gets
+  // scheduled
  ASSERT_OK(Put("key0", "val"));
  ASSERT_OK(dbfull()->TEST_WaitForFlushMemTable());
  ASSERT_OK(dbfull()->TEST_WaitForCompact());
-  ASSERT_EQ(0, NumTableFilesAtLevel(0));
+  ASSERT_LE(1, NumTableFilesAtLevel(0));
 }

 }  // namespace rocksdb
@@ -37,9 +37,9 @@ static const unsigned int kBlockSize = 32768;
 // Header is checksum (4 bytes), length (2 bytes), type (1 byte)
 static const int kHeaderSize = 4 + 2 + 1;

-// Recyclable header is checksum (4 bytes), type (1 byte), log number
-// (4 bytes), length (2 bytes).
-static const int kRecyclableHeaderSize = 4 + 1 + 4 + 2;
+// Recyclable header is checksum (4 bytes), length (2 bytes), type (1 byte),
+// log number (4 bytes).
+static const int kRecyclableHeaderSize = 4 + 2 + 1 + 4;

 }  // namespace log
 }  // namespace rocksdb
@@ -24,7 +24,7 @@ Reader::Reporter::~Reporter() {

 Reader::Reader(std::shared_ptr<Logger> info_log,
               unique_ptr<SequentialFileReader>&& _file, Reporter* reporter,
-               bool checksum, uint64_t initial_offset, uint64_t log_num)
+               bool checksum, uint64_t log_num)
    : info_log_(info_log),
      file_(std::move(_file)),
      reporter_(reporter),
@@ -36,7 +36,6 @@ Reader::Reader(std::shared_ptr<Logger> info_log,
      eof_offset_(0),
      last_record_offset_(0),
      end_of_buffer_offset_(0),
-      initial_offset_(initial_offset),
      log_number_(log_num),
      recycled_(false) {}

@@ -44,29 +43,6 @@ Reader::~Reader() {
  delete[] backing_store_;
 }

-bool Reader::SkipToInitialBlock() {
-  size_t initial_offset_in_block = initial_offset_ % kBlockSize;
-  uint64_t block_start_location = initial_offset_ - initial_offset_in_block;
-
-  // Don't search a block if we'd be in the trailer
-  if (initial_offset_in_block > kBlockSize - 6) {
-    block_start_location += kBlockSize;
-  }
-
-  end_of_buffer_offset_ = block_start_location;
-
-  // Skip to start of first block that can contain the initial record
-  if (block_start_location > 0) {
-    Status skip_status = file_->Skip(block_start_location);
-    if (!skip_status.ok()) {
-      ReportDrop(static_cast<size_t>(block_start_location), skip_status);
-      return false;
-    }
-  }
-
-  return true;
-}
-
 // For kAbsoluteConsistency, on clean shutdown we don't expect any error
 // in the log files.  For other modes, we can ignore only incomplete records
 // in the last log file, which are presumably due to a write in progress
@@ -76,12 +52,6 @@ bool Reader::SkipToInitialBlock() {
 // restrict the inconsistency to only the last log
 bool Reader::ReadRecord(Slice* record, std::string* scratch,
                        WALRecoveryMode wal_recovery_mode) {
-  if (last_record_offset_ < initial_offset_) {
-    if (!SkipToInitialBlock()) {
-      return false;
-    }
-  }
-
  scratch->clear();
  record->clear();
  bool in_fragmented_record = false;
@@ -299,8 +269,7 @@ void Reader::ReportCorruption(size_t bytes, const char* reason) {
 }

 void Reader::ReportDrop(size_t bytes, const Status& reason) {
-  if (reporter_ != nullptr &&
-      end_of_buffer_offset_ - buffer_.size() - bytes >= initial_offset_) {
+  if (reporter_ != nullptr) {
    reporter_->Corruption(bytes, reason);
  }
 }
@@ -317,7 +286,7 @@ bool Reader::ReadMore(size_t* drop_size, int *error) {
      read_error_ = true;
      *error = kEof;
      return false;
-    } else if (buffer_.size() < (size_t)kBlockSize) {
+    } else if (buffer_.size() < static_cast<size_t>(kBlockSize)) {
      eof_ = true;
      eof_offset_ = buffer_.size();
    }
@@ -342,7 +311,7 @@ bool Reader::ReadMore(size_t* drop_size, int *error) {
 unsigned int Reader::ReadPhysicalRecord(Slice* result, size_t* drop_size) {
  while (true) {
    // We need at least the minimum header size
-    if (buffer_.size() < (size_t)kHeaderSize) {
+    if (buffer_.size() < static_cast<size_t>(kHeaderSize)) {
      int r;
      if (!ReadMore(drop_size, &r)) {
        return r;
@@ -363,7 +332,7 @@ unsigned int Reader::ReadPhysicalRecord(Slice* result, size_t* drop_size) {
      }
      header_size = kRecyclableHeaderSize;
      // We need enough for the larger header
-      if (buffer_.size() < (size_t)kRecyclableHeaderSize) {
+      if (buffer_.size() < static_cast<size_t>(kRecyclableHeaderSize)) {
        int r;
        if (!ReadMore(drop_size, &r)) {
          return r;
@@ -417,13 +386,6 @@ unsigned int Reader::ReadPhysicalRecord(Slice* result, size_t* drop_size) {

    buffer_.remove_prefix(header_size + length);

-    // Skip physical record that started before initial_offset_
-    if (end_of_buffer_offset_ - buffer_.size() - header_size - length <
-        initial_offset_) {
-      result->clear();
-      return kBadRecord;
-    }
-
    *result = Slice(header + header_size, length);
    return type;
  }
@@ -50,14 +50,10 @@ class Reader {
  // live while this Reader is in use.
  //
  // If "checksum" is true, verify checksums if available.
-  //
-  // The Reader will start reading at the first record located at physical
-  // position >= initial_offset within the file.
  Reader(std::shared_ptr<Logger> info_log,
-  // @lint-ignore TXT2 T25377293 Grandfathered in
-	 unique_ptr<SequentialFileReader>&& file,
-         Reporter* reporter, bool checksum, uint64_t initial_offset,
-         uint64_t log_num);
+         // @lint-ignore TXT2 T25377293 Grandfathered in
+         unique_ptr<SequentialFileReader>&& file, Reporter* reporter,
+         bool checksum, uint64_t log_num);

  ~Reader();

@@ -108,9 +104,6 @@ class Reader {
  // Offset of the first location past the end of buffer_.
  uint64_t end_of_buffer_offset_;

-  // Offset at which to start looking for the first record to return
-  uint64_t const initial_offset_;
-
  // which log number this is
  uint64_t const log_number_;

@@ -124,7 +117,6 @@ class Reader {
    // Currently there are three situations in which this happens:
    // * The record has an invalid CRC (ReadPhysicalRecord reports a drop)
    // * The record is a 0-length record (No drop is reported)
-    // * The record is below constructor's initial_offset (No drop is reported)
    kBadRecord = kMaxRecordType + 2,
    // Returned when we fail to read a valid header.
    kBadHeader = kMaxRecordType + 3,
@@ -136,11 +128,6 @@ class Reader {
    kBadRecordChecksum = kMaxRecordType + 6,
  };

-  // Skips all blocks that are completely before "initial_offset_".
-  //
-  // Returns true on success. Handles reporting.
-  bool SkipToInitialBlock();
-
  // Return type, or one of the preceding special values
  unsigned int ReadPhysicalRecord(Slice* result, size_t* drop_size);

@@ -159,12 +159,12 @@ class LogTest : public ::testing::TestWithParam<int> {
  LogTest()
      : reader_contents_(),
        dest_holder_(test::GetWritableFileWriter(
-            new test::StringSink(&reader_contents_))),
+            new test::StringSink(&reader_contents_), "" /* don't care */)),
        source_holder_(test::GetSequentialFileReader(
            new StringSource(reader_contents_), "" /* file name */)),
        writer_(std::move(dest_holder_), 123, GetParam()),
-        reader_(nullptr, std::move(source_holder_), &report_, true /*checksum*/,
-                0 /*initial_offset*/, 123) {
+        reader_(nullptr, std::move(source_holder_), &report_,
+                true /* checksum */, 123 /* log_number */) {
    int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
    initial_offset_last_record_offsets_[0] = 0;
    initial_offset_last_record_offsets_[1] = header_size + 10000;
@@ -266,36 +266,6 @@ class LogTest : public ::testing::TestWithParam<int> {
    }
  }

-  void CheckOffsetPastEndReturnsNoRecords(uint64_t offset_past_end) {
-    WriteInitialOffsetLog();
-    unique_ptr<SequentialFileReader> file_reader(test::GetSequentialFileReader(
-        new StringSource(reader_contents_), "" /* fname */));
-    unique_ptr<Reader> offset_reader(
-        new Reader(nullptr, std::move(file_reader), &report_,
-                   true /*checksum*/, WrittenBytes() + offset_past_end, 123));
-    Slice record;
-    std::string scratch;
-    ASSERT_TRUE(!offset_reader->ReadRecord(&record, &scratch));
-  }
-
-  void CheckInitialOffsetRecord(uint64_t initial_offset,
-                                int expected_record_offset) {
-    WriteInitialOffsetLog();
-    unique_ptr<SequentialFileReader> file_reader(test::GetSequentialFileReader(
-        new StringSource(reader_contents_), "" /* fname */));
-    unique_ptr<Reader> offset_reader(
-        new Reader(nullptr, std::move(file_reader), &report_,
-                   true /*checksum*/, initial_offset, 123));
-    Slice record;
-    std::string scratch;
-    ASSERT_TRUE(offset_reader->ReadRecord(&record, &scratch));
-    ASSERT_EQ(initial_offset_record_sizes_[expected_record_offset],
-              record.size());
-    ASSERT_EQ(initial_offset_last_record_offsets_[expected_record_offset],
-              offset_reader->LastRecordOffset());
-    ASSERT_EQ((char)('a' + expected_record_offset), record.data()[0]);
-  }
-
 };

 size_t LogTest::initial_offset_record_sizes_[] =
@@ -590,55 +560,6 @@ TEST_P(LogTest, ErrorJoinsRecords) {
  }
 }

-TEST_P(LogTest, ReadStart) { CheckInitialOffsetRecord(0, 0); }
-
-TEST_P(LogTest, ReadSecondOneOff) { CheckInitialOffsetRecord(1, 1); }
-
-TEST_P(LogTest, ReadSecondTenThousand) { CheckInitialOffsetRecord(10000, 1); }
-
-TEST_P(LogTest, ReadSecondStart) {
-  int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
-  CheckInitialOffsetRecord(10000 + header_size, 1);
-}
-
-TEST_P(LogTest, ReadThirdOneOff) {
-  int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
-  CheckInitialOffsetRecord(10000 + header_size + 1, 2);
-}
-
-TEST_P(LogTest, ReadThirdStart) {
-  int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
-  CheckInitialOffsetRecord(20000 + 2 * header_size, 2);
-}
-
-TEST_P(LogTest, ReadFourthOneOff) {
-  int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
-  CheckInitialOffsetRecord(20000 + 2 * header_size + 1, 3);
-}
-
-TEST_P(LogTest, ReadFourthFirstBlockTrailer) {
-  CheckInitialOffsetRecord(log::kBlockSize - 4, 3);
-}
-
-TEST_P(LogTest, ReadFourthMiddleBlock) {
-  CheckInitialOffsetRecord(log::kBlockSize + 1, 3);
-}
-
-TEST_P(LogTest, ReadFourthLastBlock) {
-  CheckInitialOffsetRecord(2 * log::kBlockSize + 1, 3);
-}
-
-TEST_P(LogTest, ReadFourthStart) {
-  int header_size = GetParam() ? kRecyclableHeaderSize : kHeaderSize;
-  CheckInitialOffsetRecord(
-      2 * (header_size + 1000) + (2 * log::kBlockSize - 1000) + 3 * header_size,
-      3);
-}
-
-TEST_P(LogTest, ReadEnd) { CheckOffsetPastEndReturnsNoRecords(0); }
-
-TEST_P(LogTest, ReadPastEnd) { CheckOffsetPastEndReturnsNoRecords(5); }
-
 TEST_P(LogTest, ClearEofSingleBlock) {
  Write("foo");
  Write("bar");
@@ -718,7 +639,8 @@ TEST_P(LogTest, Recycle) {
    Write("xxxxxxxxxxxxxxxx");
  }
  unique_ptr<WritableFileWriter> dest_holder(test::GetWritableFileWriter(
-      new test::OverwritingStringSink(get_reader_contents())));
+      new test::OverwritingStringSink(get_reader_contents()),
+      "" /* don't care */));
  Writer recycle_writer(std::move(dest_holder), 123, true);
  recycle_writer.AddRecord(Slice("foooo"));
  recycle_writer.AddRecord(Slice("bar"));
@@ -18,9 +18,11 @@ namespace rocksdb {
 #ifdef ROCKSDB_JEMALLOC
 #ifdef __FreeBSD__
 #include <malloc_np.h>
-#define je_malloc_stats_print malloc_stats_print
 #else
 #include "jemalloc/jemalloc.h"
+#ifdef JEMALLOC_NO_RENAME
+#define malloc_stats_print je_malloc_stats_print
+#endif
 #endif

 typedef struct {
@@ -48,7 +50,7 @@ void DumpMallocStats(std::string* stats) {
  std::unique_ptr<char[]> buf{new char[kMallocStatusLen + 1]};
  mstat.cur = buf.get();
  mstat.end = buf.get() + kMallocStatusLen;
-  je_malloc_stats_print(GetJemallocStatus, &mstat, "");
+  malloc_stats_print(GetJemallocStatus, &mstat, "");
  stats->append(buf.get());
 }
 #else
@@ -336,6 +336,14 @@ class MemTable {
    mem_tracker_.DoneAllocating();
  }

+  // Notify the underlying storage that all data it contained has been
+  // persisted.
+  // REQUIRES: external synchronization to prevent simultaneous
+  // operations on the same MemTable.
+  void MarkFlushed() {
+    table_->MarkFlushed();
+  }
+
  // return true if the current MemTableRep supports merge operator.
  bool IsMergeOperatorSupported() const {
    return table_->IsMergeOperatorSupported();
@@ -248,6 +248,7 @@ void MemTableListVersion::Remove(MemTable* m,
  assert(refs_ == 1);  // only when refs_ == 1 is MemTableListVersion mutable
  memlist_.remove(m);

+  m->MarkFlushed();
  if (max_write_buffer_number_to_maintain_ > 0) {
    memlist_history_.push_front(m);
    TrimHistory(to_delete);
@@ -3,8 +3,7 @@
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).
 //
-#ifndef MERGE_HELPER_H
-#define MERGE_HELPER_H
+#pragma once

 #include <deque>
 #include <string>
@@ -193,5 +192,3 @@ class MergeOutputIterator {
 };

 } // namespace rocksdb
-
-#endif
@@ -469,7 +469,7 @@ void ProfileQueries(bool enabled_time = false) {
    ASSERT_GT(hist_num_memtable_checked.Average(), 0);
    // In read-only mode Get(), no super version operation is needed
    ASSERT_EQ(hist_get_post_process.Average(), 0);
-    ASSERT_EQ(hist_get_snapshot.Average(), 0);
+    ASSERT_GT(hist_get_snapshot.Average(), 0);

    ASSERT_GT(hist_mget.Average(), 0);
    ASSERT_GT(hist_mget_snapshot.Average(), 0);
@@ -76,7 +76,9 @@ class UncollapsedRangeDelMap : public RangeDelMap {
    return false;
  }

-  void AddTombstone(RangeTombstone tombstone) override { rep_.emplace(tombstone); }
+  void AddTombstone(RangeTombstone tombstone) override {
+    rep_.emplace(tombstone);
+  }

  size_t Size() const override { return rep_.size(); }

@@ -171,7 +173,9 @@ class CollapsedRangeDelMap : public RangeDelMap {
  const Comparator* ucmp_;

 public:
-  CollapsedRangeDelMap(const Comparator* ucmp) : ucmp_(ucmp) {
+  explicit CollapsedRangeDelMap(const Comparator* ucmp) 
+    : rep_(stl_wrappers::LessOfComparator(ucmp)), 
+      ucmp_(ucmp) {
    InvalidatePosition();
  }

@@ -265,22 +269,36 @@ class CollapsedRangeDelMap : public RangeDelMap {
      //     2:    c---   OR   2:    c---   OR   2:    c---   OR   2: c------
      //     1: A--C           1:                1: A------        1: C------
      //                ^                 ^                 ^                  ^
-      // Insert a new transition at the new tombstone's start point, or raise
-      // the existing transition at that point to the new tombstone's seqno.
      end_seq = prev_seq();
-      rep_[t.start_key_] = t.seq_;  // operator[] will overwrite existing entry
+      Rep::iterator pit;
+      if (it != rep_.begin() && (pit = std::prev(it)) != rep_.begin() &&
+          ucmp_->Compare(pit->first, t.start_key_) == 0 && std::prev(pit)->second == t.seq_) {
+        // The new tombstone starts at the end of an existing tombstone with an
+        // identical seqno:
+        //
+        //     3:
+        //     2: A--C---
+        //     1:
+        //                ^
+        // Merge the tombstones by removing the existing tombstone's end key.
+        it = rep_.erase(std::prev(it));
+      } else {
+        // Insert a new transition at the new tombstone's start point, or raise
+        // the existing transition at that point to the new tombstone's seqno.
+        rep_[t.start_key_] = t.seq_;  // operator[] will overwrite existing entry
+      }
    } else {
      // The new tombstone's start point is covered by an existing tombstone:
      //
-      //      3: A-----   OR    3: C------
-      //      2:   c---         2: c------
-      //                ^                  ^
+      //      3: A-----   OR    3: C------   OR
+      //      2:   c---         2: c------         2: C------
+      //                ^                  ^                  ^
      // Do nothing.
    }

    // Look at all the existing transitions that overlap the new tombstone.
    while (it != rep_.end() && ucmp_->Compare(it->first, t.end_key_) < 0) {
-      if (t.seq_ > it->second) {
+      if (t.seq_ >= it->second) {
        // The transition is to an existing tombstone that the new tombstone
        // covers. Save the covered tombstone's seqno. We'll need to return to
        // it if the new tombstone ends before the existing tombstone.
@@ -324,15 +342,29 @@ class CollapsedRangeDelMap : public RangeDelMap {
    }

    if (t.seq_ == prev_seq()) {
-      // The new tombstone is unterminated in the map:
-      //
-      //     3:             OR   3: --G       OR   3: --G   K--
-      //     2: C-------k        2:   G---k        2:   G---k
-      //                  ^                 ^               ^
-      // End it now, returning to the last seqno we covered. Because end keys
-      // are exclusive, if there's an existing transition at t.end_key_, it
-      // takes precedence over the transition that we install here.
-      rep_.emplace(t.end_key_, end_seq);  // emplace is a noop if existing entry
+      // The new tombstone is unterminated in the map.
+      if (it != rep_.end() && t.seq_ == it->second && ucmp_->Compare(it->first, t.end_key_) == 0) {
+        // The new tombstone ends at the start of another tombstone with an
+        // identical seqno. Merge the tombstones by removing the existing
+        // tombstone's start key.
+        rep_.erase(it);
+      } else if (end_seq == prev_seq() || (it != rep_.end() && end_seq == it->second)) {
+        // The new tombstone is implicitly ended because its end point is
+        // contained within an existing tombstone with the same seqno:
+        //
+        //     2: ---k--N
+        //              ^
+      } else {
+        // The new tombstone needs an explicit end point.
+        //
+        //     3:             OR   3: --G       OR   3: --G   K--
+        //     2: C-------k        2:   G---k        2:   G---k
+        //                  ^                 ^               ^
+        // Install one that returns to the last seqno we covered. Because end
+        // keys are exclusive, if there's an existing transition at t.end_key_,
+        // it takes precedence over the transition that we install here.
+        rep_.emplace(t.end_key_, end_seq);  // emplace is a noop if existing entry
+      }
    } else {
      // The new tombstone is implicitly ended because its end point is covered
      // by an existing tombstone with a higher seqno.
@@ -344,7 +376,7 @@ class CollapsedRangeDelMap : public RangeDelMap {
    }
  }

-  size_t Size() const override { return rep_.size() - 1; }
+  size_t Size() const override { return rep_.empty() ? 0 : rep_.size() - 1; }

  void InvalidatePosition() override { iter_ = rep_.end(); }

@@ -478,22 +510,22 @@ Status RangeDelAggregator::AddTombstones(
      }
    }
    if (largest != nullptr) {
-      // This is subtly correct despite the discrepancy between
-      // FileMetaData::largest being inclusive while RangeTombstone::end_key_
-      // is exclusive. A tombstone will only extend past the bounds of an
-      // sstable if its end-key is the largest key in the table. If that
-      // occurs, the largest key for the table is set based on the smallest
-      // key in the next table in the level. In that case, largest->user_key()
-      // is not actually a key in the current table and thus we can use it as
-      // the exclusive end-key for the tombstone.
-      if (icmp_.user_comparator()->Compare(
-              tombstone.end_key_, largest->user_key()) > 0) {
-        // The largest key should be a tombstone sentinel key.
-        assert(GetInternalKeySeqno(largest->Encode()) == kMaxSequenceNumber);
+      // To safely truncate the range tombstone's end key, it must extend past
+      // the largest key in the sstable (which may have been extended to the
+      // smallest key in the next sstable), and largest must be a tombstone
+      // sentinel key. A range tombstone may straddle two sstables and not be
+      // the tombstone sentinel key in the first sstable if a user-key also
+      // straddles the sstables (possible if there is a snapshot between the
+      // two versions of the user-key), in which case we cannot truncate the
+      // range tombstone.
+      if (icmp_.user_comparator()->Compare(tombstone.end_key_,
+                                           largest->user_key()) > 0 &&
+          GetInternalKeySeqno(largest->Encode()) == kMaxSequenceNumber) {
        tombstone.end_key_ = largest->user_key();
      }
    }
-    GetRangeDelMap(tombstone.seq_).AddTombstone(std::move(tombstone));
+    auto seq = tombstone.seq_;
+    GetRangeDelMap(seq).AddTombstone(std::move(tombstone));
    input->Next();
  }
  if (!first_iter) {
@@ -0,0 +1,244 @@
+//  Copyright (c) 2018-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#ifndef GFLAGS
+#include <cstdio>
+int main() {
+  fprintf(stderr, "Please install gflags to run rocksdb tools\n");
+  return 1;
+}
+#else
+
+#include <iostream>
+#include <iomanip>
+#include <memory>
+#include <random>
+#include <set>
+#include <string>
+#include <vector>
+
+#include "db/range_del_aggregator.h"
+#include "rocksdb/comparator.h"
+#include "rocksdb/env.h"
+#include "util/coding.h"
+#include "util/random.h"
+#include "util/stop_watch.h"
+#include "util/testutil.h"
+
+#include "util/gflags_compat.h"
+
+using GFLAGS_NAMESPACE::ParseCommandLineFlags;
+
+DEFINE_int32(num_range_tombstones, 1000, "number of range tombstones created");
+
+DEFINE_int32(num_runs, 10000, "number of test runs");
+
+DEFINE_int32(tombstone_start_upper_bound, 1000,
+             "exclusive upper bound on range tombstone start keys");
+
+DEFINE_int32(should_delete_upper_bound, 1000,
+             "exclusive upper bound on keys passed to ShouldDelete");
+
+DEFINE_double(tombstone_width_mean, 100.0, "average range tombstone width");
+
+DEFINE_double(tombstone_width_stddev, 0.0,
+              "standard deviation of range tombstone width");
+
+DEFINE_bool(use_collapsed, true, "use the collapsed range tombstone map");
+
+DEFINE_int32(seed, 0, "random number generator seed");
+
+DEFINE_int32(should_deletes_per_run, 1, "number of ShouldDelete calls per run");
+
+DEFINE_int32(add_tombstones_per_run, 1,
+             "number of AddTombstones calls per run");
+
+namespace {
+
+struct Stats {
+  uint64_t time_add_tombstones = 0;
+  uint64_t time_first_should_delete = 0;
+  uint64_t time_rest_should_delete = 0;
+};
+
+std::ostream& operator<<(std::ostream& os, const Stats& s) {
+  std::ios fmt_holder(nullptr);
+  fmt_holder.copyfmt(os);
+
+  os << std::left;
+  os << std::setw(25) << "AddTombstones: "
+     << s.time_add_tombstones /
+            (FLAGS_add_tombstones_per_run * FLAGS_num_runs * 1.0e3)
+     << " us\n";
+  os << std::setw(25) << "ShouldDelete (first): "
+     << s.time_first_should_delete / (FLAGS_num_runs * 1.0e3) << " us\n";
+  if (FLAGS_should_deletes_per_run > 1) {
+    os << std::setw(25) << "ShouldDelete (rest): "
+       << s.time_rest_should_delete /
+              ((FLAGS_should_deletes_per_run - 1) * FLAGS_num_runs * 1.0e3)
+       << " us\n";
+  }
+
+  os.copyfmt(fmt_holder);
+  return os;
+}
+
+}  // anonymous namespace
+
+namespace rocksdb {
+
+namespace {
+
+// A wrapper around RangeTombstones and the underlying data of its start and end
+// keys.
+struct PersistentRangeTombstone {
+  std::string start_key;
+  std::string end_key;
+  RangeTombstone tombstone;
+
+  PersistentRangeTombstone(std::string start, std::string end,
+                           SequenceNumber seq)
+      : start_key(std::move(start)), end_key(std::move(end)) {
+    tombstone = RangeTombstone(start_key, end_key, seq);
+  }
+
+  PersistentRangeTombstone() = default;
+
+  PersistentRangeTombstone(const PersistentRangeTombstone& t) { *this = t; }
+
+  PersistentRangeTombstone& operator=(const PersistentRangeTombstone& t) {
+    start_key = t.start_key;
+    end_key = t.end_key;
+    tombstone = RangeTombstone(start_key, end_key, t.tombstone.seq_);
+
+    return *this;
+  }
+
+  PersistentRangeTombstone(PersistentRangeTombstone&& t) noexcept { *this = t; }
+
+  PersistentRangeTombstone& operator=(PersistentRangeTombstone&& t) {
+    start_key = std::move(t.start_key);
+    end_key = std::move(t.end_key);
+    tombstone = RangeTombstone(start_key, end_key, t.tombstone.seq_);
+
+    return *this;
+  }
+};
+
+struct TombstoneStartKeyComparator {
+  explicit TombstoneStartKeyComparator(const Comparator* c) : cmp(c) {}
+
+  bool operator()(const RangeTombstone& a, const RangeTombstone& b) const {
+    return cmp->Compare(a.start_key_, b.start_key_) < 0;
+  }
+
+  const Comparator* cmp;
+};
+
+std::unique_ptr<InternalIterator> MakeRangeDelIterator(
+    const std::vector<PersistentRangeTombstone>& range_dels) {
+  std::vector<std::string> keys, values;
+  for (const auto& range_del : range_dels) {
+    auto key_and_value = range_del.tombstone.Serialize();
+    keys.push_back(key_and_value.first.Encode().ToString());
+    values.push_back(key_and_value.second.ToString());
+  }
+  return std::unique_ptr<test::VectorIterator>(
+      new test::VectorIterator(keys, values));
+}
+
+// convert long to a big-endian slice key
+static std::string Key(int64_t val) {
+  std::string little_endian_key;
+  std::string big_endian_key;
+  PutFixed64(&little_endian_key, val);
+  assert(little_endian_key.size() == sizeof(val));
+  big_endian_key.resize(sizeof(val));
+  for (size_t i = 0; i < sizeof(val); ++i) {
+    big_endian_key[i] = little_endian_key[sizeof(val) - 1 - i];
+  }
+  return big_endian_key;
+}
+
+}  // anonymous namespace
+
+}  // namespace rocksdb
+
+int main(int argc, char** argv) {
+  ParseCommandLineFlags(&argc, &argv, true);
+
+  Stats stats;
+  rocksdb::Random64 rnd(FLAGS_seed);
+  std::default_random_engine random_gen(FLAGS_seed);
+  std::normal_distribution<double> normal_dist(FLAGS_tombstone_width_mean,
+                                               FLAGS_tombstone_width_stddev);
+  std::vector<std::vector<rocksdb::PersistentRangeTombstone> >
+      all_persistent_range_tombstones(FLAGS_add_tombstones_per_run);
+  for (int i = 0; i < FLAGS_add_tombstones_per_run; i++) {
+    all_persistent_range_tombstones[i] =
+        std::vector<rocksdb::PersistentRangeTombstone>(
+            FLAGS_num_range_tombstones);
+  }
+  auto mode = FLAGS_use_collapsed
+                  ? rocksdb::RangeDelPositioningMode::kForwardTraversal
+                  : rocksdb::RangeDelPositioningMode::kFullScan;
+
+  for (int i = 0; i < FLAGS_num_runs; i++) {
+    auto icmp = rocksdb::InternalKeyComparator(rocksdb::BytewiseComparator());
+    rocksdb::RangeDelAggregator range_del_agg(icmp, {} /* snapshots */,
+                                              FLAGS_use_collapsed);
+
+    for (auto& persistent_range_tombstones : all_persistent_range_tombstones) {
+      // TODO(abhimadan): consider whether creating the range tombstones right
+      // before AddTombstones is artificially warming the cache compared to
+      // real workloads.
+      for (int j = 0; j < FLAGS_num_range_tombstones; j++) {
+        uint64_t start = rnd.Uniform(FLAGS_tombstone_start_upper_bound);
+        uint64_t end = start + std::max(1.0, normal_dist(random_gen));
+        persistent_range_tombstones[j] = rocksdb::PersistentRangeTombstone(
+            rocksdb::Key(start), rocksdb::Key(end), j);
+      }
+
+      auto range_del_iter =
+          rocksdb::MakeRangeDelIterator(persistent_range_tombstones);
+      rocksdb::StopWatchNano stop_watch_add_tombstones(rocksdb::Env::Default(),
+                                                       true /* auto_start */);
+      range_del_agg.AddTombstones(std::move(range_del_iter));
+      stats.time_add_tombstones += stop_watch_add_tombstones.ElapsedNanos();
+    }
+
+    rocksdb::ParsedInternalKey parsed_key;
+    parsed_key.sequence = FLAGS_num_range_tombstones / 2;
+    parsed_key.type = rocksdb::kTypeValue;
+
+    uint64_t first_key = rnd.Uniform(FLAGS_should_delete_upper_bound -
+                                     FLAGS_should_deletes_per_run + 1);
+
+    for (int j = 0; j < FLAGS_should_deletes_per_run; j++) {
+      std::string key_string = rocksdb::Key(first_key + j);
+      parsed_key.user_key = key_string;
+
+      rocksdb::StopWatchNano stop_watch_should_delete(rocksdb::Env::Default(),
+          true /* auto_start */);
+      range_del_agg.ShouldDelete(parsed_key, mode);
+      uint64_t call_time = stop_watch_should_delete.ElapsedNanos();
+
+      if (j == 0) {
+        stats.time_first_should_delete += call_time;
+      } else {
+        stats.time_rest_should_delete += call_time;
+      }
+    }
+  }
+
+  std::cout << "=========================\n"
+            << "Results:\n"
+            << "=========================\n"
+            << stats;
+
+  return 0;
+}
+
+#endif  // GFLAGS
@@ -27,7 +27,7 @@ enum Direction {
  kReverse,
 };

-static auto icmp = InternalKeyComparator(BytewiseComparator());
+static auto bytewise_icmp = InternalKeyComparator(BytewiseComparator());

 void AddTombstones(RangeDelAggregator* range_del_agg,
                   const std::vector<RangeTombstone>& range_dels,
@@ -66,8 +66,8 @@ void VerifyRangeDels(
    const std::vector<RangeTombstone>& range_dels_in,
    const std::vector<ExpectedPoint>& expected_points,
    const std::vector<RangeTombstone>& expected_collapsed_range_dels,
-    const InternalKey* smallest = nullptr,
-    const InternalKey* largest = nullptr) {
+    const InternalKey* smallest = nullptr, const InternalKey* largest = nullptr,
+    const InternalKeyComparator& icmp = bytewise_icmp) {
  // Test same result regardless of which order the range deletions are added
  // and regardless of collapsed mode.
  for (bool collapsed : {false, true}) {
@@ -164,6 +164,14 @@ TEST_F(RangeDelAggregatorTest, OverlapAboveMiddle) {
                  {{"a", "b", 5}, {"b", "c", 10}, {"c", "d", 5}});
 }

+TEST_F(RangeDelAggregatorTest, OverlapAboveMiddleReverse) {
+  VerifyRangeDels({{"d", "a", 5}, {"c", "b", 10}},
+                  {{"z", 0}, {"d", 5}, {"c", 10}, {"b", 5}, {"a", 0}},
+                  {{"d", "c", 5}, {"c", "b", 10}, {"b", "a", 5}},
+                  nullptr /* smallest */, nullptr /* largest */,
+                  InternalKeyComparator(ReverseBytewiseComparator()));
+}
+
 TEST_F(RangeDelAggregatorTest, OverlapFully) {
  VerifyRangeDels({{"a", "d", 10}, {"b", "c", 5}},
                  {{" ", 0}, {"a", 10}, {"d", 0}}, {{"a", "d", 10}});
@@ -200,6 +208,30 @@ TEST_F(RangeDelAggregatorTest, GapsBetweenRanges) {
                  {{"a", "b", 5}, {"c", "d", 10}, {"e", "f", 15}});
 }

+TEST_F(RangeDelAggregatorTest, IdenticalSameSeqNo) {
+  VerifyRangeDels({{"a", "b", 5}, {"a", "b", 5}},
+                  {{" ", 0}, {"a", 5}, {"b", 0}},
+                  {{"a", "b", 5}});
+}
+
+TEST_F(RangeDelAggregatorTest, ContiguousSameSeqNo) {
+  VerifyRangeDels({{"a", "b", 5}, {"b", "c", 5}},
+                  {{" ", 0}, {"a", 5}, {"b", 5}, {"c", 0}},
+                  {{"a", "c", 5}});
+}
+
+TEST_F(RangeDelAggregatorTest, OverlappingSameSeqNo) {
+  VerifyRangeDels({{"a", "c", 5}, {"b", "d", 5}},
+                  {{" ", 0}, {"a", 5}, {"b", 5}, {"c", 5}, {"d", 0}},
+                  {{"a", "d", 5}});
+}
+
+TEST_F(RangeDelAggregatorTest, CoverSameSeqNo) {
+  VerifyRangeDels({{"a", "d", 5}, {"b", "c", 5}},
+                  {{" ", 0}, {"a", 5}, {"b", 5}, {"c", 5}, {"d", 0}},
+                  {{"a", "d", 5}});
+}
+
 // Note the Cover* tests also test cases where tombstones are inserted under a
 // larger one when VerifyRangeDels() runs them in reverse
 TEST_F(RangeDelAggregatorTest, CoverMultipleFromLeft) {
@@ -235,14 +267,14 @@ TEST_F(RangeDelAggregatorTest, AlternateMultipleAboveBelow) {

 TEST_F(RangeDelAggregatorTest, MergingIteratorAllEmptyStripes) {
  for (bool collapsed : {true, false}) {
-    RangeDelAggregator range_del_agg(icmp, {1, 2}, collapsed);
+    RangeDelAggregator range_del_agg(bytewise_icmp, {1, 2}, collapsed);
    VerifyRangeDelIter(range_del_agg.NewIterator().get(), {});
  }
 }

 TEST_F(RangeDelAggregatorTest, MergingIteratorOverlappingStripes) {
  for (bool collapsed : {true, false}) {
-    RangeDelAggregator range_del_agg(icmp, {5, 15, 25, 35}, collapsed);
+    RangeDelAggregator range_del_agg(bytewise_icmp, {5, 15, 25, 35}, collapsed);
    AddTombstones(
        &range_del_agg,
        {{"d", "e", 10}, {"aa", "b", 20}, {"c", "d", 30}, {"a", "b", 10}});
@@ -253,7 +285,8 @@ TEST_F(RangeDelAggregatorTest, MergingIteratorOverlappingStripes) {
 }

 TEST_F(RangeDelAggregatorTest, MergingIteratorSeek) {
-  RangeDelAggregator range_del_agg(icmp, {5, 15}, true /* collapsed */);
+  RangeDelAggregator range_del_agg(bytewise_icmp, {5, 15},
+                                   true /* collapsed */);
  AddTombstones(&range_del_agg, {{"a", "c", 10},
                                 {"b", "c", 11},
                                 {"f", "g", 10},
@@ -300,6 +333,21 @@ TEST_F(RangeDelAggregatorTest, TruncateTombstones) {
      &smallest, &largest);
 }

+TEST_F(RangeDelAggregatorTest, OverlappingLargestKeyTruncateTombstones) {
+  const InternalKey smallest("b", 1, kTypeRangeDeletion);
+  const InternalKey largest(
+      "e", 3,  // could happen if "e" is in consecutive sstables
+      kTypeValue);
+  VerifyRangeDels(
+      {{"a", "c", 10}, {"d", "f", 10}},
+      {{"a", 10, true},  // truncated
+       {"b", 10, false}, // not truncated
+       {"d", 10, false}, // not truncated
+       {"e", 10, false}}, // not truncated
+      {{"b", "c", 10}, {"d", "f", 10}},
+      &smallest, &largest);
+}
+
 }  // namespace rocksdb

 int main(int argc, char** argv) {
@@ -353,7 +353,7 @@ class Repairer {
    // propagating bad information (like overly large sequence
    // numbers).
    log::Reader reader(db_options_.info_log, std::move(lfile_reader), &reporter,
-                       true /*enable checksum*/, 0 /*initial_offset*/, log);
+                       true /*enable checksum*/, log);

    // Initialize per-column family memtables
    for (auto* cfd : *vset_.GetColumnFamilySet()) {
@@ -74,7 +74,7 @@ TEST_F(RepairTest, CorruptManifest) {

  Close();
  ASSERT_OK(env_->FileExists(manifest_path));
-  CreateFile(env_, manifest_path, "blah");
+  CreateFile(env_, manifest_path, "blah", false /* use_fsync */);
  ASSERT_OK(RepairDB(dbname_, CurrentOptions()));
  Reopen(CurrentOptions());

@@ -153,7 +153,7 @@ TEST_F(RepairTest, CorruptSst) {
  Flush();
  auto sst_path = GetFirstSstPath();
  ASSERT_FALSE(sst_path.empty());
-  CreateFile(env_, sst_path, "blah");
+  CreateFile(env_, sst_path, "blah", false /* use_fsync */);

  Close();
  ASSERT_OK(RepairDB(dbname_, CurrentOptions()));
@@ -19,8 +19,9 @@ class SnapshotChecker {
 class DisableGCSnapshotChecker : public SnapshotChecker {
 public:
  virtual ~DisableGCSnapshotChecker() {}
-  virtual bool IsInSnapshot(SequenceNumber /*sequence*/,
-                            SequenceNumber /*snapshot_sequence*/) const override {
+  virtual bool IsInSnapshot(
+      SequenceNumber /*sequence*/,
+      SequenceNumber /*snapshot_sequence*/) const override {
    // By returning false, we prevent all the values from being GCed
    return false;
  }
@@ -46,7 +46,8 @@ void MakeBuilder(const Options& options, const ImmutableCFOptions& ioptions,
                 std::unique_ptr<WritableFileWriter>* writable,
                 std::unique_ptr<TableBuilder>* builder) {
  unique_ptr<WritableFile> wf(new test::StringSink);
-  writable->reset(new WritableFileWriter(std::move(wf), EnvOptions()));
+  writable->reset(
+      new WritableFileWriter(std::move(wf), "" /* don't care */, EnvOptions()));
  int unknown_level = -1;
  builder->reset(NewTableBuilder(
      ioptions, moptions, internal_comparator, int_tbl_prop_collector_factories,
@@ -104,7 +104,7 @@ void TransactionLogIteratorImpl::SeekToStartSequence(
  if (files_->size() <= startFileIndex) {
    return;
  }
-  Status s = OpenLogReader(files_->at(startFileIndex).get());
+  Status s = OpenLogReader(files_->at(static_cast<size_t>(startFileIndex)).get());
  if (!s.ok()) {
    currentStatus_ = s;
    reporter_.Info(currentStatus_.ToString().c_str());
@@ -312,9 +312,9 @@ Status TransactionLogIteratorImpl::OpenLogReader(const LogFile* logFile) {
    return s;
  }
  assert(file);
-  currentLogReader_.reset(new log::Reader(
-      options_->info_log, std::move(file), &reporter_,
-      read_options_.verify_checksums_, 0, logFile->LogNumber()));
+  currentLogReader_.reset(
+      new log::Reader(options_->info_log, std::move(file), &reporter_,
+                      read_options_.verify_checksums_, logFile->LogNumber()));
  return Status::OK();
 }
 }  //  namespace rocksdb
@@ -324,8 +324,6 @@ class VersionBuilder::Rep {
      // Merge the set of added files with the set of pre-existing files.
      // Drop any deleted files.  Store the result in *v.
      const auto& base_files = base_vstorage_->LevelFiles(level);
-      auto base_iter = base_files.begin();
-      auto base_end = base_files.end();
      const auto& unordered_added_files = levels_[level].added_files;
      vstorage->Reserve(level,
                        base_files.size() + unordered_added_files.size());
@@ -339,30 +337,27 @@ class VersionBuilder::Rep {
      std::sort(added_files.begin(), added_files.end(), cmp);

 #ifndef NDEBUG
-      FileMetaData* prev_file = nullptr;
-#endif
-
+      FileMetaData* prev_added_file = nullptr;
      for (const auto& added : added_files) {
-#ifndef NDEBUG
-        if (level > 0 && prev_file != nullptr) {
+        if (level > 0 && prev_added_file != nullptr) {
          assert(base_vstorage_->InternalComparator()->Compare(
-                     prev_file->smallest, added->smallest) <= 0);
+                     prev_added_file->smallest, added->smallest) <= 0);
        }
-        prev_file = added;
+        prev_added_file = added;
+      }
 #endif

-        // Add all smaller files listed in base_
-        for (auto bpos = std::upper_bound(base_iter, base_end, added, cmp);
-             base_iter != bpos; ++base_iter) {
-          MaybeAddFile(vstorage, level, *base_iter);
+      auto base_iter = base_files.begin();
+      auto base_end = base_files.end();
+      auto added_iter = added_files.begin();
+      auto added_end = added_files.end();
+      while (added_iter != added_end || base_iter != base_end) {
+        if (base_iter == base_end ||
+                (added_iter != added_end && cmp(*added_iter, *base_iter))) {
+          MaybeAddFile(vstorage, level, *added_iter++);
+        } else {
+          MaybeAddFile(vstorage, level, *base_iter++);
        }
-
-        MaybeAddFile(vstorage, level, added);
-      }
-
-      // Add remaining base files
-      for (; base_iter != base_end; ++base_iter) {
-        MaybeAddFile(vstorage, level, *base_iter);
      }
    }

@@ -21,6 +21,7 @@
 #include <string>
 #include <unordered_map>
 #include <vector>
+#include <list>
 #include "db/compaction.h"
 #include "db/internal_stats.h"
 #include "db/log_reader.h"
@@ -62,20 +63,12 @@ int FindFileInRange(const InternalKeyComparator& icmp,
    const Slice& key,
    uint32_t left,
    uint32_t right) {
-  while (left < right) {
-    uint32_t mid = (left + right) / 2;
-    const FdWithKeyRange& f = file_level.files[mid];
-    if (icmp.InternalKeyComparator::Compare(f.largest_key, key) < 0) {
-      // Key at "mid.largest" is < "target".  Therefore all
-      // files at or before "mid" are uninteresting.
-      left = mid + 1;
-    } else {
-      // Key at "mid.largest" is >= "target".  Therefore all files
-      // after "mid" are uninteresting.
-      right = mid;
-    }
-  }
-  return right;
+  auto cmp = [&](const FdWithKeyRange& f, const Slice& k) -> bool {
+    return icmp.InternalKeyComparator::Compare(f.largest_key, k) < 0;
+  };
+  const auto &b = file_level.files;
+  return static_cast<int>(std::lower_bound(b + left,
+                                           b + right, key, cmp) - b);
 }

 Status OverlapWithIterator(const Comparator* ucmp,
@@ -895,13 +888,16 @@ void Version::GetColumnFamilyMetaData(ColumnFamilyMetaData* cf_meta) {
        assert(!ioptions->cf_paths.empty());
        file_path = ioptions->cf_paths.back().path;
      }
-      files.emplace_back(
-          MakeTableFileName("", file->fd.GetNumber()), file_path,
-          file->fd.GetFileSize(), file->fd.smallest_seqno,
-          file->fd.largest_seqno, file->smallest.user_key().ToString(),
+      files.emplace_back(SstFileMetaData{
+          MakeTableFileName("", file->fd.GetNumber()),
+          file_path,
+          static_cast<size_t>(file->fd.GetFileSize()),
+          file->fd.smallest_seqno,
+          file->fd.largest_seqno,
+          file->smallest.user_key().ToString(),
          file->largest.user_key().ToString(),
          file->stats.num_reads_sampled.load(std::memory_order_relaxed),
-          file->being_compacted);
+          file->being_compacted});
      level_size += file->fd.GetFileSize();
    }
    cf_meta->levels.emplace_back(
@@ -2032,13 +2028,29 @@ bool VersionStorageInfo::OverlapInLevel(int level,
 void VersionStorageInfo::GetOverlappingInputs(
    int level, const InternalKey* begin, const InternalKey* end,
    std::vector<FileMetaData*>* inputs, int hint_index, int* file_index,
-    bool expand_range) const {
+    bool expand_range, InternalKey** next_smallest) const {
  if (level >= num_non_empty_levels_) {
    // this level is empty, no overlapping inputs
    return;
  }

  inputs->clear();
+  if (file_index) {
+    *file_index = -1;
+  }
+  const Comparator* user_cmp = user_comparator_;
+  if (level > 0) {
+    GetOverlappingInputsRangeBinarySearch(level, begin, end, inputs, hint_index,
+                                          file_index, false, next_smallest);
+    return;
+  }
+
+  if (next_smallest) {
+    // next_smallest key only makes sense for non-level 0, where files are
+    // non-overlapping
+    *next_smallest = nullptr;
+  }
+
  Slice user_begin, user_end;
  if (begin != nullptr) {
    user_begin = begin->user_key();
@@ -2046,43 +2058,52 @@ void VersionStorageInfo::GetOverlappingInputs(
  if (end != nullptr) {
    user_end = end->user_key();
  }
-  if (file_index) {
-    *file_index = -1;
-  }
-  const Comparator* user_cmp = user_comparator_;
-  if (level > 0) {
-    GetOverlappingInputsRangeBinarySearch(level, begin, end, inputs,
-                                          hint_index, file_index);
-    return;
+
+  // index stores the file index need to check.
+  std::list<size_t> index;
+  for (size_t i = 0; i < level_files_brief_[level].num_files; i++) {
+    index.emplace_back(i);
  }

-  for (size_t i = 0; i < level_files_brief_[level].num_files; ) {
-    FdWithKeyRange* f = &(level_files_brief_[level].files[i++]);
-    const Slice file_start = ExtractUserKey(f->smallest_key);
-    const Slice file_limit = ExtractUserKey(f->largest_key);
-    if (begin != nullptr && user_cmp->Compare(file_limit, user_begin) < 0) {
-      // "f" is completely before specified range; skip it
-    } else if (end != nullptr && user_cmp->Compare(file_start, user_end) > 0) {
-      // "f" is completely after specified range; skip it
-    } else {
-      inputs->push_back(files_[level][i-1]);
-      if (level == 0 && expand_range) {
-        // Level-0 files may overlap each other.  So check if the newly
-        // added file has expanded the range.  If so, restart search.
-        if (begin != nullptr && user_cmp->Compare(file_start, user_begin) < 0) {
-          user_begin = file_start;
-          inputs->clear();
-          i = 0;
-        } else if (end != nullptr
-            && user_cmp->Compare(file_limit, user_end) > 0) {
-          user_end = file_limit;
-          inputs->clear();
-          i = 0;
+  while (!index.empty()) {
+    bool found_overlapping_file = false;
+    auto iter = index.begin();
+    while (iter != index.end()) {
+      FdWithKeyRange* f = &(level_files_brief_[level].files[*iter]);
+      const Slice file_start = ExtractUserKey(f->smallest_key);
+      const Slice file_limit = ExtractUserKey(f->largest_key);
+      if (begin != nullptr && user_cmp->Compare(file_limit, user_begin) < 0) {
+        // "f" is completely before specified range; skip it
+        iter++;
+      } else if (end != nullptr && user_cmp->Compare(file_start, user_end) > 0) {
+        // "f" is completely after specified range; skip it
+        iter++;
+      } else {
+        // if overlap
+        inputs->emplace_back(files_[level][*iter]);
+        found_overlapping_file = true;
+        // record the first file index.
+        if (file_index && *file_index == -1) {
+          *file_index = static_cast<int>(*iter);
+        }
+        // the related file is overlap, erase to avoid checking again.
+        iter = index.erase(iter);
+        if (expand_range) {
+          if (begin != nullptr &&
+              user_cmp->Compare(file_start, user_begin) < 0) {
+            user_begin = file_start;
+          }
+          if (end != nullptr &&
+              user_cmp->Compare(file_limit, user_end) > 0) {
+            user_end = file_limit;
+          }
        }
-      } else if (file_index) {
-        *file_index = static_cast<int>(i) - 1;
      }
    }
+    // if all the files left are not overlap, break
+    if (!found_overlapping_file) {
+      break;
+    }
  }
 }

@@ -2183,7 +2204,7 @@ int sstableKeyCompare(const Comparator* user_cmp,
 void VersionStorageInfo::GetOverlappingInputsRangeBinarySearch(
    int level, const InternalKey* begin, const InternalKey* end,
    std::vector<FileMetaData*>* inputs, int hint_index, int* file_index,
-    bool within_interval) const {
+    bool within_interval, InternalKey** next_smallest) const {
  assert(level > 0);
  int min = 0;
  int mid = 0;
@@ -2219,6 +2240,9 @@ void VersionStorageInfo::GetOverlappingInputsRangeBinarySearch(

  // If there were no overlapping files, return immediately.
  if (!foundOverlap) {
+    if (next_smallest) {
+      next_smallest = nullptr;
+    }
    return;
  }
  // returns the index where an overlap is found
@@ -2239,6 +2263,15 @@ void VersionStorageInfo::GetOverlappingInputsRangeBinarySearch(
  for (int i = start_index; i <= end_index; i++) {
    inputs->push_back(files_[level][i]);
  }
+
+  if (next_smallest != nullptr) {
+    // Provide the next key outside the range covered by inputs
+    if (++end_index < static_cast<int>(files_[level].size())) {
+      **next_smallest = files_[level][end_index]->smallest;
+    } else {
+      *next_smallest = nullptr;
+    }
+  }
 }

 // Store in *start_index and *end_index the range of all files in
@@ -2901,16 +2934,17 @@ Status VersionSet::ProcessManifestWrites(
      // create new manifest file
      ROCKS_LOG_INFO(db_options_->info_log, "Creating manifest %" PRIu64 "\n",
                     pending_manifest_file_number_);
+      std::string descriptor_fname =
+          DescriptorFileName(dbname_, pending_manifest_file_number_);
      unique_ptr<WritableFile> descriptor_file;
-      s = NewWritableFile(
-          env_, DescriptorFileName(dbname_, pending_manifest_file_number_),
-          &descriptor_file, opt_env_opts);
+      s = NewWritableFile(env_, descriptor_fname, &descriptor_file,
+                          opt_env_opts);
      if (s.ok()) {
        descriptor_file->SetPreallocationBlockSize(
            db_options_->manifest_preallocation_size);

-        unique_ptr<WritableFileWriter> file_writer(
-            new WritableFileWriter(std::move(descriptor_file), opt_env_opts));
+        unique_ptr<WritableFileWriter> file_writer(new WritableFileWriter(
+            std::move(descriptor_file), descriptor_fname, opt_env_opts));
        descriptor_log_.reset(
            new log::Writer(std::move(file_writer), 0, false));
        s = WriteSnapshot(descriptor_log_.get());
@@ -3420,7 +3454,7 @@ Status VersionSet::Recover(
    VersionSet::LogReporter reporter;
    reporter.status = &s;
    log::Reader reader(nullptr, std::move(manifest_file_reader), &reporter,
-                       true /*checksum*/, 0 /*initial_offset*/, 0);
+                       true /* checksum */, 0 /* log_number */);
    Slice record;
    std::string scratch;
    std::vector<VersionEdit> replay_buffer;
@@ -3625,8 +3659,8 @@ Status VersionSet::ListColumnFamilies(std::vector<std::string>* column_families,
  column_family_names.insert({0, kDefaultColumnFamilyName});
  VersionSet::LogReporter reporter;
  reporter.status = &s;
-  log::Reader reader(nullptr, std::move(file_reader), &reporter, true /*checksum*/,
-                     0 /*initial_offset*/, 0);
+  log::Reader reader(nullptr, std::move(file_reader), &reporter,
+                     true /* checksum */, 0 /* log_number */);
  Slice record;
  std::string scratch;
  while (reader.ReadRecord(&record, &scratch) && s.ok()) {
@@ -3786,7 +3820,7 @@ Status VersionSet::DumpManifest(Options& options, std::string& dscname,
    VersionSet::LogReporter reporter;
    reporter.status = &s;
    log::Reader reader(nullptr, std::move(file_reader), &reporter,
-                       true /*checksum*/, 0 /*initial_offset*/, 0);
+                       true /* checksum */, 0 /* log_number */);
    Slice record;
    std::string scratch;
    while (reader.ReadRecord(&record, &scratch) && s.ok()) {
@@ -4337,7 +4371,7 @@ void VersionSet::GetLiveFilesMetaData(std::vector<LiveFileMetaData>* metadata) {
        }
        filemetadata.name = MakeTableFileName("", file->fd.GetNumber());
        filemetadata.level = level;
-        filemetadata.size = file->fd.GetFileSize();
+        filemetadata.size = static_cast<size_t>(file->fd.GetFileSize());
        filemetadata.smallestkey = file->smallest.user_key().ToString();
        filemetadata.largestkey = file->largest.user_key().ToString();
        filemetadata.smallest_seqno = file->fd.smallest_seqno;
@@ -188,9 +188,11 @@ class VersionStorageInfo {
      std::vector<FileMetaData*>* inputs,
      int hint_index = -1,        // index of overlap file
      int* file_index = nullptr,  // return index of overlap file
-      bool expand_range = true)   // if set, returns files which overlap the
-      const;                      // range and overlap each other. If false,
+      bool expand_range = true,   // if set, returns files which overlap the
+                                  // range and overlap each other. If false,
                                  // then just files intersecting the range
+      InternalKey** next_smallest = nullptr)  // if non-null, returns the
+      const;  // smallest key of next file not included
  void GetCleanInputsWithinInterval(
      int level, const InternalKey* begin,  // nullptr means before all keys
      const InternalKey* end,               // nullptr means after all keys
@@ -200,14 +202,15 @@ class VersionStorageInfo {
      const;

  void GetOverlappingInputsRangeBinarySearch(
-      int level,           // level > 0
+      int level,                 // level > 0
      const InternalKey* begin,  // nullptr means before all keys
      const InternalKey* end,    // nullptr means after all keys
      std::vector<FileMetaData*>* inputs,
      int hint_index,                // index of overlap file
      int* file_index,               // return index of overlap file
-      bool within_interval = false)  // if set, force the inputs within interval
-      const;
+      bool within_interval = false,  // if set, force the inputs within interval
+      InternalKey** next_smallest = nullptr)  // if non-null, returns the
+      const;  // smallest key of next file not included

  void ExtendFileRangeOverlappingInterval(
      int level,
@@ -566,7 +566,7 @@ class ManifestWriterTest : public testing::Test {
        manifest, &file, env_->OptimizeForManifestWrite(env_options_));
    ASSERT_OK(s);
    unique_ptr<WritableFileWriter> file_writer(
-        new WritableFileWriter(std::move(file), env_options_));
+        new WritableFileWriter(std::move(file), manifest, env_options_));
    {
      log::Writer log(std::move(file_writer), 0, false);
      std::string record;
@@ -237,7 +237,7 @@ void WalManager::PurgeObsoleteWALFiles() {
  }

  size_t const files_keep_num =
-      db_options_.wal_size_limit_mb * 1024 * 1024 / log_file_size;
+      static_cast<size_t>(db_options_.wal_size_limit_mb * 1024 * 1024 / log_file_size);
  if (log_files_num <= files_keep_num) {
    return;
  }
@@ -352,7 +352,7 @@ Status WalManager::RetainProbableWalFiles(VectorLogPtr& all_logs,
  // Binary Search. avoid opening all files.
  while (end >= start) {
    int64_t mid = start + (end - start) / 2;  // Avoid overflow.
-    SequenceNumber current_seq_num = all_logs.at(mid)->StartSequence();
+    SequenceNumber current_seq_num = all_logs.at(static_cast<size_t>(mid))->StartSequence();
    if (current_seq_num == target) {
      end = mid;
      break;
@@ -363,7 +363,7 @@ Status WalManager::RetainProbableWalFiles(VectorLogPtr& all_logs,
    }
  }
  // end could be -ve.
-  size_t start_index = std::max(static_cast<int64_t>(0), end);
+  size_t start_index = static_cast<size_t>(std::max(static_cast<int64_t>(0), end));
  // The last wal file is always included
  all_logs.erase(all_logs.begin(), all_logs.begin() + start_index);
  return Status::OK();
@@ -457,7 +457,7 @@ Status WalManager::ReadFirstLine(const std::string& fname,
  reporter.status = &status;
  reporter.ignore_error = !db_options_.paranoid_checks;
  log::Reader reader(db_options_.info_log, std::move(file_reader), &reporter,
-                     true /*checksum*/, 0 /*initial_offset*/, number);
+                     true /*checksum*/, number);
  std::string scratch;
  Slice record;

@@ -79,7 +79,7 @@ class WalManagerTest : public testing::Test {
    unique_ptr<WritableFile> file;
    ASSERT_OK(env_->NewWritableFile(fname, &file, env_options_));
    unique_ptr<WritableFileWriter> file_writer(
-        new WritableFileWriter(std::move(file), env_options_));
+        new WritableFileWriter(std::move(file), fname, env_options_));
    current_log_writer_.reset(new log::Writer(std::move(file_writer), 0, false));
  }

@@ -130,7 +130,7 @@ TEST_F(WalManagerTest, ReadFirstRecordCache) {
  ASSERT_EQ(s, 0U);

  unique_ptr<WritableFileWriter> file_writer(
-      new WritableFileWriter(std::move(file), EnvOptions()));
+      new WritableFileWriter(std::move(file), path, EnvOptions()));
  log::Writer writer(std::move(file_writer), 1,
                     db_options_.recycle_log_file_num > 0);
  WriteBatch batch;
@@ -24,7 +24,10 @@ WriteThread::WriteThread(const ImmutableDBOptions& db_options)
      enable_pipelined_write_(db_options.enable_pipelined_write),
      newest_writer_(nullptr),
      newest_memtable_writer_(nullptr),
-      last_sequence_(0) {}
+      last_sequence_(0),
+      write_stall_dummy_(),
+      stall_mu_(),
+      stall_cv_(&stall_mu_) {}

 uint8_t WriteThread::BlockingAwaitState(Writer* w, uint8_t goal_mask) {
  // We're going to block.  Lazily create the mutex.  We guarantee
@@ -219,6 +222,28 @@ bool WriteThread::LinkOne(Writer* w, std::atomic<Writer*>* newest_writer) {
  assert(w->state == STATE_INIT);
  Writer* writers = newest_writer->load(std::memory_order_relaxed);
  while (true) {
+    // If write stall in effect, and w->no_slowdown is not true,
+    // block here until stall is cleared. If its true, then return
+    // immediately
+    if (writers == &write_stall_dummy_) {
+      if (w->no_slowdown) {
+        w->status = Status::Incomplete("Write stall");
+        SetState(w, STATE_COMPLETED);
+        return false;
+      }
+      // Since no_slowdown is false, wait here to be notified of the write
+      // stall clearing
+      {
+        MutexLock lock(&stall_mu_);
+        writers = newest_writer->load(std::memory_order_relaxed);
+        if (writers == &write_stall_dummy_) {
+          stall_cv_.Wait();
+          // Load newest_writers_ again since it may have changed
+          writers = newest_writer->load(std::memory_order_relaxed);
+          continue;
+        }
+      }
+    }
    w->link_older = writers;
    if (newest_writer->compare_exchange_weak(writers, w)) {
      return (writers == nullptr);
@@ -303,12 +328,44 @@ void WriteThread::CompleteFollower(Writer* w, WriteGroup& write_group) {
  SetState(w, STATE_COMPLETED);
 }

+void WriteThread::BeginWriteStall() {
+  LinkOne(&write_stall_dummy_, &newest_writer_);
+
+  // Walk writer list until w->write_group != nullptr. The current write group
+  // will not have a mix of slowdown/no_slowdown, so its ok to stop at that
+  // point
+  Writer* w = write_stall_dummy_.link_older;
+  Writer* prev = &write_stall_dummy_;
+  while (w != nullptr && w->write_group == nullptr) {
+    if (w->no_slowdown) {
+      prev->link_older = w->link_older;
+      w->status = Status::Incomplete("Write stall");
+      SetState(w, STATE_COMPLETED);
+      w = prev->link_older;
+    } else {
+      prev = w;
+      w = w->link_older;
+    }
+  }
+}
+
+void WriteThread::EndWriteStall() {
+  MutexLock lock(&stall_mu_);
+
+  assert(newest_writer_.load(std::memory_order_relaxed) == &write_stall_dummy_);
+  newest_writer_.exchange(write_stall_dummy_.link_older);
+
+  // Wake up writers
+  stall_cv_.SignalAll();
+}
+
 static WriteThread::AdaptationContext jbg_ctx("JoinBatchGroup");
 void WriteThread::JoinBatchGroup(Writer* w) {
  TEST_SYNC_POINT_CALLBACK("WriteThread::JoinBatchGroup:Start", w);
  assert(w->batch != nullptr);

  bool linked_as_leader = LinkOne(w, &newest_writer_);
+
  if (linked_as_leader) {
    SetState(w, STATE_GROUP_LEADER);
  }
@@ -342,6 +342,13 @@ class WriteThread {
    return last_sequence_;
  }

+  // Insert a dummy writer at the tail of the write queue to indicate a write
+  // stall, and fail any writers in the queue with no_slowdown set to true
+  void BeginWriteStall();
+
+  // Remove the dummy writer and wake up waiting writers
+  void EndWriteStall();
+
 private:
  // See AwaitState.
  const uint64_t max_yield_usec_;
@@ -365,6 +372,17 @@ class WriteThread {
  // is not necessary visible to reads because the writer can be ongoing.
  SequenceNumber last_sequence_;

+  // A dummy writer to indicate a write stall condition. This will be inserted
+  // at the tail of the writer queue by the leader, so newer writers can just
+  // check for this and bail
+  Writer write_stall_dummy_;
+
+  // Mutex and condvar for writers to block on a write stall. During a write
+  // stall, writers with no_slowdown set to false will wait on this rather
+  // on the writer queue
+  port::Mutex stall_mu_;
+  port::CondVar stall_cv_;
+
  // Waits for w->state & goal_mask using w->StateMutex().  Returns
  // the state that satisfies goal_mask.
  uint8_t BlockingAwaitState(Writer* w, uint8_t goal_mask);
@@ -60,3 +60,7 @@ sagar0:
 lightmark:
  full_name: Aaron Gao
  fbid: 1351549072
+
+fgwu:
+  full_name: Fenggang Wu
+  fbid: 100002297362180
@@ -0,0 +1,118 @@
+---
+title: Improving Point-Lookup Using Data Block Hash Index
+layout: post
+author: fgwu
+category: blog
+---
+We've designed and implemented a _data block hash index_ in RocksDB that has the benefit of both reducing the CPU util and increasing the throughput for point lookup queries with a reasonable and tunable space overhead. 
+
+Specifially, we append a compact hash table to the end of the data block for efficient indexing. It is backward compatible with the data base created without this feature. After turned on the hash index feature, existing data will be gradually converted to the hash index format.
+
+Benchmarks with `db_bench`  show the CPU utilization of one of the main functions in the point lookup code path, `DataBlockIter::Seek()`, is reduced by 21.8%, and the overall RocksDB throughput is increased by 10% under purely cached workloads, at an overhead of 4.6% more space. Shadow testing with Facebook production traffic shows good CPU improvements too.
+
+
+### How to use it
+Two new options are added as part of this feature: `BlockBasedTableOptions::data_block_index_type` and `BlockBasedTableOptions::data_block_hash_table_util_ratio`.
+
+The hash index is disabled by default unless `BlockBasedTableOptions::data_block_index_type` is set to `data_block_index_type = kDataBlockBinaryAndHash`. The hash table utilization ratio is adjustable using `BlockBasedTableOptions::data_block_hash_table_util_ratio`, which is valid only if `data_block_index_type = kDataBlockBinaryAndHash`.
+
+
+```
+// the definitions can be found in include/rocksdb/table.h
+
+// The index type that will be used for the data block.
+enum DataBlockIndexType : char {
+  kDataBlockBinarySearch = 0,  // traditional block type
+  kDataBlockBinaryAndHash = 1, // additional hash index
+};
+
+// Set to kDataBlockBinaryAndHash to enable hash index
+DataBlockIndexType data_block_index_type = kDataBlockBinarySearch;
+
+// #entries/#buckets. It is valid only when data_block_hash_index_type is
+// kDataBlockBinaryAndHash.
+double data_block_hash_table_util_ratio = 0.75;
+
+```
+
+
+### Data Block Hash Index Design
+
+Current data block format groups adjacent keys together as a restart interval. One block consists of multiple restart intervals. The byte offset of the beginning of each restart interval, i.e. a restart point, is stored in an array called restart interval index or binary seek index. RocksDB does a binary search when performing point lookup for keys in data blocks to find the right restart interval the key may reside. We will use binary seek and binary search interchangeably in this post.
+
+In order to find the right location where the key may reside using binary search, multiple key parsing and comparison are needed. Each binary search branching triggers CPU cache miss, causing much CPU utilization. We have seen that this binary search takes up considerable CPU in production use-cases.
+
+![](/static/images/data-block-hash-index/block-format-binary-seek.png)
+
+We implemented a hash map at the end of the block to index the key to reduce the CPU overhead of the binary search. The hash index is just an array of pointers pointing into the binary seek index.
+
+![](/static/images/data-block-hash-index/block-format-hash-index.png)
+
+
+Each array element is considered as a hash bucket when storing the location of a key (or more precisely, the restart index of the restart interval where the key resides). When multiple keys happen to hash into the same bucket (hash collision), we just mark the bucket as “collision”. So that when later querying on that key, the hash table lookup knows that there was a hash collision happened so it can fall back to the traditional binary search to find the location of the key.
+
+We define hash table utilization ratio as the #keys/#buckets. If a utilization ratio is 0.5 and there are 100 buckets, 50 keys are stored in the bucket. The less the util ratio, the less hash collision, and the less chance for a point lookup falls back to binary seek (fall back ratio) due to the collision. So a small util ratio has more benefit to reduce the CPU time but introduces more space overhead.
+
+Space overhead depends on the util ratio. Each bucket is a `uint8_t`  (i.e. one byte). For a util ratio of 1, the space overhead is 1Byte per key, the fall back ratio observed is ~52%.
+
+![](/static/images/data-block-hash-index/hash-index-data-structure.png)
+
+### Things that Need Attention
+
+**Customized Comparator**
+
+Hash index will hash different keys (keys with different content, or byte sequence) into different hash values. This assumes the comparator will not treat different keys as equal if they have different content. 
+
+The default bytewise comparator orders the keys in alphabetical order and works well with hash index, as different keys will never be regarded as equal. However, some specially crafted comparators will do. For example, say, a `StringToIntComparator` can convert a string into an integer, and use the integer to perform the comparison. Key string “16” and “0x10” is equal to each other as seen by this `StringToIntComparator`, but they probably hash to different value. Later queries to one form of the key will not be able to find the existing key been stored in the other format.
+
+We add a new function member to the comparator interface: 
+
+```
+virtual bool CanKeysWithDifferentByteContentsBeEqual() const { return true; }
+```
+
+
+Every comparator implementation should override this function and specify the behavior of the comparator. If a comparator can regard different keys equal, the function returns true, and as a result the hash index feature will not be enabled, and vice versa.
+
+NOTE: to use the hash index feature, one should 1) have a comparator that can never treat different keys as equal; and 2) override the `CanKeysWithDifferentByteContentsBeEqual()` function to return `false`, so the hash index can be enabled.
+
+
+**Util Ratio's Impact on Data Block Cache**
+
+Adding the hash index to the end of the data block essentially takes up the data block cache space, making the effective data block cache size smaller and increasing the data block cache miss ratio. Therefore, a very small util ratio will result in a large data block cache miss ratio, and the extra I/O may drag down the throughput gain achieved by the hash index lookup. Besides, when compression is enabled, cache miss also incurs data block decompression, which is CPU-consuming. Therefore the CPU may even increase if using a too small util ratio. The best util ratio depends on workloads, cache to data ratio, disk bandwidth/latency etc. In our experiment, we found util ratio = 0.5 ~ 1 is a good range to explore that brings both CPU and throughput gains.
+
+
+### Limitations
+
+As we use `uint8_t` to store binary seek index, i.e. restart interval index, the total number of restart intervals cannot be more than 253 (we reserved  255 and 254 as special flags). For blocks having a larger number of restart intervals, the hash index will not be created and the point lookup will be done by traditional binary seek.
+
+Data block hash index only supports point lookup. We do not support range lookup. Range lookup request will fall back to BinarySeek.
+
+RocksDB supports many types of records, such as `Put`, `Delete`, `Merge`, etc (visit [here](https://github.com/facebook/rocksdb/wiki/rocksdb-basics) for more information). Currently we only support `Put` and `Delete`, but not `Merge`. Internally we have a limited set of supported record types:
+
+
+```
+kPutRecord,          <=== supported
+kDeleteRecord,       <=== supported
+kSingleDeleteRecord, <=== supported
+kTypeBlobIndex,      <=== supported
+```
+
+For records not supported, the searching process will fall back to the traditional binary seek. 
+
+
+
+### Evaluation
+To evaluate the CPU util reduction and isolate other factors such as disk I/O and block decompression, we first evaluate the hash idnex in a purely cached workload. We observe that the CPU utilization of one of the main functions in the point lookup code path, DataBlockIter::Seek(), is reduced by 21.8% and the overall throughput is increased by 10% at an overhead of 4.6% more space.
+
+However, general worload is not always purely cached. So we also evaluate the performance under different cache space pressure. In the following test, we use `db_bench` with RocksDB deployed on SSDs. The total DB size is 5~6GB, and it is about 14GB if decompressed. Different block cache sizes are used, ranging from 14GB down to 2GB, with an increasing cache miss ratio.
+
+Orange bars are representing our hash index performance. We use a hash util ratio of 1.0 in this test. Block size are set to 16KiB with the restart interval as 16.
+
+![](/static/images/data-block-hash-index/perf-throughput.png)
+![](/static/images/data-block-hash-index/perf-cache-miss.png)
+
+We can see that if cache size is greater than 8GB, hash index can bring throughput gain. Cache size greater than 8GB can be translated to a cache miss ratio smaller than 40%. So if the workload has a cache miss ratio smaller than 40%, hash index is able to increase the throughput.
+
+Besides, shadow testing with Facebook production traffic shows good CPU improvements too.
+
@@ -6,7 +6,7 @@ layout: null
  <channel>
    <title>{{ site.title | xml_escape }}</title>
    <description>{{ site.description | xml_escape }}</description>
-    <link>{{ absolute_url }}/</link>
+    <link>https://rocksdb.org/feed.xml</link>
    <atom:link href="{{ '/feed.xml' | absolute_url }}" rel="self" type="application/rss+xml"/>
    <pubDate>{{ site.time | date_to_rfc822 }}</pubDate>
    <lastBuildDate>{{ site.time | date_to_rfc822 }}</lastBuildDate>
@@ -25,6 +25,7 @@
 #include <sys/syscall.h>
 #include <sys/sysmacros.h>
 #endif
+#include <sys/statvfs.h>
 #include <sys/time.h>
 #include <sys/types.h>
 #include <time.h>
@@ -102,6 +103,18 @@ class PosixFileLock : public FileLock {
  std::string filename;
 };

+int cloexec_flags(int flags, const EnvOptions* options) {
+  // If the system supports opening the file with cloexec enabled,
+  // do so, as this avoids a race condition if a db is opened around
+  // the same time that a child process is forked
+#ifdef O_CLOEXEC
+  if (options == nullptr || options->set_fd_cloexec) {
+    flags |= O_CLOEXEC;
+  }
+#endif
+  return flags;
+}
+
 class PosixEnv : public Env {
 public:
  PosixEnv();
@@ -133,7 +146,7 @@ class PosixEnv : public Env {
                                   const EnvOptions& options) override {
    result->reset();
    int fd = -1;
-    int flags = O_RDONLY;
+    int flags = cloexec_flags(O_RDONLY, &options);
    FILE* file = nullptr;

    if (options.use_direct_reads && !options.use_mmap_reads) {
@@ -184,7 +197,8 @@ class PosixEnv : public Env {
    result->reset();
    Status s;
    int fd;
-    int flags = O_RDONLY;
+    int flags = cloexec_flags(O_RDONLY, &options);
+
    if (options.use_direct_reads && !options.use_mmap_reads) {
 #ifdef ROCKSDB_LITE
      return Status::IOError(fname, "Direct I/O not supported in RocksDB lite");
@@ -266,6 +280,8 @@ class PosixEnv : public Env {
      flags |= O_WRONLY;
    }

+    flags = cloexec_flags(flags, &options);
+
    do {
      IOSTATS_TIMER_GUARD(open_nanos);
      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
@@ -354,6 +370,8 @@ class PosixEnv : public Env {
      flags |= O_WRONLY;
    }

+    flags = cloexec_flags(flags, &options);
+
    do {
      IOSTATS_TIMER_GUARD(open_nanos);
      fd = open(old_fname.c_str(), flags,
@@ -415,9 +433,12 @@ class PosixEnv : public Env {
                                 unique_ptr<RandomRWFile>* result,
                                 const EnvOptions& options) override {
    int fd = -1;
+    int flags = cloexec_flags(O_RDWR, &options);
+
    while (fd < 0) {
      IOSTATS_TIMER_GUARD(open_nanos);
-      fd = open(fname.c_str(), O_RDWR, GetDBFileMode(allow_non_owner_access_));
+
+      fd = open(fname.c_str(), flags, GetDBFileMode(allow_non_owner_access_));
      if (fd < 0) {
        // Error while opening the file
        if (errno == EINTR) {
@@ -437,9 +458,11 @@ class PosixEnv : public Env {
      unique_ptr<MemoryMappedFileBuffer>* result) override {
    int fd = -1;
    Status status;
+    int flags = cloexec_flags(O_RDWR, nullptr);
+
    while (fd < 0) {
      IOSTATS_TIMER_GUARD(open_nanos);
-      fd = open(fname.c_str(), O_RDWR, 0644);
+      fd = open(fname.c_str(), flags, 0644);
      if (fd < 0) {
        // Error while opening the file
        if (errno == EINTR) {
@@ -477,9 +500,10 @@ class PosixEnv : public Env {
                              unique_ptr<Directory>* result) override {
    result->reset();
    int fd;
+    int flags = cloexec_flags(0, nullptr);
    {
      IOSTATS_TIMER_GUARD(open_nanos);
-      fd = open(name.c_str(), 0);
+      fd = open(name.c_str(), flags);
    }
    if (fd < 0) {
      return IOError("While open directory", name, errno);
@@ -496,7 +520,8 @@ class PosixEnv : public Env {
      return Status::OK();
    }

-    switch (errno) {
+    int err = errno;
+    switch (err) {
      case EACCES:
      case ELOOP:
      case ENAMETOOLONG:
@@ -504,8 +529,8 @@ class PosixEnv : public Env {
      case ENOTDIR:
        return Status::NotFound();
      default:
-        assert(result == EIO || result == ENOMEM);
-        return Status::IOError("Unexpected error(" + ToString(result) +
+        assert(err == EIO || err == ENOMEM);
+        return Status::IOError("Unexpected error(" + ToString(err) +
                               ") accessing file `" + fname + "' ");
    }
  }
@@ -663,9 +688,11 @@ class PosixEnv : public Env {
    }

    int fd;
+    int flags = cloexec_flags(O_RDWR | O_CREAT, nullptr);
+
    {
      IOSTATS_TIMER_GUARD(open_nanos);
-      fd = open(fname.c_str(), O_RDWR | O_CREAT, 0644);
+      fd = open(fname.c_str(), flags, 0644);
    }
    if (fd < 0) {
      result = IOError("while open a file for lock", fname, errno);
@@ -751,12 +778,30 @@ class PosixEnv : public Env {
    return gettid(pthread_self());
  }

+  virtual Status GetFreeSpace(const std::string& fname,
+                              uint64_t* free_space) override {
+    struct statvfs sbuf;
+
+    if (statvfs(fname.c_str(), &sbuf) < 0) {
+      return IOError("While doing statvfs", fname, errno);
+    }
+
+    *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bfree);
+    return Status::OK();
+  }
+
  virtual Status NewLogger(const std::string& fname,
                           shared_ptr<Logger>* result) override {
    FILE* f;
    {
      IOSTATS_TIMER_GUARD(open_nanos);
-      f = fopen(fname.c_str(), "w");
+      f = fopen(fname.c_str(), "w"
+#ifdef __GLIBC_PREREQ
+#if __GLIBC_PREREQ(2, 7)
+          "e" // glibc extension to enable O_CLOEXEC
+#endif
+#endif
+          );
    }
    if (f == nullptr) {
      result->reset();
@@ -201,7 +201,7 @@ class MockSequentialFile : public SequentialFile {
    if (n > available) {
      n = available;
    }
-    pos_ += n;
+    pos_ += static_cast<size_t>(n);
    return Status::OK();
  }

@@ -165,7 +165,6 @@ class PosixLogger : public Logger {

      size_t sz = fwrite(base, 1, write_size, file_);
      flush_pending_ = true;
-      assert(sz == write_size);
      if (sz > 0) {
        log_size_ += write_size;
      }
@@ -42,9 +42,6 @@
  (5) All of the pointer arguments must be non-NULL.
 */

-#ifndef STORAGE_ROCKSDB_INCLUDE_C_H_
-#define STORAGE_ROCKSDB_INCLUDE_C_H_
-
 #pragma once

 #ifdef _WIN32
@@ -126,6 +123,8 @@ typedef struct rocksdb_transaction_t rocksdb_transaction_t;
 typedef struct rocksdb_checkpoint_t rocksdb_checkpoint_t;
 typedef struct rocksdb_wal_iterator_t rocksdb_wal_iterator_t;
 typedef struct rocksdb_wal_readoptions_t rocksdb_wal_readoptions_t;
+typedef struct rocksdb_memory_consumers_t rocksdb_memory_consumers_t;
+typedef struct rocksdb_memory_usage_t rocksdb_memory_usage_t;

 /* DB operations */

@@ -1675,8 +1674,33 @@ extern ROCKSDB_LIBRARY_API void rocksdb_pinnableslice_destroy(
 extern ROCKSDB_LIBRARY_API const char* rocksdb_pinnableslice_value(
    const rocksdb_pinnableslice_t* t, size_t* vlen);

+extern ROCKSDB_LIBRARY_API rocksdb_memory_consumers_t*
+    rocksdb_memory_consumers_create();
+extern ROCKSDB_LIBRARY_API void rocksdb_memory_consumers_add_db(
+    rocksdb_memory_consumers_t* consumers, rocksdb_t* db);
+extern ROCKSDB_LIBRARY_API void rocksdb_memory_consumers_add_cache(
+    rocksdb_memory_consumers_t* consumers, rocksdb_cache_t* cache);
+extern ROCKSDB_LIBRARY_API void rocksdb_memory_consumers_destroy(
+    rocksdb_memory_consumers_t* consumers);
+extern ROCKSDB_LIBRARY_API rocksdb_memory_usage_t*
+rocksdb_approximate_memory_usage_create(rocksdb_memory_consumers_t* consumers,
+                                       char** errptr);
+extern ROCKSDB_LIBRARY_API void rocksdb_approximate_memory_usage_destroy(
+    rocksdb_memory_usage_t* usage);
+
+extern ROCKSDB_LIBRARY_API uint64_t
+rocksdb_approximate_memory_usage_get_mem_table_total(
+    rocksdb_memory_usage_t* memory_usage);
+extern ROCKSDB_LIBRARY_API uint64_t
+rocksdb_approximate_memory_usage_get_mem_table_unflushed(
+    rocksdb_memory_usage_t* memory_usage);
+extern ROCKSDB_LIBRARY_API uint64_t
+rocksdb_approximate_memory_usage_get_mem_table_readers_total(
+    rocksdb_memory_usage_t* memory_usage);
+extern ROCKSDB_LIBRARY_API uint64_t
+rocksdb_approximate_memory_usage_get_cache_total(
+    rocksdb_memory_usage_t* memory_usage);
+
 #ifdef __cplusplus
 }  /* end extern "C" */
 #endif
-
-#endif  /* STORAGE_ROCKSDB_INCLUDE_C_H_ */
@@ -16,8 +16,7 @@
 // non-const method, all threads accessing the same Iterator must use
 // external synchronization.

-#ifndef INCLUDE_ROCKSDB_CLEANABLE_H_
-#define INCLUDE_ROCKSDB_CLEANABLE_H_
+#pragma once

 namespace rocksdb {

@@ -78,5 +77,3 @@ class Cleanable {
 };

 }  // namespace rocksdb
-
-#endif  // INCLUDE_ROCKSDB_CLEANABLE_H_
@@ -6,8 +6,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

-#ifndef STORAGE_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
-#define STORAGE_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
+#pragma once

 #include <cassert>
 #include <memory>
@@ -206,5 +205,3 @@ class CompactionFilterFactory {
 };

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_COMPACTION_FILTER_H_
@@ -6,8 +6,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

-#ifndef STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_
-#define STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_
+#pragma once

 #include <string>

@@ -92,5 +91,3 @@ extern const Comparator* BytewiseComparator();
 extern const Comparator* ReverseBytewiseComparator();

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_COMPARATOR_H_
@@ -6,8 +6,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

-#ifndef STORAGE_ROCKSDB_INCLUDE_DB_H_
-#define STORAGE_ROCKSDB_INCLUDE_DB_H_
+#pragma once

 #include <stdint.h>
 #include <stdio.h>
@@ -950,14 +949,14 @@ class DB {
  // GetLiveFiles followed by GetSortedWalFiles can generate a lossless backup

  // Retrieve the list of all files in the database. The files are
-  // relative to the dbname and are not absolute paths. The valid size of the
-  // manifest file is returned in manifest_file_size. The manifest file is an
-  // ever growing file, but only the portion specified by manifest_file_size is
-  // valid for this snapshot.
-  // Setting flush_memtable to true does Flush before recording the live files.
-  // Setting flush_memtable to false is useful when we don't want to wait for
-  // flush which may have to wait for compaction to complete taking an
-  // indeterminate time.
+  // relative to the dbname and are not absolute paths. Despite being relative
+  // paths, the file names begin with "/". The valid size of the manifest file
+  // is returned in manifest_file_size. The manifest file is an ever growing
+  // file, but only the portion specified by manifest_file_size is valid for
+  // this snapshot. Setting flush_memtable to true does Flush before recording
+  // the live files. Setting flush_memtable to false is useful when we don't
+  // want to wait for flush which may have to wait for compaction to complete
+  // taking an indeterminate time.
  //
  // In case you have multiple column families, even if flush_memtable is true,
  // you still need to call GetSortedWalFiles after GetLiveFiles to compensate
@@ -1221,5 +1220,3 @@ Status RepairDB(const std::string& dbname, const Options& options);
 #endif

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_DB_H_
@@ -14,8 +14,7 @@
 // All Env implementations are safe for concurrent access from
 // multiple threads without any external synchronization.

-#ifndef STORAGE_ROCKSDB_INCLUDE_ENV_H_
-#define STORAGE_ROCKSDB_INCLUDE_ENV_H_
+#pragma once

 #include <stdint.h>
 #include <cstdarg>
@@ -478,6 +477,15 @@ class Env {
  // Returns the ID of the current thread.
  virtual uint64_t GetThreadID() const;

+// This seems to clash with a macro on Windows, so #undef it here
+#undef GetFreeSpace
+
+  // Get the amount of free disk space
+  virtual Status GetFreeSpace(const std::string& /*path*/,
+                              uint64_t* /*diskfree*/) {
+    return Status::NotSupported();
+  }
+
 protected:
  // The pointer to an internal structure that will update the
  // status of each thread.
@@ -1267,5 +1275,3 @@ Status NewHdfsEnv(Env** hdfs_env, const std::string& fsname);
 Env* NewTimedEnv(Env* base_env);

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_ENV_H_
@@ -17,8 +17,7 @@
 // Most people will want to use the builtin bloom filter support (see
 // NewBloomFilterPolicy() below).

-#ifndef STORAGE_ROCKSDB_INCLUDE_FILTER_POLICY_H_
-#define STORAGE_ROCKSDB_INCLUDE_FILTER_POLICY_H_
+#pragma once

 #include <memory>
 #include <stdexcept>
@@ -149,5 +148,3 @@ class FilterPolicy {
 extern const FilterPolicy* NewBloomFilterPolicy(int bits_per_key,
    bool use_block_based_builder = true);
 }
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_FILTER_POLICY_H_
@@ -16,8 +16,7 @@
 // non-const method, all threads accessing the same Iterator must use
 // external synchronization.

-#ifndef STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
-#define STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
+#pragma once

 #include <string>
 #include "rocksdb/cleanable.h"
@@ -119,5 +118,3 @@ extern Iterator* NewEmptyIterator();
 extern Iterator* NewErrorIterator(const Status& status);

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_ITERATOR_H_
@@ -2,8 +2,8 @@
 //  This source code is licensed under both the GPLv2 (found in the
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).
-#ifndef ROCKSDB_LITE
 #pragma once
+#ifndef ROCKSDB_LITE
 #include <string>
 #include <vector>
 #include "rocksdb/db.h"
@@ -27,6 +27,7 @@ enum class TableFileCreationReason {
  kFlush,
  kCompaction,
  kRecovery,
+  kMisc,
 };

 struct TableFileCreationBriefInfo {
@@ -103,6 +104,7 @@ enum class FlushReason : int {
  kDeleteFiles = 0x08,
  kAutoCompaction = 0x09,
  kManualFlush = 0x0a,
+  kErrorRecovery = 0xb,
 };

 enum class BackgroundErrorReason {
@@ -393,6 +395,21 @@ class EventListener {
  // returns.  Otherwise, RocksDB may be blocked.
  virtual void OnStallConditionsChanged(const WriteStallInfo& /*info*/) {}

+  // A callback function for RocksDB which will be called just before
+  // starting the automatic recovery process for recoverable background
+  // errors, such as NoSpace(). The callback can suppress the automatic
+  // recovery by setting *auto_recovery to false. The database will then
+  // have to be transitioned out of read-only mode by calling DB::Resume()
+  virtual void OnErrorRecoveryBegin(BackgroundErrorReason /* reason */,
+                                    Status /* bg_error */,
+                                    bool* /* auto_recovery */) {}
+
+  // A callback function for RocksDB which will be called once the database
+  // is recovered from read-only mode after an error. When this is called, it
+  // means normal writes to the database can be issued and the user can
+  // initiate any further recovery actions needed
+  virtual void OnErrorRecoveryCompleted(Status /* old_bg_error */) {}
+
  virtual ~EventListener() {}
 };

@@ -144,6 +144,14 @@ class MemTableRep {
  // or any writes done directly to entries accessed through the iterator.)
  virtual void MarkReadOnly() { }

+  // Notify this table rep that it has been flushed to stable storage.
+  // By default, does nothing.
+  //
+  // Invariant: MarkReadOnly() is called, before MarkFlushed().
+  // Note that this method if overridden, should not run for an extended period
+  // of time. Otherwise, RocksDB may be blocked.
+  virtual void MarkFlushed() { }
+
  // Look up key from the mem table, since the first key in the mem table whose
  // user_key matches the one given k, call the function callback_func(), with
  // callback_args directly forwarded as the first parameter, and the mem table
@@ -3,8 +3,7 @@
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).

-#ifndef STORAGE_ROCKSDB_INCLUDE_MERGE_OPERATOR_H_
-#define STORAGE_ROCKSDB_INCLUDE_MERGE_OPERATOR_H_
+#pragma once

 #include <deque>
 #include <memory>
@@ -241,5 +240,3 @@ class AssociativeMergeOperator : public MergeOperator {
 };

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_MERGE_OPERATOR_H_
@@ -65,7 +65,7 @@ struct SstFileMetaData {
        num_reads_sampled(0),
        being_compacted(false) {}
  SstFileMetaData(const std::string& _file_name, const std::string& _path,
-                  uint64_t _size, SequenceNumber _smallest_seqno,
+                  size_t _size, SequenceNumber _smallest_seqno,
                  SequenceNumber _largest_seqno,
                  const std::string& _smallestkey,
                  const std::string& _largestkey, uint64_t _num_reads_sampled,
@@ -81,7 +81,7 @@ struct SstFileMetaData {
        being_compacted(_being_compacted) {}

  // File size in bytes.
-  uint64_t size;
+  size_t size;
  // The name of the file.
  std::string name;
  // The full path where the file locates.
@@ -6,8 +6,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.

-#ifndef STORAGE_ROCKSDB_INCLUDE_OPTIONS_H_
-#define STORAGE_ROCKSDB_INCLUDE_OPTIONS_H_
+#pragma once

 #include <stddef.h>
 #include <stdint.h>
@@ -1183,8 +1182,13 @@ struct FlushOptions {
  // If true, the flush will wait until the flush is done.
  // Default: true
  bool wait;
-
-  FlushOptions() : wait(true) {}
+  // If true, the flush would proceed immediately even it means writes will
+  // stall for the duration of the flush; if false the operation will wait
+  // until it's possible to do flush w/o causing stall or until required flush
+  // is performed by someone else (foreground call or background thread).
+  // Default: false
+  bool allow_write_stall;
+  FlushOptions() : wait(true), allow_write_stall(false) {}
 };

 // Create a Logger from provided DBOptions
@@ -1196,6 +1200,9 @@ extern Status CreateLoggerFromOptions(const std::string& dbname,
 struct CompactionOptions {
  // Compaction output compression type
  // Default: snappy
+  // If set to `kDisableCompressionOption`, RocksDB will choose compression type
+  // according to the `ColumnFamilyOptions`, taking into account the output
+  // level if `compression_per_level` is specified.
  CompressionType compression;
  // Compaction will create files of size `output_file_size_limit`.
  // Default: MAX, which means that compaction will create a single file
@@ -1284,5 +1291,3 @@ struct IngestExternalFileOptions {
 struct TraceOptions {};

 }  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_OPTIONS_H_
@@ -3,8 +3,7 @@
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).

-#ifndef STORAGE_ROCKSDB_INCLUDE_PERF_CONTEXT_H
-#define STORAGE_ROCKSDB_INCLUDE_PERF_CONTEXT_H
+#pragma once

 #include <stdint.h>
 #include <string>
@@ -176,5 +175,3 @@ struct PerfContext {
 PerfContext* get_perf_context();

 }
-
-#endif
@@ -3,8 +3,7 @@
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).

-#ifndef INCLUDE_ROCKSDB_PERF_LEVEL_H_
-#define INCLUDE_ROCKSDB_PERF_LEVEL_H_
+#pragma once

 #include <stdint.h>
 #include <string>
@@ -29,5 +28,3 @@ void SetPerfLevel(PerfLevel level);
 PerfLevel GetPerfLevel();

 }  // namespace rocksdb
-
-#endif  // INCLUDE_ROCKSDB_PERF_LEVEL_H_
@@ -16,8 +16,7 @@
 // non-const method, all threads accessing the same Slice must use
 // external synchronization.

-#ifndef STORAGE_ROCKSDB_INCLUDE_SLICE_H_
-#define STORAGE_ROCKSDB_INCLUDE_SLICE_H_
+#pragma once

 #include <assert.h>
 #include <cstdio>
@@ -48,7 +47,7 @@ class Slice {
 #ifdef __cpp_lib_string_view
  // Create a slice that refers to the same contents as "sv"
  /* implicit */
-  Slice(std::string_view sv) : data_(sv.data()), size_(sv.size()) { }
+  Slice(std::string_view sv) : data_(sv.data()), size_(sv.size()) {}
 #endif

  // Create a slice that refers to s[0,strlen(s)-1]
@@ -256,6 +255,4 @@ inline size_t Slice::difference_offset(const Slice& b) const {
  return off;
 }

-}  // namespace rocksdb
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_SLICE_H_
+}  // namespace rocksdb
@@ -12,8 +12,7 @@
 // define InDomain and InRange to determine which slices are in either
 // of these sets respectively.

-#ifndef STORAGE_ROCKSDB_INCLUDE_SLICE_TRANSFORM_H_
-#define STORAGE_ROCKSDB_INCLUDE_SLICE_TRANSFORM_H_
+#pragma once

 #include <string>

@@ -100,5 +99,3 @@ extern const SliceTransform* NewCappedPrefixTransform(size_t cap_len);
 extern const SliceTransform* NewNoopTransform();

 }
-
-#endif  // STORAGE_ROCKSDB_INCLUDE_SLICE_TRANSFORM_H_