using forked bg save causes more harm than good

change hasActiveChildProcess to return true only when there is an actual child process, add hasActiveChildProcessOrBGSave to catch case of forkless bgsave

README.md

@@ -141,9 +141,9 @@ To append a suffix to KeyDB program names, use:
 ***Note that the following dependencies may be needed: 
     % sudo apt-get install autoconf autotools-dev libnuma-dev libtool
 
-To buik=ld with TLS support, use:
+KeyDB by default is built with TLS enabled. To build without TLS support, use:
 
-    % make BUILD_TLS=yes
+    % make BUILD_TLS=no
 
 Running the tests with TLS enabled (you will need `tcl-tls`
 installed):

runtest-moduleapi

@@ -37,5 +37,6 @@ $TCLSH tests/test_helper.tcl \
 --single unit/moduleapi/hash \
 --single unit/moduleapi/zset \
 --single unit/moduleapi/stream \
+--single unit/moduleapi/load \
 --config server-threads 3 \
 "${@}"

src/Makefile

@@ -20,7 +20,7 @@ release_hdr := $(shell sh -c './mkreleasehdr.sh')
 uname_S := $(shell sh -c 'uname -s 2>/dev/null || echo not')
 uname_M := $(shell sh -c 'uname -m 2>/dev/null || echo not')
 OPTIMIZATION?=-O2 -flto
-DEPENDENCY_TARGETS=hiredis linenoise lua hdr_histogram rocksdb
+DEPENDENCY_TARGETS=hiredis linenoise lua hdr_histogram
 NODEPS:=clean distclean
 
 # Default settings
@@ -376,7 +376,7 @@ endif
 
 REDIS_SERVER_NAME=keydb-server$(PROG_SUFFIX)
 REDIS_SENTINEL_NAME=keydb-sentinel$(PROG_SUFFIX)
-REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o t_nhash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o acl.o storage.o rdb-s3.o fastlock.o new.o tracking.o cron.o connection.o tls.o sha256.o motd_server.o timeout.o setcpuaffinity.o AsyncWorkQueue.o snapshot.o storage/rocksdb.o storage/rocksdbfactory.o storage/teststorageprovider.o keydbutils.o StorageCache.o monotonic.o cli_common.o mt19937-64.o $(ASM_OBJ)
+REDIS_SERVER_OBJ=adlist.o quicklist.o ae.o anet.o dict.o server.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o t_nhash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crcspeed.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o latency.o sparkline.o redis-check-rdb.o redis-check-aof.o geo.o lazyfree.o module.o evict.o expire.o geohash.o geohash_helper.o childinfo.o defrag.o siphash.o rax.o t_stream.o listpack.o localtime.o acl.o storage.o rdb-s3.o fastlock.o new.o tracking.o cron.o connection.o tls.o sha256.o motd_server.o timeout.o setcpuaffinity.o AsyncWorkQueue.o snapshot.o storage/teststorageprovider.o keydbutils.o StorageCache.o monotonic.o cli_common.o mt19937-64.o $(ASM_OBJ) $(STORAGE_OBJ)
 KEYDB_SERVER_OBJ=SnapshotPayloadParseState.o
 REDIS_CLI_NAME=keydb-cli$(PROG_SUFFIX)
 REDIS_CLI_OBJ=anet.o adlist.o dict.o redis-cli.o redis-cli-cpphelper.o zmalloc.o release.o anet.o ae.o crcspeed.o crc64.o siphash.o crc16.o storage-lite.o fastlock.o motd_client.o monotonic.o cli_common.o mt19937-64.o $(ASM_OBJ)
@@ -437,7 +437,7 @@ endif
 
 # keydb-server
 $(REDIS_SERVER_NAME): $(REDIS_SERVER_OBJ) $(KEYDB_SERVER_OBJ)
-	$(REDIS_LD) -o $@ $^ ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a ../deps/rocksdb/librocksdb.a $(FINAL_LIBS)
+	$(REDIS_LD) -o $@ $^ ../deps/hiredis/libhiredis.a ../deps/lua/src/liblua.a $(FINAL_LIBS)
 
 # keydb-sentinel
 $(REDIS_SENTINEL_NAME): $(REDIS_SERVER_NAME)

src/ae.cpp

@@ -716,11 +716,6 @@ int aeProcessEvents(aeEventLoop *eventLoop, int flags)
             }
         }
 
-        if (eventLoop->flags & AE_DONT_WAIT) {
-            tv.tv_sec = tv.tv_usec = 0;
-            tvp = &tv;
-        }
-
         if (eventLoop->beforesleep != NULL && flags & AE_CALL_BEFORE_SLEEP) {
             std::unique_lock<decltype(g_lock)> ulock(g_lock, std::defer_lock);
             if (!(eventLoop->beforesleepFlags & AE_SLEEP_THREADSAFE)) {
@@ -731,6 +726,11 @@ int aeProcessEvents(aeEventLoop *eventLoop, int flags)
             eventLoop->beforesleep(eventLoop);
         }
 
+        if (eventLoop->flags & AE_DONT_WAIT) {
+            tv.tv_sec = tv.tv_usec = 0;
+            tvp = &tv;
+        }
+
         /* Call the multiplexing API, will return only on timeout or when
          * some event fires. */
         numevents = aeApiPoll(eventLoop, tvp);
@@ -859,6 +859,11 @@ void aeReleaseForkLock()
     g_forkLock.downgradeWrite();
 }
 
+void aeForkLockInChild()
+{
+    g_forkLock.setNotify(false);
+}
+
 int aeThreadOwnsLock()
 {
     return fOwnLockOverride || g_lock.fOwnLock();

src/ae.h

@@ -171,6 +171,7 @@ int aeTryAcquireLock(int fWeak);
 void aeThreadOffline();
 void aeReleaseLock();
 void aeReleaseForkLock();
+void aeForkLockInChild();
 int aeThreadOwnsLock();
 void aeSetThreadOwnsLockOverride(int fOverride);
 int aeLockContested(int threshold);

src/aof.cpp

@@ -285,7 +285,7 @@ int startAppendOnly(void) {
             strerror(errno));
         return C_ERR;
     }
-    if (hasActiveChildProcess() && g_pserver->child_type != CHILD_TYPE_AOF) {
+    if (hasActiveChildProcessOrBGSave() && g_pserver->child_type != CHILD_TYPE_AOF) {
         g_pserver->aof_rewrite_scheduled = 1;
         serverLog(LL_WARNING,"AOF was enabled but there is already another background operation. An AOF background was scheduled to start when possible.");
     } else {
@@ -438,7 +438,7 @@ void flushAppendOnlyFile(int force) {
      * useful for graphing / monitoring purposes. */
     if (sync_in_progress) {
         latencyAddSampleIfNeeded("aof-write-pending-fsync",latency);
-    } else if (hasActiveChildProcess()) {
+    } else if (hasActiveChildProcessOrBGSave()) {
         latencyAddSampleIfNeeded("aof-write-active-child",latency);
     } else {
         latencyAddSampleIfNeeded("aof-write-alone",latency);
@@ -535,7 +535,7 @@ void flushAppendOnlyFile(int force) {
 try_fsync:
     /* Don't fsync if no-appendfsync-on-rewrite is set to yes and there are
      * children doing I/O in the background. */
-    if (g_pserver->aof_no_fsync_on_rewrite && hasActiveChildProcess())
+    if (g_pserver->aof_no_fsync_on_rewrite && hasActiveChildProcessOrBGSave())
         return;
 
     /* Perform the fsync if needed. */
@@ -752,7 +752,7 @@ void feedAppendOnlyFile(struct redisCommand *cmd, int dictid, robj **argv, int a
      * accumulate the differences between the child DB and the current one
      * in a buffer, so that when the child process will do its work we
      * can append the differences to the new append only file. */
-    if (g_pserver->child_type == CHILD_TYPE_AOF)
+    if (hasActiveChildProcess() && g_pserver->child_type == CHILD_TYPE_AOF)
         aofRewriteBufferAppend((unsigned char*)buf,sdslen(buf));
 
     sdsfree(buf);
@@ -1887,7 +1887,7 @@ void aofClosePipes(void) {
 int rewriteAppendOnlyFileBackground(void) {
     pid_t childpid;
 
-    if (hasActiveChildProcess()) return C_ERR;
+    if (hasActiveChildProcessOrBGSave()) return C_ERR;
     if (aofCreatePipes() != C_OK) return C_ERR;
     if ((childpid = redisFork(CHILD_TYPE_AOF)) == 0) {
         char tmpfile[256];
@@ -1930,7 +1930,7 @@ int rewriteAppendOnlyFileBackground(void) {
 void bgrewriteaofCommand(client *c) {
     if (g_pserver->child_type == CHILD_TYPE_AOF) {
         addReplyError(c,"Background append only file rewriting already in progress");
-    } else if (hasActiveChildProcess()) {
+    } else if (hasActiveChildProcessOrBGSave()) {
         g_pserver->aof_rewrite_scheduled = 1;
         addReplyStatus(c,"Background append only file rewriting scheduled");
     } else if (rewriteAppendOnlyFileBackground() == C_OK) {

src/bitops.cpp

@@ -322,7 +322,7 @@ handle_wrap:
     return 1;
 }
 
-int checkSignedBitfieldOverflow(int64_t value, int64_t incr, uint64_t bits, int owtype, int64_t *limit) {
+int checkSignedBitfieldOverflow(int64_t value, int64_t incr, int bits, int owtype, int64_t *limit) {
     int64_t max = (bits == 64) ? INT64_MAX : (((int64_t)1<<(bits-1))-1);
     int64_t min = (-max)-1;
 

src/config.cpp

@@ -40,6 +40,7 @@
 #endif
 
 const char *KEYDB_SET_VERSION = KEYDB_REAL_VERSION;
+size_t g_semiOrderedSetTargetBucketSize = 0;    // Its a header only class so nowhere else for this to go
 
 /*-----------------------------------------------------------------------------
  * Config file name-value maps.
@@ -2910,6 +2911,7 @@ standardConfig configs[] = {
     createBoolConfig("allow-write-during-load", NULL, MODIFIABLE_CONFIG, g_pserver->fWriteDuringActiveLoad, 0, NULL, NULL),
     createBoolConfig("force-backlog-disk-reserve", NULL, MODIFIABLE_CONFIG, cserver.force_backlog_disk, 0, NULL, NULL),
     createBoolConfig("soft-shutdown", NULL, MODIFIABLE_CONFIG, g_pserver->config_soft_shutdown, 0, NULL, NULL),
+    createSizeTConfig("semi-ordered-set-bucket-size", NULL, MODIFIABLE_CONFIG, 0, 1024, g_semiOrderedSetTargetBucketSize, 0, INTEGER_CONFIG, NULL, NULL),
 
 #ifdef USE_OPENSSL
     createIntConfig("tls-port", NULL, MODIFIABLE_CONFIG, 0, 65535, g_pserver->tls_port, 0, INTEGER_CONFIG, NULL, updateTLSPort), /* TCP port. */

src/db.cpp

@@ -93,7 +93,7 @@ static void lookupKeyUpdateObj(robj *val, int flags)
     /* Update the access time for the ageing algorithm.
      * Don't do it if we have a saving child, as this will trigger
      * a copy on write madness. */
-    if (!hasActiveChildProcess() && !(flags & LOOKUP_NOTOUCH))
+    if (!hasActiveChildProcessOrBGSave() && !(flags & LOOKUP_NOTOUCH))
     {
         if (g_pserver->maxmemory_policy & MAXMEMORY_FLAG_LFU) {
             updateLFU(val);
@@ -2607,6 +2607,14 @@ void clusterStorageLoadCallback(const char *rgchkey, size_t cch, void *)
     slotToKeyUpdateKeyCore(rgchkey, cch, true /*add*/);
 }
 
+void moduleLoadCallback(const char * rgchKey, size_t cchKey, void *data) {
+    if (g_pserver->cluster_enabled) {
+        clusterStorageLoadCallback(rgchKey, cchKey, data);
+    }
+    robj *keyobj = createEmbeddedStringObject(rgchKey, cchKey);
+    moduleNotifyKeyspaceEvent(NOTIFY_LOADED, "loaded", keyobj, *(int *)data);
+}
+
 void redisDb::initialize(int id)
 {
     redisDbPersistentData::initialize();
@@ -2625,8 +2633,8 @@ void redisDb::storageProviderInitialize()
 {
     if (g_pserver->m_pstorageFactory != nullptr)
     {
-        IStorageFactory::key_load_iterator itr = (g_pserver->cluster_enabled) ? clusterStorageLoadCallback : nullptr;
-        this->setStorageProvider(StorageCache::create(g_pserver->m_pstorageFactory, id, itr, nullptr));
+        IStorageFactory::key_load_iterator itr = moduleLoadCallback;
+        this->setStorageProvider(StorageCache::create(g_pserver->m_pstorageFactory, id, itr, &id));
     }
 }
 

src/rdb.cpp

@@ -1679,17 +1679,15 @@ int rdbSaveBackground(rdbSaveInfo *rsi) {
     pthread_t child;
     long long start;
 
-    if (hasActiveChildProcess()) return C_ERR;
+    if (hasActiveChildProcessOrBGSave()) return C_ERR;
 
     g_pserver->dirty_before_bgsave = g_pserver->dirty;
     g_pserver->lastbgsave_try = time(NULL);
     openChildInfoPipe();
 
     start = ustime();
+    latencyStartMonitor(g_pserver->rdb_save_latency);
 
-    
-    g_pserver->stat_fork_time = ustime()-start;
-    g_pserver->stat_fork_rate = (double) zmalloc_used_memory() * 1000000 / g_pserver->stat_fork_time / (1024*1024*1024); /* GB per second. */
     if (launchRdbSaveThread(child, rsi) != C_OK) {
         closeChildInfoPipe();
         g_pserver->lastbgsave_status = C_ERR;
@@ -1697,6 +1695,9 @@ int rdbSaveBackground(rdbSaveInfo *rsi) {
             strerror(errno));
         return C_ERR;
     }
+
+    g_pserver->stat_fork_time = ustime()-start;
+    g_pserver->stat_fork_rate = (double) zmalloc_used_memory() * 1000000 / g_pserver->stat_fork_time / (1024*1024*1024); /* GB per second. */
     latencyAddSampleIfNeeded("fork",g_pserver->stat_fork_time/1000);
     serverLog(LL_NOTICE,"Background saving started");
     g_pserver->rdb_save_time_start = time(NULL);
@@ -3601,6 +3602,8 @@ static void backgroundSaveDoneHandlerDisk(int exitcode, bool fCancelled) {
         g_pserver->dirty = g_pserver->dirty - g_pserver->dirty_before_bgsave;
         g_pserver->lastsave = time(NULL);
         g_pserver->lastbgsave_status = C_OK;
+        latencyEndMonitor(g_pserver->rdb_save_latency);
+        latencyAddSampleIfNeeded("rdb-save",g_pserver->rdb_save_latency);
     } else if (!fCancelled && exitcode != 0) {
         serverLog(LL_WARNING, "Background saving error");
         g_pserver->lastbgsave_status = C_ERR;
@@ -3691,7 +3694,7 @@ void killRDBChild(bool fSynchronous) {
     serverAssert(GlobalLocksAcquired());
 
     if (cserver.fForkBgSave) {
-        kill(g_pserver->rdb_child_pid,SIGUSR1);
+        kill(g_pserver->child_pid,SIGUSR1);
     } else { 
         g_pserver->rdbThreadVars.fRdbThreadCancel = true;
         if (g_pserver->rdb_child_type == RDB_CHILD_TYPE_SOCKET) {
@@ -3782,7 +3785,7 @@ int rdbSaveToSlavesSockets(rdbSaveInfo *rsi) {
     int pipefds[2];
     rdbSaveSocketThreadArgs *args = nullptr;
 
-    if (hasActiveChildProcess()) return C_ERR;
+    if (hasActiveChildProcessOrBGSave()) return C_ERR;
 
     /* Even if the previous fork child exited, don't start a new one until we
      * drained the pipe. */

src/readwritelock.h

@@ -8,6 +8,7 @@ class readWriteLock {
     int m_readCount = 0;
     int m_writeCount = 0;
     bool m_writeWaiting = false;
+    bool m_notify = true;
 public:
     readWriteLock(const char *name) : m_readLock(name), m_writeLock(name) {}
 
@@ -65,7 +66,8 @@ public:
     void releaseRead() {
         std::unique_lock<fastlock> rm(m_readLock);
         m_readCount--;
-        m_cv.notify_all();
+        if (m_notify)
+            m_cv.notify_all();
     }
 
     void releaseWrite(bool exclusive = true) {
@@ -74,7 +76,8 @@ public:
         if (exclusive)
             m_writeLock.unlock();
         m_writeCount--;
-        m_cv.notify_all();
+        if (m_notify)
+            m_cv.notify_all();
     }
 
     void downgradeWrite(bool exclusive = true) {
@@ -82,6 +85,10 @@ public:
         acquireRead();
     }
 
+    void setNotify(bool notify) {
+        m_notify = notify;
+    }
+
     bool hasReader() {
         return m_readCount > 0;
     }

src/redismodule.h

@@ -326,6 +326,7 @@ static const RedisModuleEvent
 #define REDISMODULE_SUBEVENT_LOADING_ENDED 3
 #define REDISMODULE_SUBEVENT_LOADING_FAILED 4
 #define _REDISMODULE_SUBEVENT_LOADING_NEXT 5
+#define REDISMODULE_SUBEVENT_LOADING_FLASH_START 6
 
 #define REDISMODULE_SUBEVENT_CLIENT_CHANGE_CONNECTED 0
 #define REDISMODULE_SUBEVENT_CLIENT_CHANGE_DISCONNECTED 1

src/replication.cpp

@@ -1538,7 +1538,7 @@ void syncCommand(client *c) {
         } else {
             /* We don't have a BGSAVE in progress, let's start one. Diskless
              * or disk-based mode is determined by replica's capacity. */
-            if (!hasActiveChildProcess()) {
+            if (!hasActiveChildProcessOrBGSave()) {
                 startBgsaveForReplication(c->slave_capa);
             } else {
                 serverLog(LL_NOTICE,
@@ -4984,7 +4984,7 @@ void replicationStartPendingFork(void) {
      * In case of diskless replication, we make sure to wait the specified
      * number of seconds (according to configuration) so that other slaves
      * have the time to arrive before we start streaming. */
-    if (!hasActiveChildProcess()) {
+    if (!hasActiveChildProcessOrBGSave()) {
         time_t idle, max_idle = 0;
         int slaves_waiting = 0;
         int mincapa = -1;

src/semiorderedset.h

@@ -27,6 +27,7 @@ namespace keydbutils
     template<>
     size_t hash(const sdsview &);
 }
+extern size_t g_semiOrderedSetTargetBucketSize;
 
 template<typename T, typename T_KEY = T, bool MEMMOVE_SAFE = false>
 class semiorderedset
@@ -41,11 +42,14 @@ class semiorderedset
     size_t idxRehash = (1ULL << bits_min); 
     int cfPauseRehash = 0;
 
-    constexpr size_t targetElementsPerBucket()
+    inline size_t targetElementsPerBucket()
     {
         // Aim for roughly 4 cache lines per bucket (determined by imperical testing)
         //  lower values are faster but use more memory
-        return std::max((64/sizeof(T))*8, (size_t)2);
+        if (g_semiOrderedSetTargetBucketSize == 0)
+            return std::max((64/sizeof(T))*8, (size_t)2);
+        else
+            return g_semiOrderedSetTargetBucketSize;
     }
 
 public:

src/server.cpp

@@ -1706,7 +1706,7 @@ int redisDbPersistentData::incrementallyRehash() {
  * for dict.c to resize the hash tables accordingly to the fact we have an
  * active fork child running. */
 void updateDictResizePolicy(void) {
-    if (!hasActiveChildProcess() || (g_pserver->FRdbSaveInProgress() && !cserver.fForkBgSave))
+    if (!hasActiveChildProcess())
         dictEnableResize();
     else
         dictDisableResize();
@@ -1725,7 +1725,11 @@ const char *strChildType(int type) {
 /* Return true if there are active children processes doing RDB saving,
  * AOF rewriting, or some side process spawned by a loaded module. */
 int hasActiveChildProcess() {
-    return g_pserver->FRdbSaveInProgress() || g_pserver->child_pid != -1;
+    return g_pserver->child_pid != -1;
+}
+
+int hasActiveChildProcessOrBGSave() {
+    return g_pserver->FRdbSaveInProgress() || hasActiveChildProcess();
 }
 
 void resetChildState() {
@@ -2074,7 +2078,7 @@ void databasesCron(bool fMainThread) {
     /* Perform hash tables rehashing if needed, but only if there are no
      * other processes saving the DB on disk. Otherwise rehashing is bad
      * as will cause a lot of copy-on-write of memory pages. */
-    if (!hasActiveChildProcess() || g_pserver->FRdbSaveInProgress()) {
+    if (!hasActiveChildProcess()) {
         /* We use global counters so if we stop the computation at a given
          * DB we'll be able to start from the successive in the next
          * cron loop iteration. */
@@ -2468,14 +2472,14 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
 
     /* Start a scheduled AOF rewrite if this was requested by the user while
      * a BGSAVE was in progress. */
-    if (!hasActiveChildProcess() &&
+    if (!hasActiveChildProcessOrBGSave() &&
         g_pserver->aof_rewrite_scheduled)
     {
         rewriteAppendOnlyFileBackground();
     }
 
     /* Check if a background saving or AOF rewrite in progress terminated. */
-    if (hasActiveChildProcess() || ldbPendingChildren())
+    if (hasActiveChildProcessOrBGSave() || ldbPendingChildren())
     {
         run_with_period(1000) receiveChildInfo();
         checkChildrenDone();
@@ -2517,7 +2521,7 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
 
         /* Trigger an AOF rewrite if needed. */
         if (g_pserver->aof_state == AOF_ON &&
-            !hasActiveChildProcess() &&
+            !hasActiveChildProcessOrBGSave() &&
             g_pserver->aof_rewrite_perc &&
             g_pserver->aof_current_size > g_pserver->aof_rewrite_min_size)
         {
@@ -2601,7 +2605,7 @@ int serverCron(struct aeEventLoop *eventLoop, long long id, void *clientData) {
      * Note: this code must be after the replicationCron() call above so
      * make sure when refactoring this file to keep this order. This is useful
      * because we want to give priority to RDB savings for replication. */
-    if (!hasActiveChildProcess() &&
+    if (!hasActiveChildProcessOrBGSave() &&
         g_pserver->rdb_bgsave_scheduled &&
         (g_pserver->unixtime-g_pserver->lastbgsave_try > CONFIG_BGSAVE_RETRY_DELAY ||
          g_pserver->lastbgsave_status == C_OK))
@@ -2815,9 +2819,6 @@ void beforeSleep(struct aeEventLoop *eventLoop) {
 
     runAndPropogateToReplicas(processClients);
 
-    /* Handle precise timeouts of blocked clients. */
-    handleBlockedClientsTimeout();
-
     /* Just call a subset of vital functions in case we are re-entering
      * the event loop from processEventsWhileBlocked(). Note that in this
      * case we keep track of the number of events we are processing, since
@@ -4067,12 +4068,6 @@ void initServer(void) {
         }
     }
 
-    /* We have to initialize storage providers after the cluster has been initialized */
-    for (int idb = 0; idb < cserver.dbnum; ++idb)
-    {
-        g_pserver->db[idb]->storageProviderInitialize();
-    }
-
     saveMasterStatusToStorage(false); // eliminate the repl-offset field
     
     /* Initialize ACL default password if it exists */
@@ -4085,6 +4080,15 @@ void initServer(void) {
  * Thread Local Storage initialization collides with dlopen call.
  * see: https://sourceware.org/bugzilla/show_bug.cgi?id=19329 */
 void InitServerLast() {
+
+    /* We have to initialize storage providers after the cluster has been initialized */
+    moduleFireServerEvent(REDISMODULE_EVENT_LOADING, REDISMODULE_SUBEVENT_LOADING_FLASH_START, NULL);
+    for (int idb = 0; idb < cserver.dbnum; ++idb)
+    {
+        g_pserver->db[idb]->storageProviderInitialize();
+    }
+    moduleFireServerEvent(REDISMODULE_EVENT_LOADING, REDISMODULE_SUBEVENT_LOADING_ENDED, NULL);
+
     bioInit();
     set_jemalloc_bg_thread(cserver.jemalloc_bg_thread);
     g_pserver->initial_memory_usage = zmalloc_used_memory();
@@ -6884,6 +6888,7 @@ int redisFork(int purpose) {
     latencyAddSampleIfNeeded("fork-lock",(ustime()-startWriteLock)/1000);
     if ((childpid = fork()) == 0) {
         /* Child */
+        aeForkLockInChild();
         aeReleaseForkLock();
         g_pserver->in_fork_child = purpose;
         setOOMScoreAdj(CONFIG_OOM_BGCHILD);
@@ -7566,6 +7571,29 @@ int main(int argc, char **argv) {
 
     validateConfiguration();
 
+    if (!g_pserver->sentinel_mode) {
+    #ifdef __linux__
+        linuxMemoryWarnings();
+    #if defined (__arm64__)
+        int ret;
+        if ((ret = linuxMadvFreeForkBugCheck())) {
+            if (ret == 1)
+                serverLog(LL_WARNING,"WARNING Your kernel has a bug that could lead to data corruption during background save. "
+                                        "Please upgrade to the latest stable kernel.");
+            else
+                serverLog(LL_WARNING, "Failed to test the kernel for a bug that could lead to data corruption during background save. "
+                                        "Your system could be affected, please report this error.");
+            if (!checkIgnoreWarning("ARM64-COW-BUG")) {
+                serverLog(LL_WARNING,"KeyDB will now exit to prevent data corruption. "
+                                        "Note that it is possible to suppress this warning by setting the following config: ignore-warnings ARM64-COW-BUG");
+                exit(1);
+            }
+        }
+    #endif /* __arm64__ */
+    #endif /* __linux__ */
+    }
+
+
     const char *err;
     if (!initializeStorageProvider(&err))
     {
@@ -7591,25 +7619,6 @@ int main(int argc, char **argv) {
     if (!g_pserver->sentinel_mode) {
         /* Things not needed when running in Sentinel mode. */
         serverLog(LL_WARNING,"Server initialized");
-    #ifdef __linux__
-        linuxMemoryWarnings();
-    #if defined (__arm64__)
-        int ret;
-        if ((ret = linuxMadvFreeForkBugCheck())) {
-            if (ret == 1)
-                serverLog(LL_WARNING,"WARNING Your kernel has a bug that could lead to data corruption during background save. "
-                                     "Please upgrade to the latest stable kernel.");
-            else
-                serverLog(LL_WARNING, "Failed to test the kernel for a bug that could lead to data corruption during background save. "
-                                      "Your system could be affected, please report this error.");
-            if (!checkIgnoreWarning("ARM64-COW-BUG")) {
-                serverLog(LL_WARNING,"KeyDB will now exit to prevent data corruption. "
-                                     "Note that it is possible to suppress this warning by setting the following config: ignore-warnings ARM64-COW-BUG");
-                exit(1);
-            }
-        }
-    #endif /* __arm64__ */
-    #endif /* __linux__ */
         moduleInitModulesSystemLast();
         moduleLoadFromQueue();
         ACLLoadUsersAtStartup();

src/server.h

@@ -2470,7 +2470,8 @@ struct redisServer {
     time_t lastbgsave_try;          /* Unix time of last attempted bgsave */
     time_t rdb_save_time_last;      /* Time used by last RDB save run. */
     time_t rdb_save_time_start;     /* Current RDB save start time. */
-    pid_t rdb_child_pid = -1;            /* Used only during fork bgsave */
+    mstime_t rdb_save_latency;      /* Used to track end to end latency of rdb save*/
+    pid_t rdb_child_pid = -1;       /* Used only during fork bgsave */
     int rdb_bgsave_scheduled;       /* BGSAVE when possible if true. */
     int rdb_child_type;             /* Type of save by active child. */
     int lastbgsave_status;          /* C_OK or C_ERR */
@@ -3254,6 +3255,7 @@ void receiveChildInfo(void);
 void executeWithoutGlobalLock(std::function<void()> func);
 int redisFork(int type);
 int hasActiveChildProcess();
+int hasActiveChildProcessOrBGSave();
 void resetChildState();
 int isMutuallyExclusiveChildType(int type);
 

tests/modules/Makefile

@@ -39,7 +39,8 @@ TEST_MODULES = \
     defragtest.so \
     hash.so \
     zset.so \
-    stream.so
+    stream.so \
+    load.so
 
 
 .PHONY: all

tests/modules/hooks.c

@@ -212,6 +212,7 @@ void loadingCallback(RedisModuleCtx *ctx, RedisModuleEvent e, uint64_t sub, void
         case REDISMODULE_SUBEVENT_LOADING_RDB_START: keyname = "loading-rdb-start"; break;
         case REDISMODULE_SUBEVENT_LOADING_AOF_START: keyname = "loading-aof-start"; break;
         case REDISMODULE_SUBEVENT_LOADING_REPL_START: keyname = "loading-repl-start"; break;
+        case REDISMODULE_SUBEVENT_LOADING_FLASH_START: keyname = "loading-flash-start"; break;
         case REDISMODULE_SUBEVENT_LOADING_ENDED: keyname = "loading-end"; break;
         case REDISMODULE_SUBEVENT_LOADING_FAILED: keyname = "loading-failed"; break;
     }

tests/modules/load.c

@@ -0,0 +1,94 @@
+/* Server hooks API example
+ *
+ * -----------------------------------------------------------------------------
+ *
+ * Copyright (c) 2019, Salvatore Sanfilippo <antirez at gmail dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *   * Neither the name of Redis nor the names of its contributors may be used
+ *     to endorse or promote products derived from this software without
+ *     specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#define REDISMODULE_EXPERIMENTAL_API
+#include "redismodule.h"
+
+size_t count, finalCount;
+
+/* Client state change callback. */
+void loadCallback(RedisModuleCtx *ctx, RedisModuleEvent e, uint64_t sub, void *data) {
+    REDISMODULE_NOT_USED(ctx);
+    REDISMODULE_NOT_USED(e);
+    REDISMODULE_NOT_USED(data);
+
+    if (sub == REDISMODULE_SUBEVENT_LOADING_FLASH_START || sub == REDISMODULE_SUBEVENT_LOADING_RDB_START || sub == REDISMODULE_SUBEVENT_LOADING_AOF_START || sub == REDISMODULE_SUBEVENT_LOADING_REPL_START) {
+        count = 0;
+        finalCount = 0;
+    } else if (sub == REDISMODULE_SUBEVENT_LOADING_ENDED) {
+        finalCount = count;
+    }
+}
+
+int loadKeyCallback(RedisModuleCtx *ctx, int type,  const char *event, RedisModuleString *key) {
+    REDISMODULE_NOT_USED(ctx);
+    REDISMODULE_NOT_USED(type);
+    REDISMODULE_NOT_USED(event);
+
+    const char *keyname = RedisModule_StringPtrLen(key, NULL);
+
+    RedisModule_Log(ctx, REDISMODULE_LOGLEVEL_NOTICE, "Loaded key: %s", keyname);
+
+    count++;
+    return 0;
+}
+
+int LoadCount_RedisCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    REDISMODULE_NOT_USED(argv);
+    RedisModule_AutoMemory(ctx); /* Use automatic memory management. */
+
+    if (argc != 1) return RedisModule_WrongArity(ctx);
+
+    RedisModule_ReplyWithLongLong(ctx, finalCount);
+
+    return REDISMODULE_OK;
+}
+
+/* This function must be present on each Redis module. It is used in order to
+ * register the commands into the Redis server. */
+int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    REDISMODULE_NOT_USED(argv);
+    REDISMODULE_NOT_USED(argc);
+
+    if (RedisModule_Init(ctx,"load",1,REDISMODULE_APIVER_1)
+        == REDISMODULE_ERR) return REDISMODULE_ERR;
+
+    RedisModule_SubscribeToServerEvent(ctx,
+        RedisModuleEvent_Loading, loadCallback);
+    RedisModule_SubscribeToKeyspaceEvents(ctx,
+        REDISMODULE_NOTIFY_LOADED, loadKeyCallback);
+
+    if (RedisModule_CreateCommand(ctx, "load.count",
+        LoadCount_RedisCommand,"readonly",1,1,1) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+    return REDISMODULE_OK;
+}

tests/unit/moduleapi/load.tcl

@@ -0,0 +1,15 @@
+set testmodule [file normalize tests/modules/load.so]
+
+if {$::flash_enabled} {
+    start_server [list tags [list "modules"] overrides [list storage-provider {flash ./rocks.db.master} databases 256 loadmodule $testmodule]] {
+        test "Module is notified of keys loaded from flash" {
+            r flushall
+            r set foo bar
+            r set bar foo
+            r set foobar barfoo
+            assert_equal [r load.count] 0
+            r debug reload
+            assert_equal [r load.count] 3
+        }
+    }
+}