Enforce LOD request concurrency limit.

src/main/java/no/jckf/dhsupport/core/PreGenerator.java

@@ -18,6 +18,7 @@
 
 package no.jckf.dhsupport.core;
 
+import no.jckf.dhsupport.core.configuration.Configuration;
 import no.jckf.dhsupport.core.configuration.DhsConfig;
 import no.jckf.dhsupport.core.database.models.LodModel;
 import no.jckf.dhsupport.core.dataobject.SectionPosition;
@@ -68,7 +69,12 @@ public class PreGenerator implements Runnable
 
     public void run()
     {
-        int rateLimit = this.world.getConfig().getInt(DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT);
+        Configuration worldConfig = this.world.getConfig();
+
+        // Fall back to the old key in case the server's config file is for an older plugin version.
+        int rateLimit = worldConfig.has(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT)
+            ? worldConfig.getInt(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT)
+            : worldConfig.getInt(DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT);
 
         int currentX = this.centerX;
         int currentZ = this.centerZ;

src/main/java/no/jckf/dhsupport/core/configuration/Configuration.java

@@ -118,4 +118,9 @@ public class Configuration
     {
         return (int) this.variables.compute(key, (k, v) -> v == null ? 1 : (int) v + 1);
     }
+
+    public int decrement(String key)
+    {
+        return (int) this.variables.compute(key, (k, v) -> v == null ? -1 : (int) v - 1);
+    }
 }

src/main/java/no/jckf/dhsupport/core/configuration/DhsConfig.java

@@ -32,8 +32,15 @@ public abstract class DhsConfig
 
     public static String DISTANT_GENERATION_ENABLED = "distant_generation_enabled";
 
+    /**
+     * @deprecated Replaced by CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT.
+     */
     public static String FULL_DATA_REQUEST_CONCURRENCY_LIMIT = "full_data_request_concurrency_limit";
 
+    public static String CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT = "client_lod_request_concurrency_limit";
+
+    public static String SERVER_LOD_REQUEST_CONCURRENCY_LIMIT = "server_lod_request_concurrency_limit";
+
     public static String REAL_TIME_UPDATES_ENABLED = "real_time_updates_enabled";
 
     public static String REAL_TIME_UPDATE_RADIUS = "real_time_update_radius";

src/main/java/no/jckf/dhsupport/core/handler/LodHandler.java

@@ -30,6 +30,7 @@ import no.jckf.dhsupport.core.world.WorldInterface;
 import org.bukkit.Bukkit;
 
 import java.util.UUID;
+import java.util.concurrent.atomic.AtomicInteger;
 
 public class LodHandler
 {
@@ -39,6 +40,8 @@ public class LodHandler
 
     protected PluginMessageHandler pluginMessageHandler;
 
+    protected AtomicInteger requestsInFlight = new AtomicInteger(0);
+
     public LodHandler(DhSupport dhSupport, PluginMessageHandler pluginMessageHandler)
     {
         this.dhSupport = dhSupport;
@@ -100,7 +103,35 @@ public class LodHandler
                 return;
             }
 
+            int clientRateLimit = playerConfig.getInt(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT, 0);
+            int serverRateLimit = dhsConfig.getInt(DhsConfig.SERVER_LOD_REQUEST_CONCURRENCY_LIMIT, 0);
+
+            boolean exceedsClientRateLimit = playerConfig.increment("active-requests") > clientRateLimit;
+            boolean exceedsServerRateLimit = serverRateLimit > 0 && this.requestsInFlight.incrementAndGet() > serverRateLimit;
+
+            if (exceedsClientRateLimit || exceedsServerRateLimit) {
+                if (serverRateLimit > 0) {
+                    this.requestsInFlight.decrementAndGet();
+                }
+
+                playerConfig.decrement("active-requests");
+
+                ExceptionMessage exceptionMessage = new ExceptionMessage();
+                exceptionMessage.isResponseTo(requestMessage);
+                exceptionMessage.setTypeId(ExceptionMessage.TYPE_RATE_LIMITED);
+                exceptionMessage.setMessage("Rate limited by the server");
+                this.pluginMessageHandler.sendPluginMessage(requestMessage.getSender(), exceptionMessage);
+                return;
+            }
+
             this.dhSupport.getLod(worldUuid, position)
+                .whenComplete((lodModel, exception) -> {
+                    if (serverRateLimit > 0) {
+                        this.requestsInFlight.decrementAndGet();
+                    }
+
+                    playerConfig.decrement("active-requests");
+                })
                 .thenAccept((lodModel) -> {
                     if (lodModel == null) {
                         ExceptionMessage exceptionMessage = new ExceptionMessage();

src/main/java/no/jckf/dhsupport/core/handler/PlayerConfigHandler.java

@@ -129,6 +129,11 @@ public class PlayerConfigHandler
                         keepValue = false;
                     }
 
+                    // If no value was found under the new key, read the old key to see if the server's config file is for an older plugin version.
+                    if (key.equals(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT) && dhsValue == null) {
+                        dhsValue = dhsConfig.get(DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT);
+                    }
+
                     // TODO: This is ugly. Move to comparator closures like in DH.
                     if (key.equals(DhsConfig.BORDER_CENTER_X)) {
                         keepValue = world.getWorldBorderX();

src/main/java/no/jckf/dhsupport/core/message/plugin/RemotePlayerConfigMessage.java

@@ -31,7 +31,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
         DhsConfig.BORDER_CENTER_X,
         DhsConfig.BORDER_CENTER_Z,
         DhsConfig.BORDER_RADIUS,
-        DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT,
+        DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT,
         DhsConfig.REAL_TIME_UPDATES_ENABLED,
         DhsConfig.REAL_TIME_UPDATE_RADIUS,
         DhsConfig.LOGIN_DATA_SYNC_ENABLED,
@@ -44,7 +44,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
 
     protected boolean distantGenerationEnabled;
 
-    protected int fullDataRequestConcurrencyLimit;
+    protected int clientLodRequestConcurrencyLimit;
 
     protected boolean realTimeUpdatesEnabled;
 
@@ -84,14 +84,14 @@ public class RemotePlayerConfigMessage extends PluginMessage
         return this.distantGenerationEnabled;
     }
 
-    public void setFullDataRequestConcurrencyLimit(int limit)
+    public void setClientLodRequestConcurrencyLimit(int limit)
     {
-        this.fullDataRequestConcurrencyLimit = limit;
+        this.clientLodRequestConcurrencyLimit = limit;
     }
 
-    public int getFullDataRequestConcurrencyLimit()
+    public int getClientLodRequestConcurrencyLimit()
     {
-        return this.fullDataRequestConcurrencyLimit;
+        return this.clientLodRequestConcurrencyLimit;
     }
 
     public void setRealTimeUpdatesEnabled(boolean enabled)
@@ -194,7 +194,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
         encoder.writeInt(this.borderCenterZ);
         encoder.writeInt(this.borderRadius);
 
-        encoder.writeInt(this.fullDataRequestConcurrencyLimit);
+        encoder.writeInt(this.clientLodRequestConcurrencyLimit);
 
         encoder.writeBoolean(this.realTimeUpdatesEnabled);
         encoder.writeInt(this.realTimeUpdateRadius);
@@ -216,7 +216,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
         this.borderCenterZ = decoder.readInt();
         this.borderRadius = decoder.readInt();
 
-        this.fullDataRequestConcurrencyLimit = decoder.readInt();
+        this.clientLodRequestConcurrencyLimit = decoder.readInt();
 
         this.realTimeUpdatesEnabled = decoder.readBoolean();
         this.realTimeUpdateRadius = decoder.readInt();
@@ -241,7 +241,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
         this.borderCenterZ = borderCenterZ == null ? 0 : borderCenterZ;
         this.borderRadius = borderRadius == null ? 0 : borderRadius;
 
-        this.fullDataRequestConcurrencyLimit = config.getInt(DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT);
+        this.clientLodRequestConcurrencyLimit = config.getInt(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT);
 
         this.realTimeUpdatesEnabled = config.getBool(DhsConfig.REAL_TIME_UPDATES_ENABLED);
         this.realTimeUpdateRadius = config.getInt(DhsConfig.REAL_TIME_UPDATE_RADIUS);
@@ -264,7 +264,7 @@ public class RemotePlayerConfigMessage extends PluginMessage
         config.set(DhsConfig.BORDER_CENTER_Z, this.borderCenterZ);
         config.set(DhsConfig.BORDER_RADIUS, this.borderRadius);
 
-        config.set(DhsConfig.FULL_DATA_REQUEST_CONCURRENCY_LIMIT, this.fullDataRequestConcurrencyLimit);
+        config.set(DhsConfig.CLIENT_LOD_REQUEST_CONCURRENCY_LIMIT, this.clientLodRequestConcurrencyLimit);
 
         config.set(DhsConfig.REAL_TIME_UPDATES_ENABLED, this.realTimeUpdatesEnabled);
         config.set(DhsConfig.REAL_TIME_UPDATE_RADIUS, this.realTimeUpdateRadius);

src/main/resources/config.yml

@@ -14,10 +14,15 @@ render_distance: 1024
 # Default: true
 distant_generation_enabled: true
 
-# Number of parallel LOD requests per client.
+# Maximum number of concurrent LOD requests per client.
 # Required.
 # Default: 20
-full_data_request_concurrency_limit: 20
+client_lod_request_concurrency_limit: 20
+
+# Maximum concurrent LOD requests server-wide, across all players. 0 = unlimited.
+# Optional.
+# Default: 0
+#server_lod_request_concurrency_limit: 100
 
 # Send LOD updates to players in real-time?
 # Required.
@@ -235,4 +240,4 @@ scheduler_threads: 4
 #debug: true
 
 # Don't touch :)
-config_version: 10
+config_version: 11