add mechanism to deduplicate outgoing requests

src/main/java/electrosphere/client/terrain/cache/ClientTerrainCache.java

@@ -5,6 +5,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.Semaphore;
 
 import org.joml.Vector3i;
 
@@ -50,6 +51,11 @@ public class ClientTerrainCache {
      * A map of chunk to its world position
      */
     Map<ChunkData,Vector3i> chunkPositionMap = new ConcurrentHashMap<ChunkData,Vector3i>();
+
+    /**
+     * The lock on the terrain cache
+     */
+    Semaphore lock = new Semaphore(1);
     
     /**
      * Constructor
@@ -67,6 +73,7 @@ public class ClientTerrainCache {
      * @param chunkData The chunk data to add at the specified positions
      */
     public void addChunkDataToCache(int worldX, int worldY, int worldZ, ChunkData chunkData){
+        lock.acquireUninterruptibly();
         Map<Long,ChunkData> cache = this.getCache(chunkData.getStride());
         cache.put(getKey(worldX,worldY,worldZ),chunkData);
         chunkPositionMap.put(chunkData,new Vector3i(worldX,worldY,worldZ));
@@ -74,16 +81,19 @@ public class ClientTerrainCache {
             Long currentChunk = cacheList.remove(0);
             cache.remove(currentChunk);
         }
+        lock.release();
     }
 
     /**
      * Evicts all chunks from the cache
      */
     public void evictAll(){
+        lock.acquireUninterruptibly();
         this.cacheList.clear();
         this.cacheMapFullRes.clear();
         this.cacheMapHalfRes.clear();
         this.chunkPositionMap.clear();
+        lock.release();
     }
     
     
@@ -107,7 +117,10 @@ public class ClientTerrainCache {
      * @return True if the cache contains chunk data at the specified point, false otherwise
      */
     public boolean containsChunkDataAtWorldPoint(int worldX, int worldY, int worldZ, int stride){
-        return this.getCache(stride).containsKey(getKey(worldX,worldY,worldZ));
+        lock.acquireUninterruptibly();
+        boolean rVal = this.getCache(stride).containsKey(getKey(worldX,worldY,worldZ));
+        lock.release();
+        return rVal;
     }
     
     
@@ -123,7 +136,10 @@ public class ClientTerrainCache {
      * @return The chunk data if it exists, null otherwise
      */
     public ChunkData getSubChunkDataAtPoint(int worldX, int worldY, int worldZ, int stride){
-        return this.getCache(stride).get(getKey(worldX,worldY,worldZ));
+        lock.acquireUninterruptibly();
+        ChunkData rVal = this.getCache(stride).get(getKey(worldX,worldY,worldZ));
+        lock.release();
+        return rVal;
     }
 
     /**

src/main/java/electrosphere/client/terrain/cells/ClientDrawCellManager.java

@@ -602,8 +602,9 @@ public class ClientDrawCellManager {
     /**
      * Requests all chunks for a given draw cell
      * @param cell The cell
+     * @return true if all cells were successfully requested, false otherwise
      */
-    private void requestChunks(WorldOctTree.FloatingChunkTreeNode<DrawCell> node, List<DrawCellFace> highResFaces){
+    private boolean requestChunks(WorldOctTree.FloatingChunkTreeNode<DrawCell> node, List<DrawCellFace> highResFaces){
         DrawCell cell = node.getData();
         int lod = this.chunkTree.getMaxLevel() - node.getLevel();
         int spacingFactor = (int)Math.pow(2,lod);
@@ -622,7 +623,9 @@ public class ClientDrawCellManager {
                         ){
                             //client should request chunk data from server for each chunk necessary to create the model
                             LoggerInterface.loggerNetworking.DEBUG("(Client) Send Request for terrain at " + posToCheck);
-                            Globals.clientTerrainManager.requestChunk(posToCheck.x, posToCheck.y, posToCheck.z, lod);
+                            if(!Globals.clientTerrainManager.requestChunk(posToCheck.x, posToCheck.y, posToCheck.z, lod)){
+                                return false;
+                            }
                     }
                 }
             }
@@ -666,12 +669,15 @@ public class ClientDrawCellManager {
                             !Globals.clientTerrainManager.containsChunkDataAtWorldPoint(posToCheck.x, posToCheck.y, posToCheck.z, highResLod)
                             ){
                             LoggerInterface.loggerNetworking.DEBUG("(Client) Send Request for terrain at " + posToCheck);
-                            Globals.clientTerrainManager.requestChunk(posToCheck.x, posToCheck.y, posToCheck.z, highResLod);
+                            if(!Globals.clientTerrainManager.requestChunk(posToCheck.x, posToCheck.y, posToCheck.z, highResLod)){
+                                return false;
+                            }
                         }
                     }
                 }
             }
         }
+        return true;
     }
 
     /**

src/main/java/electrosphere/client/terrain/manager/ClientTerrainManager.java

@@ -6,7 +6,9 @@ import java.nio.IntBuffer;
 import java.util.Collection;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.UUID;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.concurrent.Semaphore;
 
@@ -25,6 +27,7 @@ import electrosphere.renderer.meshgen.TerrainChunkModelGeneration;
 import electrosphere.renderer.model.Model;
 import electrosphere.server.terrain.manager.ServerTerrainChunk;
 import electrosphere.server.terrain.manager.ServerTerrainManager;
+import io.github.studiorailgun.HashUtils;
 
 /**
  * Manages terrain storage and access on the client
@@ -58,6 +61,11 @@ public class ClientTerrainManager {
 
     //The queue of terrain chunk data to be buffered to gpu
     static List<TerrainChunkGenQueueItem> terrainChunkGenerationQueue = new CopyOnWriteArrayList<TerrainChunkGenQueueItem>();
+
+    /**
+     * Tracks what outgoing requests are currently active
+     */
+    Map<Long,Boolean> requestedMap = new ConcurrentHashMap<Long,Boolean>();
     
     /**
      * Constructor
@@ -134,6 +142,8 @@ public class ClientTerrainManager {
                         message.getworldX(), message.getworldY(), message.getworldZ(), 
                         data
                     );
+                    //remove from request map
+                    this.requestedMap.remove(this.getRequestKey(message.getworldX(), message.getworldY(), message.getworldZ(), message.getchunkResolution()));
                 } break;
                 default:
                     LoggerInterface.loggerEngine.WARNING("ClientTerrainManager: unhandled network message of type" + message.getMessageSubtype());
@@ -192,14 +202,23 @@ public class ClientTerrainManager {
      * @param worldY the world y coordinate of the chunk
      * @param worldZ the world z coordinate of the chunk
      * @param stride The stride of the data
+     * @return true if the request was successfully sent, false otherwise
      */
-    public void requestChunk(int worldX, int worldY, int worldZ, int stride){
+    public boolean requestChunk(int worldX, int worldY, int worldZ, int stride){
-        Globals.clientConnection.queueOutgoingMessage(TerrainMessage.constructRequestReducedChunkDataMessage(
+        boolean rVal = false;
-            worldX,
+        lock.acquireUninterruptibly();
-            worldY,
+        if(!this.requestedMap.containsKey(this.getRequestKey(worldX, worldY, worldZ, stride))){
-            worldZ,
+            Globals.clientConnection.queueOutgoingMessage(TerrainMessage.constructRequestReducedChunkDataMessage(
-            stride
+                worldX,
-        ));
+                worldY,
+                worldZ,
+                stride
+            ));
+            this.requestedMap.put(this.getRequestKey(worldX, worldY, worldZ, stride), true);
+            rVal = true;
+        }
+        lock.release();
+        return rVal;
     }
     
     /**
@@ -273,5 +292,17 @@ public class ClientTerrainManager {
     public Vector3i getPositionOfChunk(ChunkData chunk){
         return terrainCache.getChunkPosition(chunk);
     }
+
+    /**
+     * Gets the key for a given request
+     * @param worldX The world x coordinate
+     * @param worldY The world y coordinate
+     * @param worldZ The world z coordinate
+     * @param stride The stride of the data
+     * @return The key
+     */
+    private Long getRequestKey(int worldX, int worldY, int worldZ, int stride){
+        return (long)HashUtils.cantorHash(worldY, worldZ, worldZ);
+    }
     
 }