Share same ThreadLocal for all decoder/encoders to minimize memory usage

codec/src/main/java/io/netty/handler/codec/ByteToMessageDecoder.java

@@ -45,14 +45,6 @@ public abstract class ByteToMessageDecoder
     private volatile boolean singleDecode;
     private boolean decodeWasNull;
 
-    private static final ThreadLocal<OutputMessageBuf> decoderOutput =
-            new ThreadLocal<OutputMessageBuf>() {
-                @Override
-                protected OutputMessageBuf initialValue() {
-                    return new OutputMessageBuf();
-                }
-            };
-
     /**
      * If set then only one message is decoded on each {@link #inboundBufferUpdated(ChannelHandlerContext)} call.
      * This may be useful if you need to do some protocol upgrade and want to make sure nothing is mixed up.
@@ -91,7 +83,7 @@ public abstract class ByteToMessageDecoder
 
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
-        OutputMessageBuf out = decoderOutput();
+        OutputMessageBuf out = OutputMessageBuf.get();
         try {
             ByteBuf in = ctx.inboundByteBuffer();
             if (in.isReadable()) {
@@ -131,7 +123,7 @@ public abstract class ByteToMessageDecoder
     protected void callDecode(ChannelHandlerContext ctx, ByteBuf in) {
         boolean wasNull = false;
         boolean decoded = false;
-        OutputMessageBuf out = decoderOutput();
+        OutputMessageBuf out = OutputMessageBuf.get();
 
         assert out.isEmpty();
 
@@ -217,9 +209,4 @@ public abstract class ByteToMessageDecoder
     protected void decodeLast(ChannelHandlerContext ctx, ByteBuf in, MessageBuf<Object> out) throws Exception {
         decode(ctx, in, out);
     }
-
-    final OutputMessageBuf decoderOutput() {
-        return decoderOutput.get();
-    }
-
 }

codec/src/main/java/io/netty/handler/codec/MessageToMessageDecoder.java

@@ -42,14 +42,6 @@ import io.netty.channel.ChannelInboundMessageHandlerAdapter;
  */
 public abstract class MessageToMessageDecoder<I> extends ChannelInboundMessageHandlerAdapter<I> {
 
-    private static final ThreadLocal<OutputMessageBuf> decoderOutput =
-            new ThreadLocal<OutputMessageBuf>() {
-                @Override
-                protected OutputMessageBuf initialValue() {
-                    return new OutputMessageBuf();
-                }
-            };
-
     protected MessageToMessageDecoder() { }
 
     protected MessageToMessageDecoder(Class<? extends I> inboundMessageType) {
@@ -58,7 +50,7 @@ public abstract class MessageToMessageDecoder<I> extends ChannelInboundMessageHa
 
     @Override
     public final void messageReceived(ChannelHandlerContext ctx, I msg) throws Exception {
-        OutputMessageBuf out = decoderOutput.get();
+        OutputMessageBuf out = OutputMessageBuf.get();
         try {
             decode(ctx, msg, out);
         } finally {

codec/src/main/java/io/netty/handler/codec/MessageToMessageEncoder.java

@@ -39,13 +39,6 @@ import io.netty.channel.ChannelOutboundMessageHandlerAdapter;
  *
  */
 public abstract class MessageToMessageEncoder<I> extends ChannelOutboundMessageHandlerAdapter<I> {
-    private static final ThreadLocal<OutputMessageBuf> encoderOutput =
-            new ThreadLocal<OutputMessageBuf>() {
-                @Override
-                protected OutputMessageBuf initialValue() {
-                    return new OutputMessageBuf();
-                }
-            };
 
     protected MessageToMessageEncoder() { }
 
@@ -55,9 +48,7 @@ public abstract class MessageToMessageEncoder<I> extends ChannelOutboundMessageH
 
     @Override
     public final void flush(ChannelHandlerContext ctx, I msg) throws Exception {
-        OutputMessageBuf out = encoderOutput.get();
+        OutputMessageBuf out = OutputMessageBuf.get();
-
-        assert out.isEmpty();
 
         try {
             encode(ctx, msg, out);

codec/src/main/java/io/netty/handler/codec/OutputMessageBuf.java

@@ -20,15 +20,28 @@ import io.netty.buffer.DefaultMessageBuf;
 
 final class OutputMessageBuf extends DefaultMessageBuf<Object> {
     private int byteBufs;
-    public OutputMessageBuf() {
+
+    private static final ThreadLocal<OutputMessageBuf> output =
+            new ThreadLocal<OutputMessageBuf>() {
+                @Override
+                protected OutputMessageBuf initialValue() {
+                    return new OutputMessageBuf();
+                }
+
+                @Override
+                public OutputMessageBuf get() {
+                    OutputMessageBuf buf = super.get();
+                    // Just to be sure
+                    buf.clear();
+                    return buf;
+                }
+            };
+
+    static OutputMessageBuf get() {
+        return output.get();
     }
 
-    public OutputMessageBuf(int initialCapacity) {
+    private OutputMessageBuf() {
-        super(initialCapacity);
-    }
-
-    public OutputMessageBuf(int initialCapacity, int maxCapacity) {
-        super(initialCapacity, maxCapacity);
     }
 
     @Override

codec/src/main/java/io/netty/handler/codec/ReplayingDecoder.java

@@ -364,7 +364,7 @@ public abstract class ReplayingDecoder<S> extends ByteToMessageDecoder {
 
     @Override
     public void channelInactive(ChannelHandlerContext ctx) throws Exception {
-        OutputMessageBuf out = decoderOutput();
+        OutputMessageBuf out = OutputMessageBuf.get();
 
         try {
             replayable.terminate();
@@ -412,7 +412,7 @@ public abstract class ReplayingDecoder<S> extends ByteToMessageDecoder {
     protected void callDecode(ChannelHandlerContext ctx, ByteBuf buf) {
         boolean wasNull = false;
         ByteBuf in = cumulation;
-        OutputMessageBuf out = decoderOutput();
+        OutputMessageBuf out = OutputMessageBuf.get();
         boolean decoded = false;
 
         assert out.isEmpty();