Add ChannelHandlerContext.isRemoved() to easily detect the removal of a ChannelHandler while in a method.

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

@@ -45,7 +45,6 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
     private volatile boolean singleDecode;
     private boolean decodeWasNull;
     private MessageList<Object> out;
-    private boolean removed;
 
     /**
      * If set then only one message is decoded on each {@link #messageReceived(ChannelHandlerContext, MessageList)}
@@ -92,7 +91,6 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
 
     @Override
     public final void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
-        removed = true;
         ByteBuf buf = internalBuffer();
         if (buf.isReadable()) {
             if (out == null) {
@@ -119,7 +117,7 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
             for (int i = 0; i < size; i ++) {
                 Object m = msgs.get(i);
                 // handler was removed in the loop
-                if (removed) {
+                if (ctx.isRemoved()) {
                     out.add(m);
                     continue;
                 }
@@ -165,12 +163,11 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
             throw new DecoderException(t);
         } finally {
             // release the cumulation if the handler was removed while messages are processed
-            if (removed) {
+            if (ctx.isRemoved()) {
                 if (cumulation != null) {
                     cumulation.release();
                     cumulation = null;
                 }
-                removed = false;
             }
             MessageList<Object> out = this.out;
             this.out = null;

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

@@ -66,7 +66,7 @@ public abstract class MessageToByteEncoder<I> extends ChannelOutboundHandlerAdap
             int size = msgs.size();
             for (int i = 0; i < size; i ++) {
                 Object m = msgs.get(i);
-                if (acceptOutboundMessage(m)) {
+                if (!ctx.isRemoved() && acceptOutboundMessage(m)) {
                     @SuppressWarnings("unchecked")
                     I cast = (I) m;
                     if (buf == null) {

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

@@ -63,7 +63,7 @@ public abstract class MessageToMessageDecoder<I> extends ChannelInboundHandlerAd
             int size = msgs.size();
             for (int i = 0; i < size; i ++) {
                 Object m = msgs.get(i);
-                if (acceptInboundMessage(m)) {
+                if (!ctx.isRemoved() && acceptInboundMessage(m)) {
                     @SuppressWarnings("unchecked")
                     I cast = (I) m;
                     try {

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

@@ -64,7 +64,7 @@ public abstract class MessageToMessageEncoder<I> extends ChannelOutboundHandlerA
             int size = msgs.size();
             for (int i = 0; i < size; i ++) {
                 Object m = msgs.get(i);
-                if (acceptOutboundMessage(m)) {
+                if (!ctx.isRemoved() && acceptOutboundMessage(m)) {
                     @SuppressWarnings("unchecked")
                     I cast = (I) m;
                     try {

transport/src/main/java/io/netty/channel/ChannelHandlerContext.java

@@ -150,6 +150,13 @@ public interface ChannelHandlerContext
      */
     ChannelHandler handler();
 
+    /**
+     * Return {@code true} if the {@link ChannelHandler} which belongs to this {@link ChannelHandler} was removed
+     * from the {@link ChannelPipeline}. Note that this method is only meant to be called from with in the
+     * {@link EventLoop}.
+     */
+    boolean isRemoved();
+
     @Override
     ChannelHandlerContext fireChannelRegistered();
 

transport/src/main/java/io/netty/channel/DefaultChannelHandlerContext.java

@@ -33,6 +33,7 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     private final DefaultChannelPipeline pipeline;
     private final String name;
     private final ChannelHandler handler;
+    private boolean removed;
 
     // Will be set to null if no child executor should be used, otherwise it will be set to the
     // child executor.
@@ -828,4 +829,13 @@ final class DefaultChannelHandlerContext extends DefaultAttributeMap implements
     public ChannelPromise voidPromise() {
         return channel.voidPromise();
     }
+
+    void setRemoved() {
+        removed = true;
+    }
+
+    @Override
+    public boolean isRemoved() {
+        return removed;
+    }
 }

transport/src/main/java/io/netty/channel/DefaultChannelPipeline.java

@@ -522,6 +522,7 @@ final class DefaultChannelPipeline implements ChannelPipeline {
         // Notify the complete removal.
         try {
             ctx.handler().handlerRemoved(ctx);
+            ctx.setRemoved();
         } catch (Throwable t) {
             fireExceptionCaught(new ChannelPipelineException(
                     ctx.handler().getClass().getName() + ".handlerRemoved() has thrown an exception.", t));

transport/src/main/java/io/netty/channel/SimpleChannelInboundHandler.java

@@ -58,7 +58,7 @@ public abstract class SimpleChannelInboundHandler<I> extends ChannelInboundHandl
         try {
             for (int i = 0; i < size; i++) {
                 Object msg = msgs.get(i);
-                if (acceptInboundMessage(msg)) {
+                if (!ctx.isRemoved() && acceptInboundMessage(msg)) {
                     if (!unaccepted.isEmpty()) {
                         ctx.fireMessageReceived(unaccepted);
                         unaccepted = MessageList.newInstance();