Remove throws Exception from ChannelHandler methods that handle o… (#11417)

Motivation:

At the moment all methods in `ChannelHandler` declare `throws Exception` as part of their method signature. While this is fine for methods that handle inbound events it is quite confusing for methods that handle outbound events. This comes due the fact that these methods also take a `ChannelPromise` which actually need to be fullfilled to signal back either success or failure. Define `throws...` for these methods is confusing at best. We should just always require the implementation to use the passed in promise to signal back success or failure. Doing so also clears up semantics in general. Due the fact that we can't "forbid" throwing `RuntimeException` we still need to handle this in some way tho. In this case we should just consider it a "bug" and so log it and close the `Channel` in question. The user should never have an exception "escape" their implementation and just use the promise. This also clears up the ownership of the passed in message etc.

As `flush(ChannelHandlerContext)` and `read(ChannelHandlerContext)` don't take a `ChannelPromise` as argument this also means that these methods can never produce an error. This makes kind of sense as these really are just "signals" for the underlying transports to do something. For `RuntimeException` the same rule is used as for other outbound event handling methods, which is logging and closing the `Channel`.

Motifications:

- Remove `throws Exception` from signature
- Adjust code to not throw and just notify the promise directly
- Adjust unit tests

Result:

Much cleaner API and semantics.

codec-http/src/main/java/io/netty/handler/codec/http/HttpClientUpgradeHandler.java

@@ -121,33 +121,33 @@ public class HttpClientUpgradeHandler extends HttpObjectAggregator {
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         ctx.bind(localAddress, promise);
     }
 
     @Override
     public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-                        ChannelPromise promise) throws Exception {
+                        ChannelPromise promise) {
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.disconnect(promise);
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.close(promise);
     }
 
     @Override
-    public void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.register(promise);
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.deregister(promise);
     }
 
@@ -157,8 +157,7 @@ public class HttpClientUpgradeHandler extends HttpObjectAggregator {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
-            throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (!(msg instanceof HttpRequest)) {
             ctx.write(msg, promise);
             return;
@@ -182,7 +181,7 @@ public class HttpClientUpgradeHandler extends HttpObjectAggregator {
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         ctx.flush();
     }
 

codec-http/src/main/java/io/netty/handler/codec/http/HttpServerKeepAliveHandler.java

@@ -65,7 +65,7 @@ public class HttpServerKeepAliveHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         // modify message on way out to add headers if needed
         if (msg instanceof HttpResponse) {
             final HttpResponse response = (HttpResponse) msg;

codec-http/src/main/java/io/netty/handler/codec/http/cors/CorsHandler.java

@@ -215,8 +215,7 @@ public class CorsHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
-            throws Exception {
+    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) {
         if (config != null && config.isCorsSupportEnabled() && msg instanceof HttpResponse) {
             final HttpResponse response = (HttpResponse) msg;
             if (setOrigin(response)) {

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/WebSocketProtocolHandler.java

@@ -82,7 +82,7 @@ abstract class WebSocketProtocolHandler extends MessageToMessageDecoder<WebSocke
     }
 
     @Override
-    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
+    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) {
         if (closeStatus == null || !ctx.channel().isActive()) {
             ctx.close(promise);
         } else {
@@ -96,7 +96,7 @@ abstract class WebSocketProtocolHandler extends MessageToMessageDecoder<WebSocke
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (closeSent != null) {
             ReferenceCountUtil.release(msg);
             promise.setFailure(new ClosedChannelException());

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/extensions/WebSocketClientExtensionHandler.java

@@ -56,7 +56,7 @@ public class WebSocketClientExtensionHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (msg instanceof HttpRequest && WebSocketExtensionUtil.isWebsocketUpgrade(((HttpRequest) msg).headers())) {
             HttpRequest request = (HttpRequest) msg;
             String headerValue = request.headers().getAsString(HttpHeaderNames.SEC_WEBSOCKET_EXTENSIONS);

codec-http/src/main/java/io/netty/handler/codec/http/websocketx/extensions/WebSocketServerExtensionHandler.java

@@ -99,7 +99,7 @@ public class WebSocketServerExtensionHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (msg instanceof HttpResponse) {
             HttpResponse httpResponse = (HttpResponse) msg;
             //checking the status is faster than looking at headers

codec-http/src/test/java/io/netty/handler/codec/http/websocketx/WebSocketHandshakeHandOverTest.java

@@ -17,7 +17,6 @@ package io.netty.handler.codec.http.websocketx;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
-import io.netty.channel.ChannelFuture;
 import io.netty.channel.ChannelFutureListener;
 import io.netty.channel.ChannelHandler;
 import io.netty.channel.ChannelHandlerContext;

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2ConnectionHandler.java

@@ -436,23 +436,23 @@ public class Http2ConnectionHandler extends ByteToMessageDecoder implements Http
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         ctx.bind(localAddress, promise);
     }
 
     @Override
     public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-                        ChannelPromise promise) throws Exception {
+                        ChannelPromise promise) {
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.disconnect(promise);
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (decoupleCloseAndGoAway) {
             ctx.close(promise);
             return;
@@ -508,12 +508,12 @@ public class Http2ConnectionHandler extends ByteToMessageDecoder implements Http
     }
 
     @Override
-    public void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.register(promise);
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.deregister(promise);
     }
 
@@ -523,7 +523,7 @@ public class Http2ConnectionHandler extends ByteToMessageDecoder implements Http
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         ctx.write(msg, promise);
     }
 

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2FrameCodec.java

@@ -342,7 +342,7 @@ public class Http2FrameCodec extends Http2ConnectionHandler {
             ctx.write(msg, promise);
         } else {
             ReferenceCountUtil.release(msg);
-            throw new UnsupportedMessageTypeException(msg);
+            promise.setFailure(new UnsupportedMessageTypeException(msg));
         }
     }
 

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2ConnectionRoundtripTest.java

@@ -647,12 +647,17 @@ public class Http2ConnectionRoundtripTest {
                     newPromise());
             clientChannel.pipeline().addFirst(new ChannelHandler() {
                 @Override
-                public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+                public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                     ReferenceCountUtil.release(msg);
 
-                    // Ensure we update the window size so we will try to write the rest of the frame while
-                    // processing the flush.
-                    http2Client.encoder().flowController().initialWindowSize(8);
+                    try {
+                        // Ensure we update the window size so we will try to write the rest of the frame while
+                        // processing the flush.
+                        http2Client.encoder().flowController().initialWindowSize(8);
+                    } catch (Http2Exception e) {
+                        promise.setFailure(e);
+                        return;
+                    }
                     promise.setFailure(new IllegalStateException());
                 }
             });

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2MultiplexTest.java

@@ -1278,7 +1278,7 @@ public abstract class Http2MultiplexTest<C extends Http2FrameCodec> {
         }
 
         @Override
-        public void flush(ChannelHandlerContext ctx) throws Exception {
+        public void flush(ChannelHandlerContext ctx) {
             didFlush = true;
             ctx.flush();
         }

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2StreamFrameToHttpObjectCodecTest.java

@@ -454,7 +454,7 @@ public class Http2StreamFrameToHttpObjectCodecTest {
         EmbeddedChannel ch = new EmbeddedChannel(ctx.newHandler(ByteBufAllocator.DEFAULT),
                 new ChannelHandler() {
                     @Override
-                    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+                    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                         if (msg instanceof Http2StreamFrame) {
                             frames.add((Http2StreamFrame) msg);
                             ctx.write(Unpooled.EMPTY_BUFFER, promise);

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

@@ -102,7 +102,7 @@ public abstract class ByteToMessageCodec<I> extends ChannelHandlerAdapter {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         encoder.write(ctx, msg, promise);
     }
 

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

@@ -91,29 +91,29 @@ public class DatagramPacketEncoder<M> extends MessageToMessageEncoder<AddressedE
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         encoder.bind(ctx, localAddress, promise);
     }
 
     @Override
     public void connect(
             ChannelHandlerContext ctx, SocketAddress remoteAddress,
-            SocketAddress localAddress, ChannelPromise promise) throws Exception {
+            SocketAddress localAddress, ChannelPromise promise) {
         encoder.connect(ctx, remoteAddress, localAddress, promise);
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         encoder.disconnect(ctx, promise);
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         encoder.close(ctx, promise);
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         encoder.deregister(ctx, promise);
     }
 
@@ -123,7 +123,7 @@ public class DatagramPacketEncoder<M> extends MessageToMessageEncoder<AddressedE
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         encoder.flush(ctx);
     }
 

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

@@ -96,7 +96,7 @@ public abstract class MessageToByteEncoder<I> extends ChannelHandlerAdapter {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         ByteBuf buf = null;
         try {
             if (acceptOutboundMessage(msg)) {
@@ -120,9 +120,9 @@ public abstract class MessageToByteEncoder<I> extends ChannelHandlerAdapter {
                 ctx.write(msg, promise);
             }
         } catch (EncoderException e) {
-            throw e;
+            promise.setFailure(e);
         } catch (Throwable e) {
-            throw new EncoderException(e);
+            promise.setFailure(new EncoderException(e));
         } finally {
             if (buf != null) {
                 buf.release();

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

@@ -112,7 +112,7 @@ public abstract class MessageToMessageCodec<INBOUND_IN, OUTBOUND_IN> extends Cha
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         encoder.write(ctx, msg, promise);
     }
 

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

@@ -78,7 +78,7 @@ public abstract class MessageToMessageEncoder<I> extends ChannelHandlerAdapter {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         CodecOutputList out = null;
         try {
             if (acceptOutboundMessage(msg)) {
@@ -99,9 +99,9 @@ public abstract class MessageToMessageEncoder<I> extends ChannelHandlerAdapter {
                 ctx.write(msg, promise);
             }
         } catch (EncoderException e) {
-            throw e;
+            promise.setFailure(e);
         } catch (Throwable t) {
-            throw new EncoderException(t);
+            promise.setFailure(new EncoderException(t));
         } finally {
             if (out != null) {
                 try {

codec/src/main/java/io/netty/handler/codec/compression/Bzip2Encoder.java

@@ -193,7 +193,7 @@ public class Bzip2Encoder extends MessageToByteEncoder<ByteBuf> {
     }
 
     @Override
-    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
+    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) {
         ChannelFuture f = finishEncode(ctx, ctx.newPromise());
         f.addListener((ChannelFutureListener) f1 -> ctx.close(promise));
 

codec/src/main/java/io/netty/handler/codec/compression/JdkZlibEncoder.java

@@ -262,7 +262,7 @@ public class JdkZlibEncoder extends ZlibEncoder {
     }
 
     @Override
-    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
+    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) {
         ChannelFuture f = finishEncode(ctx, ctx.newPromise());
         f.addListener((ChannelFutureListener) f1 -> ctx.close(promise));
 

codec/src/main/java/io/netty/handler/codec/compression/Lz4FrameEncoder.java

@@ -297,7 +297,7 @@ public class Lz4FrameEncoder extends MessageToByteEncoder<ByteBuf> {
     }
 
     @Override
-    public void flush(final ChannelHandlerContext ctx) throws Exception {
+    public void flush(final ChannelHandlerContext ctx) {
         if (buffer != null && buffer.isReadable()) {
             final ByteBuf buf = allocateBuffer(ctx, Unpooled.EMPTY_BUFFER, isPreferDirect(), false);
             flushBufferedData(buf);
@@ -366,7 +366,7 @@ public class Lz4FrameEncoder extends MessageToByteEncoder<ByteBuf> {
     }
 
     @Override
-    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
+    public void close(final ChannelHandlerContext ctx, final ChannelPromise promise) {
         ChannelFuture f = finishEncode(ctx, ctx.newPromise());
         f.addListener((ChannelFutureListener) f1 -> ctx.close(promise));
 

example/src/main/java/io/netty/example/haproxy/HAProxyHandler.java

@@ -33,7 +33,7 @@ public class HAProxyHandler extends ChannelOutboundHandlerAdapter {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         ChannelFuture future = ctx.write(msg, promise);
         if (msg instanceof HAProxyMessage) {
             future.addListener(new ChannelFutureListener() {

handler-proxy/src/main/java/io/netty/handler/proxy/HttpProxyHandler.java

@@ -286,28 +286,28 @@ public final class HttpProxyHandler extends ProxyHandler {
 
         @Override
         public void bind(ChannelHandlerContext ctx, SocketAddress localAddress,
-                         ChannelPromise promise) throws Exception {
+                         ChannelPromise promise) {
             codec.bind(ctx, localAddress, promise);
         }
 
         @Override
         public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-                            ChannelPromise promise) throws Exception {
+                            ChannelPromise promise) {
             codec.connect(ctx, remoteAddress, localAddress, promise);
         }
 
         @Override
-        public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+        public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
             codec.disconnect(ctx, promise);
         }
 
         @Override
-        public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+        public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
             codec.close(ctx, promise);
         }
 
         @Override
-        public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+        public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
             codec.deregister(ctx, promise);
         }
 
@@ -317,12 +317,12 @@ public final class HttpProxyHandler extends ProxyHandler {
         }
 
         @Override
-        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
             codec.write(ctx, msg, promise);
         }
 
         @Override
-        public void flush(ChannelHandlerContext ctx) throws Exception {
+        public void flush(ChannelHandlerContext ctx) {
             codec.flush(ctx);
         }
     }

handler-proxy/src/main/java/io/netty/handler/proxy/ProxyHandler.java

@@ -167,7 +167,7 @@ public abstract class ProxyHandler implements ChannelHandler {
     @Override
     public final void connect(
             ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-            ChannelPromise promise) throws Exception {
+            ChannelPromise promise) {
 
         if (destinationAddress != null) {
             promise.setFailure(new ConnectionPendingException());
@@ -394,7 +394,7 @@ public abstract class ProxyHandler implements ChannelHandler {
     }
 
     @Override
-    public final void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public final void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (finished) {
             writePendingWrites();
             ctx.write(msg, promise);
@@ -404,7 +404,7 @@ public abstract class ProxyHandler implements ChannelHandler {
     }
 
     @Override
-    public final void flush(ChannelHandlerContext ctx) throws Exception {
+    public final void flush(ChannelHandlerContext ctx) {
         if (finished) {
             writePendingWrites();
             ctx.flush();

handler/src/main/java/io/netty/handler/address/ResolveAddressHandler.java

@@ -28,8 +28,8 @@ import java.net.SocketAddress;
 
 /**
  * {@link ChannelHandler} which will resolve the {@link SocketAddress} that is passed to
- * {@link #connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)} if it is not already resolved
- * and the {@link AddressResolver} supports the type of {@link SocketAddress}.
+ * {@link ChannelHandler#connect(ChannelHandlerContext, SocketAddress, SocketAddress, ChannelPromise)} if it is not
+ * already resolved and the {@link AddressResolver} supports the type of {@link SocketAddress}.
  */
 @Sharable
 public class ResolveAddressHandler implements ChannelHandler {
@@ -42,7 +42,7 @@ public class ResolveAddressHandler implements ChannelHandler {
 
     @Override
     public void connect(final ChannelHandlerContext ctx, SocketAddress remoteAddress,
-                        final SocketAddress localAddress, final ChannelPromise promise)  {
+                        final SocketAddress localAddress, final ChannelPromise promise) {
         AddressResolver<? extends SocketAddress> resolver = resolverGroup.getResolver(ctx.executor());
         if (resolver.isSupported(remoteAddress) && !resolver.isResolved(remoteAddress)) {
             resolver.resolve(remoteAddress).addListener((FutureListener<SocketAddress>) future -> {

handler/src/main/java/io/netty/handler/flush/FlushConsolidationHandler.java

@@ -36,8 +36,8 @@ import java.util.concurrent.Future;
  * in most cases (where write latency can be traded with throughput) a good idea to try to minimize flush operations
  * as much as possible.
  * <p>
- * If a read loop is currently ongoing, {@link #flush(ChannelHandlerContext)} will not be passed on to the next
- * {@link ChannelHandler} in the {@link ChannelPipeline}, as it will pick up any pending flushes when
+ * If a read loop is currently ongoing, {@link ChannelHandler#flush(ChannelHandlerContext)} will not be passed on to
+ * the next {@link ChannelHandler} in the {@link ChannelPipeline}, as it will pick up any pending flushes when
  * {@link #channelReadComplete(ChannelHandlerContext)} is triggered.
  * If no read loop is ongoing, the behavior depends on the {@code consolidateWhenNoReadInProgress} constructor argument:
  * <ul>
@@ -114,7 +114,7 @@ public class FlushConsolidationHandler implements ChannelHandler {
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         if (readInProgress) {
             // If there is still a read in progress we are sure we will see a channelReadComplete(...) call. Thus
             // we only need to flush if we reach the explicitFlushAfterFlushes limit.
@@ -155,14 +155,14 @@ public class FlushConsolidationHandler implements ChannelHandler {
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         // Try to flush one last time if flushes are pending before disconnect the channel.
         resetReadAndFlushIfNeeded(ctx);
         ctx.disconnect(promise);
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         // Try to flush one last time if flushes are pending before close the channel.
         resetReadAndFlushIfNeeded(ctx);
         ctx.close(promise);

handler/src/main/java/io/netty/handler/logging/LoggingHandler.java

@@ -222,7 +222,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "BIND", localAddress));
         }
@@ -232,7 +232,7 @@ public class LoggingHandler implements ChannelHandler {
     @Override
     public void connect(
             ChannelHandlerContext ctx,
-            SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+            SocketAddress remoteAddress, SocketAddress localAddress, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "CONNECT", remoteAddress, localAddress));
         }
@@ -240,7 +240,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "DISCONNECT"));
         }
@@ -248,7 +248,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "CLOSE"));
         }
@@ -256,7 +256,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "DEREGISTER"));
         }
@@ -280,7 +280,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "WRITE", msg));
         }
@@ -296,7 +296,7 @@ public class LoggingHandler implements ChannelHandler {
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         if (logger.isEnabled(internalLevel)) {
             logger.log(internalLevel, format(ctx, "FLUSH"));
         }

handler/src/main/java/io/netty/handler/pcap/PcapWriteHandler.java

@@ -239,7 +239,7 @@ public final class PcapWriteHandler extends ChannelDuplexHandler implements Clos
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (!isClosed) {
             if (ctx.channel() instanceof SocketChannel) {
                 handleTCP(ctx, msg, true);

handler/src/main/java/io/netty/handler/ssl/SslHandler.java

@@ -475,7 +475,8 @@ public class SslHandler extends ByteToMessageDecoder {
      * Sets the number of bytes to pass to each {@link SSLEngine#wrap(ByteBuffer[], int, int, ByteBuffer)} call.
      * <p>
      * This value will partition data which is passed to write
-     * {@link #write(ChannelHandlerContext, Object, ChannelPromise)}. The partitioning will work as follows:
+     * {@link ChannelHandler#write(ChannelHandlerContext, Object, ChannelPromise)}.
+     * The partitioning will work as follows:
      * <ul>
      * <li>If {@code wrapDataSize <= 0} then we will write each data chunk as is.</li>
      * <li>If {@code wrapDataSize > data size} then we will attempt to aggregate multiple data chunks together.</li>
@@ -700,35 +701,35 @@ public class SslHandler extends ByteToMessageDecoder {
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         ctx.bind(localAddress, promise);
     }
 
     @Override
     public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-                        ChannelPromise promise) throws Exception {
+                        ChannelPromise promise) {
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
     @Override
-    public void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.register(promise);
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.deregister(promise);
     }
 
     @Override
     public void disconnect(final ChannelHandlerContext ctx,
-                           final ChannelPromise promise) throws Exception {
+                           final ChannelPromise promise) {
         closeOutboundAndChannel(ctx, promise, true);
     }
 
     @Override
     public void close(final ChannelHandlerContext ctx,
-                      final ChannelPromise promise) throws Exception {
+                      final ChannelPromise promise) {
         closeOutboundAndChannel(ctx, promise, false);
     }
 
@@ -746,7 +747,7 @@ public class SslHandler extends ByteToMessageDecoder {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (!(msg instanceof ByteBufConvertible)) {
             UnsupportedMessageTypeException exception = new UnsupportedMessageTypeException(msg, ByteBuf.class);
             ReferenceCountUtil.safeRelease(msg);
@@ -760,7 +761,7 @@ public class SslHandler extends ByteToMessageDecoder {
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         // Do not encrypt the first write request if this handler is
         // created with startTLS flag turned on.
         if (startTls && !isStateSet(STATE_SENT_FIRST_MESSAGE)) {
@@ -781,7 +782,6 @@ public class SslHandler extends ByteToMessageDecoder {
             wrapAndFlush(ctx);
         } catch (Throwable cause) {
             setHandshakeFailure(ctx, cause);
-            throw cause;
         }
     }
 
@@ -1832,7 +1832,7 @@ public class SslHandler extends ByteToMessageDecoder {
     }
 
     private void closeOutboundAndChannel(
-            final ChannelHandlerContext ctx, final ChannelPromise promise, boolean disconnect) throws Exception {
+            final ChannelHandlerContext ctx, final ChannelPromise promise, boolean disconnect)  {
         setState(STATE_OUTBOUND_CLOSED);
         engine.closeOutbound();
 
@@ -1868,7 +1868,7 @@ public class SslHandler extends ByteToMessageDecoder {
         }
     }
 
-    private void flush(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    private void flush(ChannelHandlerContext ctx, ChannelPromise promise) {
         if (pendingUnencryptedWrites != null) {
             pendingUnencryptedWrites.add(Unpooled.EMPTY_BUFFER, promise);
         } else {

handler/src/main/java/io/netty/handler/stream/ChunkedWriteHandler.java

@@ -114,12 +114,12 @@ public class ChunkedWriteHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         queue.add(new PendingWrite(msg, promise));
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         doFlush(ctx);
     }
 

handler/src/main/java/io/netty/handler/timeout/IdleStateHandler.java

@@ -297,7 +297,7 @@ public class IdleStateHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         // Allow writing with void promise if handler is only configured for read timeout events.
         if (writerIdleTimeNanos > 0 || allIdleTimeNanos > 0) {
             ctx.write(msg, promise).addListener(writeListener);

handler/src/main/java/io/netty/handler/timeout/WriteTimeoutHandler.java

@@ -104,7 +104,7 @@ public class WriteTimeoutHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         if (timeoutNanos > 0) {
             scheduleTimeout(ctx, promise);
         }

handler/src/main/java/io/netty/handler/traffic/AbstractTrafficShapingHandler.java

@@ -549,8 +549,7 @@ public abstract class AbstractTrafficShapingHandler implements ChannelHandler {
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
-            throws Exception {
+    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) {
         long size = calculateSize(msg);
         long now = TrafficCounter.milliSecondFromNano();
         if (size > 0) {

handler/src/main/java/io/netty/handler/traffic/GlobalChannelTrafficShapingHandler.java

@@ -648,8 +648,7 @@ public class GlobalChannelTrafficShapingHandler extends AbstractTrafficShapingHa
     }
 
     @Override
-    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
-            throws Exception {
+    public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) {
         long size = calculateSize(msg);
         long now = TrafficCounter.milliSecondFromNano();
         if (size > 0) {

handler/src/test/java/io/netty/handler/flush/FlushConsolidationHandlerTest.java

@@ -182,7 +182,7 @@ public class FlushConsolidationHandlerTest {
         return new EmbeddedChannel(
                 new ChannelHandler() {
                     @Override
-                    public void flush(ChannelHandlerContext ctx) throws Exception {
+                    public void flush(ChannelHandlerContext ctx) {
                         flushCount.incrementAndGet();
                         ctx.flush();
                     }

handler/src/test/java/io/netty/handler/ssl/SslHandlerTest.java

@@ -118,7 +118,7 @@ public class SslHandlerTest {
         SSLEngine engine = newClientModeSSLEngine();
         SslHandler handler = new SslHandler(engine) {
             @Override
-            public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+            public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                 super.write(ctx, msg, promise);
                 writeLatch.countDown();
             }

handler/src/test/java/io/netty/handler/stream/ChunkedWriteHandlerTest.java

@@ -616,7 +616,7 @@ public class ChunkedWriteHandlerTest {
 
         EmbeddedChannel ch = new EmbeddedChannel(new ChannelHandler() {
             @Override
-            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                 ReferenceCountUtil.release(msg);
                 // Calling close so we will drop all queued messages in the ChunkedWriteHandler.
                 ctx.close();

microbench/src/main/java/io/netty/microbench/channel/epoll/EpollSocketChannelBenchmark.java

@@ -104,8 +104,7 @@ public class EpollSocketChannelBenchmark extends AbstractMicrobenchmark {
                     }
 
                     @Override
-                    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise)
-                            throws Exception {
+                    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                         if (lastWritePromise != null) {
                             throw new IllegalStateException();
                         }

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

@@ -278,10 +278,9 @@ public interface ChannelHandler {
      * @param ctx           the {@link ChannelHandlerContext} for which the bind operation is made
      * @param localAddress  the {@link SocketAddress} to which it should bound
      * @param promise       the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception    thrown if an error occurs
      */
     @Skip
-    default void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) throws Exception {
+    default void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         ctx.bind(localAddress, promise);
     }
 
@@ -292,12 +291,11 @@ public interface ChannelHandler {
      * @param remoteAddress     the {@link SocketAddress} to which it should connect
      * @param localAddress      the {@link SocketAddress} which is used as source on connect
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
     default void connect(
             ChannelHandlerContext ctx, SocketAddress remoteAddress,
-            SocketAddress localAddress, ChannelPromise promise) throws Exception {
+            SocketAddress localAddress, ChannelPromise promise) {
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
@@ -306,10 +304,9 @@ public interface ChannelHandler {
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the disconnect operation is made
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    default void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.disconnect(promise);
     }
 
@@ -318,10 +315,9 @@ public interface ChannelHandler {
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the close operation is made
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    default void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.close(promise);
     }
 
@@ -330,10 +326,9 @@ public interface ChannelHandler {
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the register operation is made
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    default void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.register(promise);
     }
 
@@ -342,10 +337,9 @@ public interface ChannelHandler {
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the deregister operation is made
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    default void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         ctx.deregister(promise);
     }
 
@@ -360,15 +354,14 @@ public interface ChannelHandler {
     /**
      * Called once a write operation is made. The write operation will write the messages through the
      * {@link ChannelPipeline}. Those are then ready to be flushed to the actual {@link Channel} once
-     * {@link Channel#flush()} is called
+     * {@link Channel#flush()} is called.
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the write operation is made
      * @param msg               the message to write
      * @param promise           the {@link ChannelPromise} to notify once the operation completes
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    default void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         ctx.write(msg, promise);
     }
 
@@ -377,10 +370,9 @@ public interface ChannelHandler {
      * that are pending.
      *
      * @param ctx               the {@link ChannelHandlerContext} for which the flush operation is made
-     * @throws Exception        thrown if an error occurs
      */
     @Skip
-    default void flush(ChannelHandlerContext ctx) throws Exception {
+    default void flush(ChannelHandlerContext ctx) {
         ctx.flush();
     }
 }

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

@@ -243,7 +243,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     @Override
     public void bind(
             ChannelHandlerContext ctx,
-            SocketAddress localAddress, ChannelPromise promise) throws Exception {
+            SocketAddress localAddress, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.bind(outboundCtx, localAddress, promise);
@@ -256,7 +256,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     public void connect(
             ChannelHandlerContext ctx,
             SocketAddress remoteAddress, SocketAddress localAddress,
-            ChannelPromise promise) throws Exception {
+            ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.connect(outboundCtx, remoteAddress, localAddress, promise);
@@ -266,7 +266,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.disconnect(outboundCtx, promise);
@@ -276,7 +276,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.close(outboundCtx, promise);
@@ -286,7 +286,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.register(outboundCtx, promise);
@@ -296,7 +296,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.deregister(outboundCtx, promise);
@@ -316,7 +316,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.write(outboundCtx, msg, promise);
@@ -326,7 +326,7 @@ public class CombinedChannelDuplexHandler<I extends ChannelHandler, O extends Ch
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         assert ctx == outboundCtx.ctx;
         if (!outboundCtx.removed) {
             outboundHandler.flush(outboundCtx);

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

@@ -24,7 +24,6 @@ import io.netty.util.ReferenceCountUtil;
 import io.netty.util.ResourceLeakHint;
 import io.netty.util.concurrent.EventExecutor;
 import io.netty.util.internal.ObjectPool;
-import io.netty.util.internal.PromiseNotificationUtil;
 import io.netty.util.internal.ThrowableUtil;
 import io.netty.util.internal.StringUtil;
 import io.netty.util.internal.SystemPropertyUtil;
@@ -483,7 +482,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().bind(this, localAddress, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -523,7 +522,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().connect(this, remoteAddress, localAddress, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -562,7 +561,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().disconnect(this, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -595,7 +594,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().close(this, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, true, promise);
         }
     }
 
@@ -628,7 +627,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().register(this, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -661,7 +660,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().deregister(this, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -688,20 +687,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().read(this);
         } catch (Throwable t) {
-            invokeExceptionCaughtFromOutbound(t);
-        }
-    }
-
-    private void invokeExceptionCaughtFromOutbound(Throwable t) {
-        if ((executionMask & MASK_EXCEPTION_CAUGHT) != 0) {
-            invokeExceptionCaught(t);
-        } else {
-            DefaultChannelHandlerContext ctx = findContextInbound(MASK_EXCEPTION_CAUGHT);
-            if (ctx == null) {
-                notifyHandlerRemovedAlready();
-                return;
-            }
-            ctx.invokeExceptionCaught(t);
+            handleOutboundHandlerException(t, false, null);
         }
     }
 
@@ -722,7 +708,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().write(this, m, promise);
         } catch (Throwable t) {
-            notifyOutboundHandlerException(t, promise);
+            handleOutboundHandlerException(t, false, promise);
         }
     }
 
@@ -753,7 +739,7 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         try {
             handler().flush(this);
         } catch (Throwable t) {
-            invokeExceptionCaughtFromOutbound(t);
+            handleOutboundHandlerException(t, false, null);
         }
     }
 
@@ -817,8 +803,24 @@ final class DefaultChannelHandlerContext implements ChannelHandlerContext, Resou
         return writeAndFlush(msg, newPromise());
     }
 
-    private static void notifyOutboundHandlerException(Throwable cause, ChannelPromise promise) {
-        PromiseNotificationUtil.tryFailure(promise, cause, logger);
+    private void handleOutboundHandlerException(Throwable cause, boolean closeDidThrow, ChannelPromise promise) {
+        String msg = handler() + " threw an exception while handling an outbound event. This is most likely a bug";
+
+        if (promise != null && !promise.isDone()) {
+            // This is a "best-effort" approach to at least ensure the promise will be completed somehow.
+            promise.tryFailure(new IllegalStateException(msg, cause));
+        }
+
+        logger.warn("{}. This is most likely a bug, closing the channel.", msg, cause);
+        if (closeDidThrow) {
+            // Close itself did throw, just call close() directly and so have the next handler invoked. If we would
+            // call close() on the Channel we would risk an infinite-loop.
+            close();
+        } else {
+            // Let's close the channel. Calling close on the Channel ensure we start from the end of the pipeline
+            // and so give all handlers the chance to do something during close.
+            channel().close();
+        }
     }
 
     @Override

transport/src/test/java/io/netty/bootstrap/BootstrapTest.java

@@ -397,7 +397,7 @@ public class BootstrapTest {
         private ChannelPromise registerPromise;
 
         @Override
-        public void register(ChannelHandlerContext ctx, final ChannelPromise promise) throws Exception {
+        public void register(ChannelHandlerContext ctx, final ChannelPromise promise) {
             registerPromise = promise;
             latch.countDown();
             ChannelPromise newPromise = ctx.newPromise();

transport/src/test/java/io/netty/channel/DefaultChannelPipelineTest.java

@@ -1941,7 +1941,7 @@ public class DefaultChannelPipelineTest {
         final Queue<Object> outboundBuffer = new ArrayDeque<>();
 
         @Override
-        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
             outboundBuffer.add(msg);
         }
 

transport/src/test/java/io/netty/channel/LoggingHandler.java

@@ -30,51 +30,50 @@ final class LoggingHandler implements ChannelHandler {
     private final EnumSet<Event> interest = EnumSet.allOf(Event.class);
 
     @Override
-    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+    public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
         log(Event.WRITE);
         ctx.write(msg, promise);
     }
 
     @Override
-    public void flush(ChannelHandlerContext ctx) throws Exception {
+    public void flush(ChannelHandlerContext ctx) {
         log(Event.FLUSH);
         ctx.flush();
     }
 
     @Override
-    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise)
-            throws Exception {
+    public void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise) {
         log(Event.BIND, "localAddress=" + localAddress);
         ctx.bind(localAddress, promise);
     }
 
     @Override
     public void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
-            ChannelPromise promise) throws Exception {
+            ChannelPromise promise) {
         log(Event.CONNECT, "remoteAddress=" + remoteAddress + " localAddress=" + localAddress);
         ctx.connect(remoteAddress, localAddress, promise);
     }
 
     @Override
-    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
         log(Event.DISCONNECT);
         ctx.disconnect(promise);
     }
 
     @Override
-    public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
         log(Event.CLOSE);
         ctx.close(promise);
     }
 
     @Override
-    public void register(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void register(ChannelHandlerContext ctx, ChannelPromise promise) {
         log(Event.REGISTER);
         ctx.register(promise);
     }
 
     @Override
-    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+    public void deregister(ChannelHandlerContext ctx, ChannelPromise promise) {
         log(Event.DEREGISTER);
         ctx.deregister(promise);
     }

transport/src/test/java/io/netty/channel/PendingWriteQueueTest.java

@@ -44,7 +44,7 @@ public class PendingWriteQueueTest {
     public void testRemoveAndWrite() {
         assertWrite(new TestHandler() {
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 assertFalse(ctx.channel().isWritable(), "Should not be writable anymore");
 
                 ChannelFuture future = queue.removeAndWrite();
@@ -58,7 +58,7 @@ public class PendingWriteQueueTest {
     public void testRemoveAndWriteAll() {
         assertWrite(new TestHandler() {
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 assertFalse(ctx.channel().isWritable(), "Should not be writable anymore");
 
                 ChannelFuture future = queue.removeAndWriteAll();
@@ -73,7 +73,7 @@ public class PendingWriteQueueTest {
         assertWriteFails(new TestHandler() {
 
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 queue.removeAndFail(new TestException());
                 super.flush(ctx);
             }
@@ -84,7 +84,7 @@ public class PendingWriteQueueTest {
     public void testRemoveAndFailAll() {
         assertWriteFails(new TestHandler() {
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 queue.removeAndFailAll(new TestException());
                 super.flush(ctx);
             }
@@ -358,7 +358,7 @@ public class PendingWriteQueueTest {
         }
 
         @Override
-        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+        public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
             queue.add(msg, promise);
             assertFalse(queue.isEmpty());
             assertEquals(++expectedSize, queue.size());

transport/src/test/java/io/netty/channel/ReentrantChannelTest.java

@@ -173,7 +173,7 @@ public class ReentrantChannelTest extends BaseChannelTest {
             int flushCount;
 
             @Override
-            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                 if (writeCount < 5) {
                     writeCount++;
                     ctx.channel().flush();
@@ -182,7 +182,7 @@ public class ReentrantChannelTest extends BaseChannelTest {
             }
 
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 if (flushCount < 5) {
                     flushCount++;
                     ctx.channel().write(createTestBuf(2000));
@@ -227,7 +227,7 @@ public class ReentrantChannelTest extends BaseChannelTest {
         clientChannel.pipeline().addLast(new ChannelHandler() {
 
             @Override
-            public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+            public void write(final ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                 promise.addListener(future -> ctx.channel().close());
                 ctx.write(msg, promise);
                 ctx.channel().flush();
@@ -257,14 +257,8 @@ public class ReentrantChannelTest extends BaseChannelTest {
         clientChannel.pipeline().addLast(new ChannelHandler() {
 
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
-                throw new Exception("intentional failure");
-            }
-
-        }, new ChannelHandler() {
-            @Override
-            public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
-                ctx.close();
+            public void flush(ChannelHandlerContext ctx) {
+                throw new RuntimeException("intentional failure");
             }
         });
 

transport/src/test/java/io/netty/channel/embedded/EmbeddedChannelTest.java

@@ -255,7 +255,7 @@ public class EmbeddedChannelTest {
     public void testHasNoDisconnectSkipDisconnect() throws InterruptedException {
         EmbeddedChannel channel = new EmbeddedChannel(false, new ChannelHandler() {
             @Override
-            public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+            public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
                 promise.tryFailure(new Throwable());
             }
         });
@@ -347,8 +347,7 @@ public class EmbeddedChannelTest {
     public void testWriteLater() {
         EmbeddedChannel channel = new EmbeddedChannel(new ChannelHandler() {
             @Override
-            public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
-                    throws Exception {
+            public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) {
                 ctx.executor().execute(() -> ctx.write(msg, promise));
             }
         });
@@ -365,8 +364,7 @@ public class EmbeddedChannelTest {
         final int delay = 500;
         EmbeddedChannel channel = new EmbeddedChannel(new ChannelHandler() {
             @Override
-            public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise)
-                    throws Exception {
+            public void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise) {
                 ctx.executor().schedule(() -> {
                     ctx.writeAndFlush(msg, promise);
                 }, delay, TimeUnit.MILLISECONDS);
@@ -434,7 +432,7 @@ public class EmbeddedChannelTest {
         final CountDownLatch latch = new CountDownLatch(1);
         EmbeddedChannel channel = new EmbeddedChannel(new ChannelHandler() {
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 latch.countDown();
             }
         });
@@ -453,13 +451,13 @@ public class EmbeddedChannelTest {
 
         EmbeddedChannel channel = new EmbeddedChannel(new ChannelHandler() {
             @Override
-            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) throws Exception {
+            public void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise) {
                 ctx.write(msg, promise);
                 latch.countDown();
             }
 
             @Override
-            public void flush(ChannelHandlerContext ctx) throws Exception {
+            public void flush(ChannelHandlerContext ctx) {
                 flushCount.incrementAndGet();
             }
         });
@@ -572,13 +570,13 @@ public class EmbeddedChannelTest {
         private final Queue<Integer> queue = new ArrayDeque<>();
 
         @Override
-        public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+        public void disconnect(ChannelHandlerContext ctx, ChannelPromise promise) {
             queue.add(DISCONNECT);
             promise.setSuccess();
         }
 
         @Override
-        public void close(ChannelHandlerContext ctx, ChannelPromise promise) throws Exception {
+        public void close(ChannelHandlerContext ctx, ChannelPromise promise) {
             queue.add(CLOSE);
             promise.setSuccess();
         }