Http2MultiplexCodec now propagates SETTINGS and GOAWAY frames in pipeline.

Motivation:

Allow the observation of SETTINGS frame by other handlers in the pipeline. For my particular use case this allows me to observe the value of MAX_CONCURRENT_STREAMS for a ChannelPool abstraction that supports HTTP/2 multiplexing. Beside this also forward GOAWAY frames.

Modification:

Always forward SETTINGS and GOAWAY frames

Result:

Settings / Goaway can now be observed in the parent channel. Previously it was not possible (to my knowledge) to capture the settings when using Http2MultiplexCodec.

codec-http2/src/main/java/io/netty/handler/codec/http2/Http2MultiplexCodec.java

@@ -66,7 +66,8 @@ import static java.lang.Math.min;
  * communication, closing of the channel is delayed until any inbound queue is drained with {@link
  * Channel#read()}, which follows the default behavior of channels in Netty. Applications are
  * free to close the channel in response to such events if they don't have use for any queued
- * messages.
+ * messages. Any connection level events like {@link Http2SettingsFrame} and {@link Http2GoAwayFrame}
+ * will be processed internally and also propagated down the pipeline for other handlers to act on.
  *
  * <p>Outbound streams are supported via the {@link Http2StreamChannelBootstrap}.
  *
@@ -164,8 +165,10 @@ public class Http2MultiplexCodec extends Http2FrameCodec {
     // Need to be volatile as accessed from within the DefaultHttp2StreamChannel in a multi-threaded fashion.
     volatile ChannelHandlerContext ctx;
 
-    Http2MultiplexCodec(Http2ConnectionEncoder encoder, Http2ConnectionDecoder decoder, Http2Settings initialSettings,
+    Http2MultiplexCodec(Http2ConnectionEncoder encoder,
-                    ChannelHandler inboundStreamHandler) {
+                        Http2ConnectionDecoder decoder,
+                        Http2Settings initialSettings,
+                        ChannelHandler inboundStreamHandler) {
         super(encoder, decoder, initialSettings);
         this.inboundStreamHandler = inboundStreamHandler;
     }
@@ -218,11 +221,15 @@ public class Http2MultiplexCodec extends Http2FrameCodec {
             onHttp2StreamFrame(((Http2MultiplexCodecStream) streamFrame.stream()).channel, streamFrame);
         } else if (frame instanceof Http2GoAwayFrame) {
             onHttp2GoAwayFrame(ctx, (Http2GoAwayFrame) frame);
+            // Allow other handlers to act on GOAWAY frame
+            ctx.fireChannelRead(frame);
         } else if (frame instanceof Http2SettingsFrame) {
             Http2Settings settings = ((Http2SettingsFrame) frame).settings();
             if (settings.initialWindowSize() != null) {
                 initialOutboundStreamWindow = settings.initialWindowSize();
             }
+            // Allow other handlers to act on SETTINGS frame
+            ctx.fireChannelRead(frame);
         } else {
             // Send any other frames down the pipeline
             ctx.fireChannelRead(frame);

codec-http2/src/test/java/io/netty/handler/codec/http2/CleartextHttp2ServerUpgradeHandlerTest.java

@@ -231,7 +231,7 @@ public class CleartextHttp2ServerUpgradeHandlerTest {
 
         ByteBuf settingsFrame = settingsFrameBuf();
 
-        assertFalse(channel.writeInbound(settingsFrame));
+        assertTrue(channel.writeInbound(settingsFrame));
 
         assertEquals(1, userEvents.size());
         assertTrue(userEvents.get(0) instanceof PriorKnowledgeUpgradeEvent);

codec-http2/src/test/java/io/netty/handler/codec/http2/Http2MultiplexCodecTest.java

@@ -41,11 +41,13 @@ import org.junit.Ignore;
 import org.junit.Test;
 
 import static io.netty.util.ReferenceCountUtil.release;
+import static org.hamcrest.Matchers.instanceOf;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThat;
 import static org.junit.Assert.assertTrue;
 
 /**
@@ -175,11 +177,15 @@ public class Http2MultiplexCodecTest {
 
     @Test
     public void unhandledHttp2FramesShouldBePropagated() {
-        Http2PingFrame decodedFrame = new DefaultHttp2PingFrame(0);
+        assertThat(parentChannel.readInbound(), instanceOf(Http2SettingsFrame.class));
 
-        codec.onHttp2Frame(decodedFrame);
+        Http2PingFrame pingFrame = new DefaultHttp2PingFrame(0);
-        Http2PingFrame receivedPing = parentChannel.readInbound();
+        codec.onHttp2Frame(pingFrame);
-        assertSame(receivedPing, decodedFrame);
+        assertSame(parentChannel.readInbound(), pingFrame);
+
+        DefaultHttp2GoAwayFrame goAwayFrame = new DefaultHttp2GoAwayFrame(1);
+        codec.onHttp2Frame(goAwayFrame);
+        assertSame(parentChannel.readInbound(), goAwayFrame);
     }
 
     @Test
@@ -619,8 +625,10 @@ public class Http2MultiplexCodecTest {
      */
     private final class TestableHttp2MultiplexCodec extends Http2MultiplexCodec {
 
-        public TestableHttp2MultiplexCodec(Http2ConnectionEncoder encoder, Http2ConnectionDecoder decoder,
+        public TestableHttp2MultiplexCodec(Http2ConnectionEncoder encoder,
-                                           Http2Settings initialSettings, ChannelHandler inboundStreamHandler) {
+                                           Http2ConnectionDecoder decoder,
+                                           Http2Settings initialSettings,
+                                           ChannelHandler inboundStreamHandler) {
             super(encoder, decoder, initialSettings, inboundStreamHandler);
         }
 
@@ -682,6 +690,7 @@ public class Http2MultiplexCodecTest {
     }
 
     private final class TestableHttp2MultiplexCodecBuilder extends Http2MultiplexCodecBuilder {
+
         TestableHttp2MultiplexCodecBuilder(boolean server, ChannelHandler childHandler) {
             super(server, childHandler);
         }