Fix scalability issue due to checkcast on context's invoke operations (…

…#12806)


Motivation:

ChannelDuplexHandler can implements both ChannelOutboundHandler and ChannelInboundHandler
causing a scalability issue due to checkcast due to https://bugs.openjdk.org/browse/JDK-8180450

Modifications:

Peeling-off invoke methods turning the checkcast vs interfaces into an instanceof
vs ChannelDuplexHandler, saving the scalability issue to happen.
Sadly, if users manually implements both ChannelOutboundHandler and ChannelInboundHandler
without extending ChannelDuplexHandler the fix won't be enough.

Result:

Scalable duplex channel handler operations.

microbench/src/main/java/io/netty/microbench/channel/DefaultChannelPipelineDuplexHandlerBenchmark.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2022 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+package io.netty.microbench.channel;
+
+import io.netty.channel.ChannelDuplexHandler;
+import io.netty.channel.ChannelHandlerContext;
+import io.netty.channel.ChannelInboundHandlerAdapter;
+import io.netty.channel.ChannelOutboundHandlerAdapter;
+import io.netty.channel.ChannelPipeline;
+import io.netty.channel.embedded.EmbeddedChannel;
+import io.netty.microbench.util.AbstractMicrobenchmark;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.annotations.Threads;
+import org.openjdk.jmh.annotations.Warmup;
+import org.openjdk.jmh.infra.Blackhole;
+
+@Warmup(iterations = 5, time = 1)
+@Measurement(iterations = 5, time = 1)
+@State(Scope.Thread)
+public class DefaultChannelPipelineDuplexHandlerBenchmark extends AbstractMicrobenchmark {
+
+    private ChannelPipeline pipeline;
+    private EmbeddedChannel channel;
+
+    @Param({"true", "false"})
+    private boolean duplex;
+
+    @Setup
+    public void setup() {
+        channel = new EmbeddedChannel() {
+            @Override
+            public void runPendingTasks() {
+                // NO-OP to reduce noise on flush
+            }
+        };
+        // disabling auto-read to reduce noise on flush
+        channel.config().setAutoRead(false);
+        pipeline = channel.pipeline();
+        pipeline.addLast(new ChannelInboundHandlerAdapter() {
+            @Override
+            public void channelReadComplete(final ChannelHandlerContext ctx) {
+                ctx.fireChannelReadComplete();
+            }
+        });
+        // Duplex handlers implements both out/in interfaces causing a scalability issue
+        // see https://bugs.openjdk.org/browse/JDK-8180450
+        if (duplex) {
+            pipeline.addLast(new ChannelDuplexHandler() {
+                @Override
+                public void channelReadComplete(final ChannelHandlerContext ctx) {
+                    ctx.fireChannelReadComplete();
+                }
+
+                @Override
+                public void flush(final ChannelHandlerContext ctx) {
+                    ctx.flush();
+                }
+            });
+            pipeline.addLast(new ChannelDuplexHandler() {
+                @Override
+                public void channelReadComplete(final ChannelHandlerContext ctx) {
+                    ctx.flush();
+                }
+            });
+        } else {
+            pipeline.addLast(new ChannelInboundHandlerAdapter() {
+                @Override
+                public void channelReadComplete(final ChannelHandlerContext ctx) {
+                    ctx.fireChannelReadComplete();
+                }
+            });
+            pipeline.addLast(new ChannelOutboundHandlerAdapter() {
+                @Override
+                public void flush(final ChannelHandlerContext ctx) {
+                    ctx.flush();
+                }
+            });
+            pipeline.addLast(new ChannelInboundHandlerAdapter() {
+                @Override
+                public void channelReadComplete(final ChannelHandlerContext ctx) {
+                    ctx.flush();
+                }
+            });
+        }
+    }
+
+    @TearDown
+    public void tearDown() {
+        pipeline.channel().close();
+    }
+
+    @Benchmark
+    public void propagateEvent(Blackhole hole) {
+        hole.consume(pipeline.fireChannelReadComplete());
+    }
+
+    @Benchmark
+    @Threads(4)
+    public void parallelPropagateEvent(Blackhole hole) {
+        hole.consume(pipeline.fireChannelReadComplete());
+    }
+}