8f7ef1cabb
Motivation: Invoking ChannelHandlers is not free and can result in some overhead when the ChannelPipeline becomes very long. This is especially true if most handlers will just forward the call to the next handler in the pipeline. When the user extends Channel*HandlerAdapter we can easily detect if can just skip the handler and invoke the next handler in the pipeline directly. This reduce the overhead of dispatch but also reduce the call-stack in many cases. This backports https://github.com/netty/netty/pull/8723 and https://github.com/netty/netty/pull/8987 to 4.1 Modifications: Detect if we can skip the handler when walking the pipeline. Result: Reduce overhead for long pipelines. Benchmark (extraHandlers) Mode Cnt Score Error Units DefaultChannelPipelineBenchmark.propagateEventOld 4 thrpt 10 267313.031 ± 9131.140 ops/s DefaultChannelPipelineBenchmark.propagateEvent 4 thrpt 10 824825.673 ± 12727.594 ops/s
95 lines
3.2 KiB
Java
95 lines
3.2 KiB
Java
/*
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* Copyright 2013 The Netty Project
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*
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* The Netty Project licenses this file to you under the Apache License,
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* version 2.0 (the "License"); you may not use this file except in compliance
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* with the License. You may obtain a copy of the License at:
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*/
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package io.netty.channel;
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import io.netty.channel.ChannelHandlerMask.Skip;
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import io.netty.util.internal.InternalThreadLocalMap;
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import java.util.Map;
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/**
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* Skeleton implementation of a {@link ChannelHandler}.
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*/
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public abstract class ChannelHandlerAdapter implements ChannelHandler {
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// Not using volatile because it's used only for a sanity check.
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boolean added;
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/**
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* Throws {@link IllegalStateException} if {@link ChannelHandlerAdapter#isSharable()} returns {@code true}
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*/
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protected void ensureNotSharable() {
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if (isSharable()) {
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throw new IllegalStateException("ChannelHandler " + getClass().getName() + " is not allowed to be shared");
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}
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}
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/**
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* Return {@code true} if the implementation is {@link Sharable} and so can be added
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* to different {@link ChannelPipeline}s.
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*/
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public boolean isSharable() {
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/**
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* Cache the result of {@link Sharable} annotation detection to workaround a condition. We use a
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* {@link ThreadLocal} and {@link WeakHashMap} to eliminate the volatile write/reads. Using different
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* {@link WeakHashMap} instances per {@link Thread} is good enough for us and the number of
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* {@link Thread}s are quite limited anyway.
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*
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* See <a href="https://github.com/netty/netty/issues/2289">#2289</a>.
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*/
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Class<?> clazz = getClass();
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Map<Class<?>, Boolean> cache = InternalThreadLocalMap.get().handlerSharableCache();
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Boolean sharable = cache.get(clazz);
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if (sharable == null) {
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sharable = clazz.isAnnotationPresent(Sharable.class);
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cache.put(clazz, sharable);
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}
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return sharable;
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}
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/**
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* Do nothing by default, sub-classes may override this method.
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*/
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@Override
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public void handlerAdded(ChannelHandlerContext ctx) throws Exception {
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// NOOP
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}
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/**
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* Do nothing by default, sub-classes may override this method.
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*/
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@Override
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public void handlerRemoved(ChannelHandlerContext ctx) throws Exception {
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// NOOP
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}
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/**
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* Calls {@link ChannelHandlerContext#fireExceptionCaught(Throwable)} to forward
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* to the next {@link ChannelHandler} in the {@link ChannelPipeline}.
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*
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* Sub-classes may override this method to change behavior.
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*
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* @deprecated is part of {@link ChannelInboundHandler}
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*/
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@Skip
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@Override
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@Deprecated
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public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
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ctx.fireExceptionCaught(cause);
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}
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}
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