085a61a310
Motivation: When Netty runs in a managed environment such as web application server, Netty needs to provide an explicit way to remove the thread-local variables it created to prevent class loader leaks. FastThreadLocal uses different execution paths for storing a thread-local variable depending on the type of the current thread. It increases the complexity of thread-local removal. Modifications: - Moved FastThreadLocal and FastThreadLocalThread out of the internal package so that a user can use it. - FastThreadLocal now keeps track of all thread local variables it has initialized, and calling FastThreadLocal.removeAll() will remove all thread-local variables of the caller thread. - Added FastThreadLocal.size() for diagnostics and tests - Introduce InternalThreadLocalMap which is a mixture of hard-wired thread local variable fields and extensible indexed variables - FastThreadLocal now uses InternalThreadLocalMap to implement a thread-local variable. - Added ThreadDeathWatcher.unwatch() so that PooledByteBufAllocator tells it to stop watching when its thread-local cache has been freed by FastThreadLocal.removeAll(). - Added FastThreadLocalTest to ensure that removeAll() works - Added microbenchmark for FastThreadLocal and JDK ThreadLocal - Upgraded to JMH 0.9 Result: - A user can remove all thread-local variables Netty created, as long as he or she did not exit from the current thread. (Note that there's no way to remove a thread-local variable from outside of the thread.) - FastThreadLocal exposes more useful operations such as isSet() because we always implement a thread local variable via InternalThreadLocalMap instead of falling back to JDK ThreadLocal. - FastThreadLocalBenchmark shows that this change improves the performance of FastThreadLocal even more.
82 lines
2.8 KiB
Java
82 lines
2.8 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.util.internal.InternalThreadLocalMap;
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import java.util.Map;
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import java.util.WeakHashMap;
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/**
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* Skelton 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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* 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="See 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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@Override
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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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