Remove condition in ChannelHandlerAdapter.isSharable() by caching the result of the annotation lookup.
Motivation: Remove the synchronization bottleneck and so speed up things Modifications: Introduce a ThreadLocal cache that holds mappings between classes of ChannelHandlerAdapater implementations and the result of checking if the @Sharable annotation is present. This way we only will need to do the real check one time and server the other calls via the cache. A ThreadLocal and WeakHashMap combo is used to implement the cache as this way we can minimize the conditions while still be sure we not leak class instances in containers. Result: Less conditions during adding ChannelHandlerAdapter to the ChannelPipeline
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@ -89,7 +89,7 @@ public abstract class ByteToMessageCodec<I> extends ChannelDuplexHandler {
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}
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}
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private void checkForSharableAnnotation() {
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private void checkForSharableAnnotation() {
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if (getClass().isAnnotationPresent(Sharable.class)) {
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if (isSharable()) {
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throw new IllegalStateException("@Sharable annotation is not allowed");
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throw new IllegalStateException("@Sharable annotation is not allowed");
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}
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}
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}
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}
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@ -52,7 +52,7 @@ public abstract class ByteToMessageDecoder extends ChannelInboundHandlerAdapter
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private boolean first;
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private boolean first;
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protected ByteToMessageDecoder() {
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protected ByteToMessageDecoder() {
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if (getClass().isAnnotationPresent(Sharable.class)) {
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if (isSharable()) {
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throw new IllegalStateException("@Sharable annotation is not allowed");
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throw new IllegalStateException("@Sharable annotation is not allowed");
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}
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}
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}
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}
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@ -16,11 +16,31 @@
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package io.netty.channel;
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package io.netty.channel;
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import java.util.Map;
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import java.util.WeakHashMap;
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/**
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/**
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* Skelton implementation of a {@link ChannelHandler}.
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* Skelton implementation of a {@link ChannelHandler}.
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*/
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*/
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public abstract class ChannelHandlerAdapter implements ChannelHandler {
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public abstract class ChannelHandlerAdapter implements ChannelHandler {
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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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private static final ThreadLocal<Map<Class<?>, Boolean>> SHARABLE_CACHE =
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new ThreadLocal<Map<Class<?>, Boolean>>() {
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@Override
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protected Map<Class<?>, Boolean> initialValue() {
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// Start with small capacity to keep memory overhead as low as possible.
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return new WeakHashMap<Class<?>, Boolean>(4);
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}
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};
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// Not using volatile because it's used only for a sanity check.
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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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boolean added;
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@ -29,7 +49,14 @@ public abstract class ChannelHandlerAdapter implements ChannelHandler {
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* to different {@link ChannelPipeline}s.
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* to different {@link ChannelPipeline}s.
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*/
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*/
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public boolean isSharable() {
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public boolean isSharable() {
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return getClass().isAnnotationPresent(Sharable.class);
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Class<?> clazz = getClass();
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Map<Class<?>, Boolean> cache = SHARABLE_CACHE.get();
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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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/**
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/**
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