netty 使用注意事項

最近在使用netty的時候突然碰到這樣的一個警告:

 

2010-8-11 12:20:28 org.jboss.netty.util.internal.SharedResourceMisuseDetector
警告: You are creating too many MemoryAwareThreadPoolExecutor instances.  MemoryAwareThreadPoolExecutor is a shared resource that must be reused across the application, so that only a few instances are created.
2010-8-11 12:20:28 org.jboss.netty.util.internal.SharedResourceMisuseDetector
警告: You are creating too many HashedWheelTimer instances.  HashedWheelTimer is a shared resource that must be reused across the application, so that only a few instances are created.

說的是我在使用

MemoryAwareThreadPoolExecutor和HashedWheelTimer

的時候創造了太多的實例.後來一看源碼才發現問題所在!這兩個貌似都是線程池的對象,在各自的構造方法裏面,每實例一個對象就會使各自SharedResourceMisuseDetector(濫用共享資源探測器)加一.當超過256的時候就報警了!

private static final SharedResourceMisuseDetector misuseDetector =
        new SharedResourceMisuseDetector(MemoryAwareThreadPoolExecutor.class);
.....
// Misuse check
        misuseDetector.increase();

 後來再查看HashedWheelTimer的源代碼中還發現了這樣的提示:

<h3>Do not create many instances.</h3>
 *
 * {@link HashedWheelTimer} creates a new thread whenever it is instantiated and
 * started.  Therefore, you should make sure to create only one instance and
 * share it across your application.  One of the common mistakes, that makes
 * your application unresponsive, is to create a new instance in
 * {@link ChannelPipelineFactory}, which results in the creation of a new thread
 * for every connection.

大致就說不要創建太多的實例

之前我是這樣寫的

public class ServerPipelineFactory implements ChannelPipelineFactory {
...
@Override
	public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipeline = pipeline();
pipeline.addLast("executor", new ExecutionHandler(new OrderedMemoryAwareThreadPoolExecutor(16, 1048576, 1048576)));
pipeline.addLast("timeout", new ReadTimeoutHandler(new HashedWheelTimer(), 10));

 這樣以來每個channel獲取PipelineFactory的時候都會重新實例MemoryAwareThreadPoolExecutor和HashedWheelTimer,

當連接一多的時候就報警了!

 

根據這個提示我修改了ServerPipelineFactory,把他們做出單例的引用

 

public class ServerPipelineFactory implements ChannelPipelineFactory {
...
static OrderedMemoryAwareThreadPoolExecutor e = new OrderedMemoryAwareThreadPoolExecutor(16, 0, 0);
static HashedWheelTimer hashedWheelTimer = new HashedWheelTimer();
static ExecutionHandler executionHandler = new ExecutionHandler(e);
@Override
	public ChannelPipeline getPipeline() throws Exception {
ChannelPipeline pipeline = pipeline();
pipeline.addLast("executor", executionHandler );
pipeline.addLast("timeout", new ReadTimeoutHandler(hashedWheelTimer, 10));

 

 

這樣就不會再有SharedResourceMisuseDetector的警告了!