MetaQ接收数据客户端进入死循环

[yantzu]

情况偶现，症状就是程序不退出，进入死循环，CPU使用率100%，关键的堆栈如下：

"Thread-48" daemon prio=10 tid=0x00007f47a8048000 nid=0x73d2 in Object.wait() [0x00007f4796dec000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Object.wait(Native Method)
at java.lang.Thread.join(Thread.java:1289)
- locked <0x000000077858ab88> (a java.lang.Thread)
at com.taobao.metamorphosis.client.consumer.SimpleFetchManager.interruptRunners(SimpleFetchManager.java:146)
at com.taobao.metamorphosis.client.consumer.SimpleFetchManager.stopFetchRunner(SimpleFetchManager.java:128)
at com.taobao.metamorphosis.client.consumer.SimpleMessageConsumer.shutdown(SimpleMessageConsumer.java:162)
- locked <0x0000000776bdde10> (a com.taobao.metamorphosis.client.consumer.SimpleMessageConsumer)
at com.taobao.metamorphosis.client.MetaMessageSessionFactory.shutdown(MetaMessageSessionFactory.java:336)
- locked <0x0000000776bdde58> (a com.taobao.metamorphosis.client.MetaMessageSessionFactory)
at com.taobao.metamorphosis.client.MetaMessageSessionFactory$2.run(MetaMessageSessionFactory.java:244)

"fetch-Runner-0" daemon prio=10 tid=0x00007f4898002800 nid=0x6bdd runnable [0x00007f49294c5000]
java.lang.Thread.State: TIMED_WAITING (on object monitor)
at java.lang.Throwable.fillInStackTrace(Native Method)
at java.lang.Throwable.fillInStackTrace(Throwable.java:783)
- locked <0x000000073760cf20> (a java.lang.InterruptedException)
at java.lang.Throwable.(Throwable.java:250)
at java.lang.Exception.(Exception.java:54)
at java.lang.InterruptedException.(InterruptedException.java:57)
at java.lang.Object.wait(Native Method)
at com.taobao.gecko.core.nio.impl.SelectorManager.awaitReady(SelectorManager.java:147)
- locked <0x00000007702ecd40> (a com.taobao.gecko.core.nio.impl.SelectorManager)
at com.taobao.gecko.core.nio.impl.SelectorManager.registerChannel(SelectorManager.java:122)
at com.taobao.gecko.core.extension.GeckoTCPConnectorController.connect(GeckoTCPConnectorController.java:75)
at com.taobao.gecko.service.impl.DefaultRemotingClient.connect(DefaultRemotingClient.java:120)
at com.taobao.gecko.service.impl.DefaultRemotingClient.connect(DefaultRemotingClient.java:148)
- locked <0x0000000776b9dbc8> (a com.taobao.gecko.service.impl.DefaultRemotingClient)
at com.taobao.metamorphosis.client.RemotingClientWrapper.connectWithRef(RemotingClientWrapper.java:156)
- locked <0x0000000770384cb8> (a java.util.HashSet)
at com.taobao.metamorphosis.client.RemotingClientWrapper.connectWithRef(RemotingClientWrapper.java:192)
at com.taobao.metamorphosis.client.consumer.SimpleMessageConsumer.fetch(SimpleMessageConsumer.java:330)
at com.taobao.metamorphosis.client.consumer.SimpleFetchManager$FetchRequestRunner.processRequest(SimpleFetchManager.java:227)
at com.taobao.metamorphosis.client.consumer.SimpleFetchManager$FetchRequestRunner.run(SimpleFetchManager.java:215)
at java.lang.Thread.run(Thread.java:745)

[yantzu]

在程序直接调用System.exit()退出的时候，会调用metaq注册的shutdownhook，shutdownhook会调用SimpleFetchManager.stopFetchRunner()方法, 这个方法会判断条件this.requestQueue.size() < this.fetchRequestCount， 如果满足就会进入一个循环不停的等待。这个条件的退出，依赖于fetch线程退出，将requestQueue加回，但是此时fetch线程正好执行到代码SelectorManager.awaitReady()方法，SelectorManager此时已经被执行stop(), 所以条件一直被满足，进入一个死循环。结果就是fetch线程不退出，而shutdownhook等待fetch线程退出，jvm等待shutdownhook退出

[yantzu]

提交了一个gecko的PR，killme2008/gecko#5