Could not stop elegantly when running under tomcat

[ralf0131]

When deploying dubbo application under tomcat 8.5.30, the application could not stop elegantly. Below is the stack trace:

24-Apr-2018 09:50:57.637 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [dubbo-tomcat-demo-1.0.0-SNAPSHOT] appears to have started a thread named [New I/O server boss #1 ([id: 0x6f20c905, /0:0:0:0:0:0:0:0:20880])] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.base@10/sun.nio.ch.KQueueArrayWrapper.kevent0(Native Method)
 java.base@10/sun.nio.ch.KQueueArrayWrapper.poll(KQueueArrayWrapper.java:196)
 java.base@10/sun.nio.ch.KQueueSelectorImpl.doSelect(KQueueSelectorImpl.java:116)
 java.base@10/sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:89)
 java.base@10/sun.nio.ch.SelectorImpl.select(SelectorImpl.java:100)
 org.jboss.netty.channel.socket.nio.NioServerSocketPipelineSink$Boss.run(NioServerSocketPipelineSink.java:240)
 org.jboss.netty.util.ThreadRenamingRunnable.run(ThreadRenamingRunnable.java:108)
 org.jboss.netty.util.internal.DeadLockProofWorker$1.run(DeadLockProofWorker.java:44)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
 java.base@10/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 java.base@10/java.lang.Thread.run(Thread.java:844)
24-Apr-2018 09:50:57.638 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [dubbo-tomcat-demo-1.0.0-SNAPSHOT] appears to have started a thread named [dubbo-remoting-server-heartbeat-thread-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.base@10/jdk.internal.misc.Unsafe.park(Native Method)
 java.base@10/java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:234)
 java.base@10/java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2117)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1182)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:899)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1061)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1121)
 java.base@10/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 java.base@10/java.lang.Thread.run(Thread.java:844)
24-Apr-2018 09:50:57.640 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [dubbo-tomcat-demo-1.0.0-SNAPSHOT] appears to have started a thread named [DubboRegistryFailedRetryTimer-thread-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.base@10/jdk.internal.misc.Unsafe.park(Native Method)
 java.base@10/java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:234)
 java.base@10/java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2117)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1182)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:899)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1061)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1121)
 java.base@10/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 java.base@10/java.lang.Thread.run(Thread.java:844)
24-Apr-2018 09:50:57.647 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [dubbo-tomcat-demo-1.0.0-SNAPSHOT] appears to have started a thread named [DubboMulticastRegistryCleanTimer-thread-1] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.base@10/jdk.internal.misc.Unsafe.park(Native Method)
 java.base@10/java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:234)
 java.base@10/java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2117)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1182)
 java.base@10/java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:899)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1061)
 java.base@10/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1121)
 java.base@10/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
 java.base@10/java.lang.Thread.run(Thread.java:844)
24-Apr-2018 09:50:57.650 WARNING [localhost-startStop-2] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesThreads The web application [dubbo-tomcat-demo-1.0.0-SNAPSHOT] appears to have started a thread named [DubboShutdownHook] but has failed to stop it. This is very likely to create a memory leak. Stack trace of thread:
 java.base@10/java.lang.Thread.sleep(Native Method)
 com.alibaba.dubbo.config.ProtocolConfig.destroyAll(ProtocolConfig.java:162)
 com.alibaba.dubbo.config.AbstractConfig$1.run(AbstractConfig.java:82)
 java.base@10/java.lang.Thread.run(Thread.java:844)

It looks like there are several threads still running when web application stops.

[ralf0131]

The demo can be found in https://github.com/ralf0131/dubbo-demo/tree/master/dubbo-tomcat-demo

[ralf0131]

This issue has been fixed from 2.6.3 onwards.

[ralf0131]

Fixed by #1763