[Tomcat] Possible Denial of Service with WebSocket

[jfarcand]

If the client doesn't process the I/O operation fast enough, Tomcat dead lock on its blocking write operation

"SHARED-AsyncWrite-20" - Thread t@438
   java.lang.Thread.State: TIMED_WAITING
    at sun.misc.Unsafe.park(Native Method)
    - parking to wait for <666b6585> (a java.util.concurrent.CountDownLatch$Sync)
    at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireSharedNanos(AbstractQueuedSynchronizer.java:1033)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireSharedNanos(AbstractQueuedSynchronizer.java:1326)
    at java.util.concurrent.CountDownLatch.await(CountDownLatch.java:282)
    at org.apache.tomcat.util.net.NioEndpoint$KeyAttachment.awaitLatch(NioEndpoint.java:1571)
    at org.apache.tomcat.util.net.NioEndpoint$KeyAttachment.awaitWriteLatch(NioEndpoint.java:1574)
    at org.apache.tomcat.util.net.NioBlockingSelector.write(NioBlockingSelector.java:107)
    at org.apache.tomcat.util.net.NioSelectorPool.write(NioSelectorPool.java:174)
    at org.apache.tomcat.util.net.SecureNioChannel.flush(SecureNioChannel.java:121)
    at org.apache.coyote.http11.upgrade.UpgradeNioProcessor.flush(UpgradeNioProcessor.java:68)
    at org.apache.coyote.http11.upgrade.UpgradeOutbound.flush(UpgradeOutbound.java:30)
    at org.apache.catalina.websocket.WsOutbound.doWriteBytes(WsOutbound.java:395)
    at org.apache.catalina.websocket.WsOutbound.doWriteText(WsOutbound.java:423)
    at org.apache.catalina.websocket.WsOutbound.writeTextMessage(WsOutbound.java:170)
    - locked <4c4fc991> (a org.apache.catalina.websocket.WsOutbound)
    at org.atmosphere.container.version.TomcatWebSocket.write(TomcatWebSocket.java:75)
    at org.atmosphere.container.version.TomcatWebSocket.write(TomcatWebSocket.java:36)
    at org.atmosphere.cpr.AtmosphereResponse$3.write(AtmosphereResponse.java:695)
    at org.atmosphere.handler.AbstractReflectorAtmosphereHandler.onStateChange(AbstractReflectorAtmosphereHandler.java:136)
    at com.vmware.nee.listeners.PushAtmosphereHandlerService.super$2$onStateChange(PushAtmosphereHandlerService.groovy)
    at sun.reflect.GeneratedMethodAccessor1913.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:601)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1071)
    at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1110)
    at org.codehaus.groovy.runtime.ScriptBytecodeAdapter.invokeMethodOnSuperN(ScriptBytecodeAdapter.java:128)
    at com.vmware.nee.listeners.PushAtmosphereHandlerService.onStateChange(PushAtmosphereHandlerService.groovy:144)
    at org.atmosphere.cpr.DefaultBroadcaster.invokeOnStateChange(DefaultBroadcaster.java:1046)
    at org.atmosphere.cpr.DefaultBroadcaster$WriteOperation.call(DefaultBroadcaster.java:1082)
    at org.atmosphere.cpr.DefaultBroadcaster.prepareInvokeOnStateChange(DefaultBroadcaster.java:1058)
    at org.atmosphere.cpr.DefaultBroadcaster.executeAsyncWrite(DefaultBroadcaster.java:956)
    at org.atmosphere.cpr.DefaultBroadcaster$3.run(DefaultBroadcaster.java:600)
    - locked <216d4dfe> (a org.atmosphere.cpr.AtmosphereResourceImpl)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
    at java.util.concurrent.FutureTask.run(FutureTask.java:166)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
    at java.lang.Thread.run(Thread.java:722) 

The only solution is to interrupt the calling thread.