On 05/02/2016 00:30, Jeroen van Ooststroom wrote: > Hello, > > Using Tomcat 8.0.23 and Tomcat 8.0.30 with Java 1.7.0_25 on CentOS 5.11 > we are getting a stuck thread issue when our server is on high(er) load. > It seems to happen when one of our non-Container Threads invokes the > AsyncContext.complete() method while the AsyncStateMachine class’ state > class member is set to STARTING instead of STARTED, resulting in the > invocation of the Object’s wait() method in the > pauseNonContainerThread() method. It never seems to recover from this. > > I tried a couple of things within our source code trying to get around > this: > > 1. If HttpServletRequest.isAsyncStarted() returns true invoke > AsyncContext.complete(), but if it returns false
That should not be possible. And I think I have figured out what the problem is. Let me explain. The expected sequence of processing is: 0) Servlet.service() -> entry 1) Servlet.service() -> call startAsync() 2) Servlet.service() -> start a non-container thread to do some processing 3) Servlet.service() -> exits 4) non-container thread calls complete() Each connection has a dedicated async state machine that tracks the current state of the connection. At point 0 the state machine is in the state DISPATCHED (a.k.a. not async) At point 1 the state machine transitions to STARTING. At point 3 the state machine transitions to STARTED. At point 4 the state machine transitions to COMPLETING, a container thread is assigned which fires the onComplete() event for any listeners and then changes state to DISPATCHED. The point of the waits is to ensure that step 4) always occurs after step 3). If a non-container thread is paused, the aynsc post-processing code for container threads will unpause the thread once it completes. If a non-container thread calls complete() at an inappropriate time then an IllegalStateExcpetion should be thrown. The problem is that the non-container thread is paused before the check for the illegal state is made. Therefore, in the case where the non-container thread is making a call at an inappropriate time, it is paused and will never be unpaused. We need to check the state is valid before pausing the thread. I should be able to get this fixed today. We've just missed the recent 9.0.x and 8.0.x tags so I'd expect the fix to be available early next month. Mark --------------------------------------------------------------------- To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org For additional commands, e-mail: users-h...@tomcat.apache.org
