[jboss-user] [Performance Tuning] - Re: JBOSS Hanging Problem

Peter Johnson do-not-reply at jboss.com
Wed Mar 20 11:15:00 EDT 2013

Peter Johnson [https://community.jboss.org/people/peterj] created the discussion

"Re: JBOSS Hanging Problem"

To view the discussion, visit: https://community.jboss.org/message/803855#803855

That could be caused by one of two problems:

a) You have one or more requests that are "hanging". When they hang, the user might close the browser and try again. For example, there might be an infinite loop in the code which from that point on consumes processing power (and memory, but that usually is not too significant, but that all depends on the app). Or there might be some other haning issue such as a database deadlock. A thread dump will find this. (I have had people swear that there was no such issue in their code, yet while the system was idle - no requests coming in - the CPU was running at some high percentage. A thread dump showed exactly where the loop was.) Eventually, all of the threads in the http request thread pool get used up any no-one can get on the system any more. (Just yesterday I helped some colleagues find such an issue in their portal code using a thread dump.)

b) You have a memory leak. Eventually the heap fills up to the point that the JVM has to constantly take full garbage collections. You can verify this by turning on one of the GC logging options (-verbose:gc should be enough to catch a heap problem, also us -Xloggc:xxx to log to a file). One way to find a memory leak is to attach JVisualVM to the process and use it to take heap snapshots about 10 or 15 minutes apart while the system is busy. Then have it compare the heap snapshots and show you the differences. That should tell you which object(s) have increased in numbers.

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