[jboss-jira] [JBoss JIRA] (WFCORE-1093) TempFileProviderService threads consume high CPU

[Aaron Ogburn (JIRA)]

Aaron Ogburn created WFCORE-1093:
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             Summary: TempFileProviderService threads consume high CPU
                 Key: WFCORE-1093
                 URL: https://issues.jboss.org/browse/WFCORE-1093
             Project: WildFly Core
          Issue Type: Bug
          Components: Server
            Reporter: Aaron Ogburn
            Assignee: Jason Greene


TempFileProviderService threads consume high CPU as they poll their non empty task queue.  This is ultimately due to a flaw in the JDK ThreadPoolExecutor code (https://bugs.openjdk.java.net/browse/JDK-8129861), impacting ScheduledThreadPoolExecutors that use a core size of 0 and a default 0 keepalive timeout.  

While the executor queue is not empty, the executor does not allow the pool to go below 1 thread.  So the one remaining work thread keeps looping over its poll call with a 0 timeout.  Options to protect JBoss from this are:

1) Set a keepalive timeout on the executor so the poll has a duration and the worker run loop isn't so busy
2) Or set the Executor core pool size to >0.  The worker thread would then use a blocking take() call on its queue instead of a constant 0 second poll calls.  The side effect of this change is that the thread pool wouldn't ever drop back down to 0.



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