[jetty-discuss] [jira] Created: (JETTY-242) NullPointerException on shutdown

[Y. Landrin-S. (JIRA) <ji...@co...>]

NullPointerException on shutdown 
---------------------------------

                 Key: JETTY-242
                 URL: http://jira.codehaus.org/browse/JETTY-242
             Project: Jetty
          Issue Type: Bug
    Affects Versions: 6.1.1rc1
         Environment: Jetty6, two jetty servers started, using SocketConnectors and a BoundedThreadPool with 900 threads.
Platform: WinXP pro, J2SE 6, on a Xeon bi-core
(JVM: -Xmx2048m -Xms256m -Xss256k)
            Reporter: Y. Landrin-Schweitzer
            Priority: Minor


When jetty is asked to shutdown (e.g. ^C in terminal), the shutdown phase is sometimes very long, and accompanied by a NullPointerException in the SessionManager.

This strange bug only happen with a lot of threads, and when they have been really used (test loads around 200 query/s). It does not happen (as far as I have been able to test) in low load situations or with less than 500 threads on my machine.
This is really difficult to reproduce (it happened 6 times, in around 20 or 30 tests).

Note that in the context of my use, the threads have only around 256m of RAM to work, since 1.5g are used by "static" (OldGen) objects. That amounts to less than 512k per thread, but is enough for their normal work.

As this does not really impact the service, I noted this as minor. It may however be the symptom of something major.
Here is the exception trace:

2007-02-22 18:33:18.375::INFO:  Logging to STDERR via org.mortbay.log.StdErrLog
2007-02-22 18:33:18.640::INFO:  jetty-6.1.1rc1
2007-02-22 18:33:18.984::INFO:  Started SocketConnector @ 0.0.0.0:8000
2007-02-22 18:33:18.984::INFO:  jetty-6.1.1rc1
2007-02-22 18:33:19.078::INFO:  Started SocketConnector @ 0.0.0.0:80
2007-02-22 18:41:26.468::INFO:  Shutdown hook executing
2007-02-22 18:44:00.296::WARN:  EXCEPTION
java.lang.NullPointerException
        at org.mortbay.jetty.servlet.HashSessionManager.scavenge(HashSessionManager.java:161)
        at org.mortbay.jetty.servlet.HashSessionManager.access$200(HashSessionManager.java:34)
        at org.mortbay.jetty.servlet.HashSessionManager$SessionScavenger.run(HashSessionManager.java
:290)
        at org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:475)
2007-02-22 18:44:06.390::INFO:  Shutdown hook complete
2007-02-22 18:44:07.531::INFO:  Shutdown hook complete



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