Re: [Jetty-support] ConcurrentModificationExceptions in AbstractSessionManager (Jetty 6.1.5)

[Jan B. <ja...@we...>]

Hi Silvio,

I can't imagine that a concurrent modification exception is ever a good thing,
so it would be nice to track it down :-) It looks like the scavenger for expired
sessions was trying to remove some sessions when maybe a new session was being
inserted into the list. Looks like a synchronisation problem.

However, the trace is not a lot of help because it looks more like a trace from 6.1.2 - 
we haven't had a SessionScavenger thread since then (got replaced with a TimerTask
instead). 

The code has been worked on quite a bit since 6.1.2, so if you see the exception again 
with 6.1.5 or 6.1.6, then please post again (or raise a bug) and we'll investigate.

cheers
Jan


Silvio Bierman wrote:
> Hello all,
> 
> I have seen these periodically in my system logs during the last two 
> years. I am sure they where there when we used to run on Jetty5 but they 
> still exist.
> 
> Does anyone else see these? I have never experienced erratic server 
> behavior related to these exceptions so I guess they are not a real problem?
> 
> Kind regards,
> 
> Silvio Bierman
> 
> 
> 2007-10-15 19:45:59.075::WARN:  EXCEPTION
> java.util.ConcurrentModificationException
>        at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
>        at java.util.HashMap$KeyIterator.next(Unknown Source)
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager$Session.invalidate(AbstractSessionManager.java:914) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager.scavenge(AbstractSessionManager.java:468) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager.access$600(AbstractSessionManager.java:62) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager$SessionScavenger.run(AbstractSessionManager.java:1084) 
> 
>        at 
> org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:475) 
> 
> 2007-10-15 19:46:59.440::WARN:  EXCEPTION
> java.util.ConcurrentModificationException
>        at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
>        at java.util.HashMap$KeyIterator.next(Unknown Source)
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager$Session.invalidate(AbstractSessionManager.java:914) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager.scavenge(AbstractSessionManager.java:468) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager.access$600(AbstractSessionManager.java:62) 
> 
>        at 
> org.mortbay.jetty.servlet.AbstractSessionManager$SessionScavenger.run(AbstractSessionManager.java:1084) 
> 
>        at 
> org.mortbay.thread.BoundedThreadPool$PoolThread.run(BoundedThreadPool.java:475) 
> 
> 
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-- 
Jan Bartel, Webtide LLC | ja...@we... | http://www.webtide.com