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From Remy Maucherat <r...@jboss.org>
Subject Re: heavy load - ConcurrentModificationException
Date Thu, 29 Apr 2004 13:28:20 GMT
Gilad Buzi wrote:
> Hello,
> Tomcat 4.1.30
> Under heavy load, we seem to be getting this error every once in a while:
> 
> java.util.ConcurrentModificationException
> at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:448)
> at java.util.AbstractList$Itr.next(AbstractList.java:419)
> at java.util.AbstractCollection.remove(AbstractCollection.java:254)
> at 
> org.apache.coyote.RequestGroupInfo.removeRequestProcessor(RequestGroupInfo.java:17) 
> 
> at org.apache.coyote.RequestInfo.setGlobalProcessor(RequestInfo.java:96)
> at 
> org.apache.coyote.http11.Http11Protocol$MXPoolListener.threadEnd(Http11Protocol.java:620)

> 
> at 
> org.apache.tomcat.util.threads.ThreadPool.removeThread(ThreadPool.java:279)
> at 
> org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:727) 
> 
> at java.lang.Thread.run(Thread.java:534)
> 
> We've narrowed down the problem and it's definitely not in our code.  As 
> the error indicates, it is Tomcat (coyote).  Searching some of the bug 
> databases and this mailing list's archive, I see that this has been 
> around for a while (why don't they just use a synchronized method?!)
> So I'm wondering if anyone knows of the last stable version of Tomcat 
> that doesn't raise this exception under heavy load.
> 
> BTW, we're using the standard connector 
> org.apache.coyote.tomcat4.CoyoteConnector on port 8080 . If we used the 
> other connector, would this go away? 
> (org.apache.ajp.tomcat4.Ajp13Connector for instance)

It would go away, but it would be much much slower (I remember there 
were some benchmarks some time ago, and it wasn't pretty).

You'll have to update from the 4.1.x CVS for the fix, or upgrade to 5.0.19.

-- 
xxxxxxxxxxxxxxxxxxxxxxxxx
Rémy Maucherat
Developer & Consultant
JBoss Group (Europe) SàRL
xxxxxxxxxxxxxxxxxxxxxxxxx

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