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Subject: RE: log4j SEVERE ThreadDeath in Tomcat 5.0.25
Date: Thu, 5 Aug 2004 13:23:04 -0400
Message-ID: <9C5166762F311146951505C6790A9CF801FC38E2@US-VS1.corp.mpi.com>
Thread-Topic: log4j SEVERE ThreadDeath in Tomcat 5.0.25
Thread-Index: AcR7D2BaA9hveMHnQGmE5I5c47pSNgAAM74A
From: "Shapira, Yoav" <Yoav.Shapira@mpi.com>
To: "Jakarta Commons Developers List" <commons-dev@jakarta.apache.org>


Hola,

>i'm not sure i understand what ceki's point is. i can't see that he
>gives any reason for pointing the finger in the way he does. maybe if=

>ceki explained how using classloaders as keys effects log4j, i'd see =
a
>bit better...

The issue is:
- Web application deployed on Tomcat uses log4j via commons-logging
- When said application is restarted (using one of the methods provide=
d
by Tomcat do restart a webapp without restarting the Tomcat server
itself), a java.lang.ThreadDeath exception is thrown when
commons-logging calls a log4j logging function.
- We suspect this exception is thrown by Tomcat because the ClassLoade=
r
used by commons-logging to load the log4j class is invalid.  But it's
still the cache key in the commons-logging cache.  It's invalid becaus=
e
when restarting a webapp Tomcat provides it with a new set of
classloaders per the Servlet Specification.

>the commons-logging classloader stuff was created IIRC by craig, remy=

>and others. i don't feel qualified to second-guess their knowledge of=

>servlet containers.

You recall correctly as far as Craig ;)  We're not second-guessing the=
ir
knowledge or even their implementation.  But the Tomcat webapp reloadi=
ng
code has evolved sufficiently since the initial creation of
commons-logging's cache implementation that now the two are not playin=
g
perfectly together.

>i've wanted for a while to use a WeakHashMap so that old classloaders=

>who be garbage collected but don't see that there's an easy way to do=

>this without breaking compatibility.

What would break if we switched commons-logging to use such a
WeakHashMap instead of the currently used normal HashMap?

Yoav


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