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Posted to users@tomcat.apache.org by Timothy Collett <da...@mac.com> on 2006/11/07 17:32:24 UTC

Webapps inexplicably losing access to common/shared classloaders

Greetings.
I have been having a problem recently with webapps losing access to  
the shared classloader, or, worse, the common classloader.  It  
occurred apparently spontaneously a week ago, and I simply moved to a  
clean Tomcat container of 5.5.20 (I needed to upgrade anyway).  It's  
been working fine since.

However, this morning, one of my webapps cannot see the MySQL JDBC  
jar in the shared classloader...and another cannot see the servlet- 
api jar in the common classloader.  This makes it very difficult to  
actually do anything...

I have not modified either the common/lib, shared/lib, or <webapp>/ 
WEB-INF/lib directories since yesterday, when both these webapps were  
working just fine.  All I've done (that I can tell) is restarted  
Tomcat.  It was similar last week--everything was working OK, and for  
some reason I had to restart Tomcat, and it stopped working (one  
webapp couldn't find javax/servlet/http/HttpServlet).

I would greatly appreciate any help with this.

Timothy Collett

--

With searching comes loss
and the presence of absence:
"My Novel" not found.
~haiku~


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Re: Webapps inexplicably losing access to common/shared classloaders

Posted by David Smith <dn...@cornell.edu>.

Caldarale, Charles R wrote:
>> From: David Smith [mailto:dns4@cornell.edu] 
>> Subject: Re: Webapps inexplicably losing access to 
>> common/shared classloaders
>>
>> Hmmmm..... only fixed by a system restart?  This sounds like an 
>> environment variable is changed during start or stop and the 
>> new value is bad.  Your start and stop scripts aren't attempting
>> to set classpath or something evil like that are they?
>>     
>
> Can't be that specifically, since the CLASSPATH environment variable
> isn't used by the JVM proper, just the launcher in the absence of the
> -cp parameter.  Probably not any other environment variables, since
> (AFAIK) Tomcat's classloaders don't look at any.  However, it might be
> interesting to compare the system properties visible to Tomcat after a
> reboot with those after a Tomcat restart.  The LambdaProbe add-on can
> display them, for example.  Turning on -verbose:class might also provide
> some hints, but it will produce a lot of output.
>
>  - Chuck
>
>   
I'd agree in 99.999% of all cases, but there is always that 0.001% case 
to really throw a monkey wrench in the works.  And I think we are 
looking at it.  It might be worthwhile for testing to simply add some 
echo statements to the start and stop scripts to see what the 
environment looks at those moments.

--David

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RE: Webapps inexplicably losing access to common/shared classloaders

Posted by "Caldarale, Charles R" <Ch...@unisys.com>.

> From: David Smith [mailto:dns4@cornell.edu] 
> Subject: Re: Webapps inexplicably losing access to 
> common/shared classloaders
> 
> Hmmmm..... only fixed by a system restart?  This sounds like an 
> environment variable is changed during start or stop and the 
> new value is bad.  Your start and stop scripts aren't attempting
> to set classpath or something evil like that are they?

Can't be that specifically, since the CLASSPATH environment variable
isn't used by the JVM proper, just the launcher in the absence of the
-cp parameter.  Probably not any other environment variables, since
(AFAIK) Tomcat's classloaders don't look at any.  However, it might be
interesting to compare the system properties visible to Tomcat after a
reboot with those after a Tomcat restart.  The LambdaProbe add-on can
display them, for example.  Turning on -verbose:class might also provide
some hints, but it will produce a lot of output.

 - Chuck


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