Tomcat, out of memory and hot reployment

[Malcolm Warren <ma...@villeinitalia.com>]

Dear All,

I've seen that using hot deploy too often for apps on my production 
server (more than seven or eight times) without restarting Tomcat causes 
an Out of memory exception.
Whereas it doesn't happen on my mac test machine, presumably because it 
has a different jvm from the debian linux production machine.

And I've read in several places the reason for this, for example:
"Hot redeployment always leads to an eventual JVM death as it runs out 
of PermGen memory space that stores class definitions".

What I was wondering is:
If I turn off hot redeployment and use the Tomcat manager to redeploy 
applications, does that solve the problem?
I would assume that it does not, but any information from the experts 
would be very welcome.


Thanks,
Malcolm Warren

RE: Tomcat, out of memory and hot reployment

["Caldarale, Charles R" <Ch...@unisys.com>]

> From: Malcolm Warren [mailto:malcolm@villeinitalia.com]
> Subject: Tomcat, out of memory and hot reployment
> 
> If I turn off hot redeployment and use the Tomcat manager to redeploy
> applications, does that solve the problem?

No, that is a hot redeployment.

> I would assume that it does not, but any information from the experts
> would be very welcome.

Fix your webapp (or libraries that it uses) so that it doesn't hang onto references to objects that it doesn't need.  (Logging packages are infamous for causing this problem.)  Make sure that any ThreadLocal usage is cleaned up at the end of *each* request.  Watch out for anything in a shared library that keeps persistent references to webapp objects.

Use a profiler to find out where the unwanted references to superseded objects come from.

 - Chuck


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Re: Tomcat, out of memory and hot reployment

[Malcolm Warren <ma...@villeinitalia.com>]

Thanks very much for your answers.
My question has been clarified.

Malcolm


Pid ha scritto:
> On 07/12/2009 10:53, Malcolm Warren wrote:
>> Dear All,
>>
>> I've seen that using hot deploy too often for apps on my production
>> server (more than seven or eight times) without restarting Tomcat causes
>> an Out of memory exception.
>> Whereas it doesn't happen on my mac test machine, presumably because it
>> has a different jvm from the debian linux production machine.
>>
>> And I've read in several places the reason for this, for example:
>> "Hot redeployment always leads to an eventual JVM death as it runs out
>> of PermGen memory space that stores class definitions".
>
> Just to clarify, that is not an accurate statement.
>
> Replace "always leads" with "might lead (depending on what your app is 
> doing)", then check the credibility of the source.
>
>
> p
>
>
>> What I was wondering is:
>> If I turn off hot redeployment and use the Tomcat manager to redeploy
>> applications, does that solve the problem?
>> I would assume that it does not, but any information from the experts
>> would be very welcome.
>>
>>
>> Thanks,
>> Malcolm Warren
>>
>
>
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Re: Tomcat, out of memory and hot reployment

[Pid <pi...@pidster.com>]

On 07/12/2009 10:53, Malcolm Warren wrote:
> Dear All,
>
> I've seen that using hot deploy too often for apps on my production
> server (more than seven or eight times) without restarting Tomcat causes
> an Out of memory exception.
> Whereas it doesn't happen on my mac test machine, presumably because it
> has a different jvm from the debian linux production machine.
>
> And I've read in several places the reason for this, for example:
> "Hot redeployment always leads to an eventual JVM death as it runs out
> of PermGen memory space that stores class definitions".

Just to clarify, that is not an accurate statement.

Replace "always leads" with "might lead (depending on what your app is 
doing)", then check the credibility of the source.


p


> What I was wondering is:
> If I turn off hot redeployment and use the Tomcat manager to redeploy
> applications, does that solve the problem?
> I would assume that it does not, but any information from the experts
> would be very welcome.
>
>
> Thanks,
> Malcolm Warren
>


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