mod_jk 1.2.6 and hung tomcat

[Mike Charnoky <no...@nextbus.com>]

Hello,

I have been searching through the archives for references to an apparently 
common "hung tomcat problem".  We have been encountering this with our tomcat 
installation (tomcat 4.1.24 / apache 1.3.27 / mod_jk 1.2.4) and I am trying to 
piece together more information on how to fix it.

It seems that work is being done in the upcoming mod_jk 1.2.6 to address this 
issue... the Tomcat "Workers HowTo" document 
(http://jakarta.apache.org/tomcat/tomcat-4.1-doc/jk2/jk/workershowto.html) lists 
several parameters that have been added specifically to deal with this issue.

Is there a concise reference for this problem?  It is intrinsically a tomcat 
issue or is it a problem with a badly behaved app?  How can I determine what is 
causing the hang?  Is there something in the archives that I am completely missing?

Also: Any news on when mod_jk 1.2.6 will be available?  Are the new config 
parameters merely a band-aid or a real solution?


Thanks,

Mike

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Re: mod_jk 1.2.6 and hung tomcat

[David Rees <dr...@greenhydrant.com>]

Mike Charnoky wrote:
>
> Is there a concise reference for this problem?  It is intrinsically a
>  tomcat issue or is it a problem with a badly behaved app?  How can I
> determine what is causing the hang?  Is there something in the
> archives that I am completely missing?

In my case, Tomcat hangs were caused by JVM problems and not related to
Tomcat itself.  This and badly behaved apps causing OOM conditions are
probably the most common failure modes.

The new code in the JK connectors allow mod_jk to "ping" Tomcat with a
short timeout before sending a request there to determine if Tomcat is
alive or not.  This is useful when you have multiple Tomcats running, not
quite as useful if you only have one Tomcat running but will keep Apache
processes from waiting around forever for a response from a hung Tomcat.

> Also: Any news on when mod_jk 1.2.6 will be available?  Are the new
> config parameters merely a band-aid or a real solution?

Last I heard, the next release of mod_jk will be worked on after the JK
developers have released the next version of mod_jk2.  This should happen
in the next few weeks.  It is a real solution, not a band-aid.

-Dave

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