Load testing with Tomcat 5.5, Apache 2.2 and mod_proxy_ajp

[Ian Shafer <ia...@1321.org>]

Hello,

I'm currently load testing a webapp running on Tomcat 5.5 that is  
fronted by Apache 2.2 and uses mod_proxy_ajp to communicate between  
the two.

I'm seeing some odd behavior that I cannot explain.

I have this line in my httpd.conf file:

ProxyPass /webapp/ ajp://localhost:8009/webapp/ min=256 max=256

and in tomcat I have maxThreads set to 256 for both my HTTP connector  
and my AJP connector.  For some reason, though, I still get a message  
in my tomcat log saying:

ERROR TP-Processor4 org.apache.tomcat.util.threads.ThreadPool - All  
threads (256) are currently busy, waiting. Increase maxThreads (256)  
or check the servlet status


Why does this happen? I thought my 'max=256' setting in httpd.conf  
would only 256 connections at once.

Also, if anyone has any experience with setting up Apache and Tomcat  
for very high performance, I would appreciate any pointers.

Thanks,

Ian


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Re: Load testing with Tomcat 5.5, Apache 2.2 and mod_proxy_ajp

[Mladen Turk <ml...@jboss.com>]

Ian Shafer wrote:
> Hello,
> 
> I have this line in my httpd.conf file:
> 
> ProxyPass /webapp/ ajp://localhost:8009/webapp/ min=256 max=256
> 
> and in tomcat I have maxThreads set to 256 for both my HTTP connector 
> and my AJP connector.  For some reason, though, I still get a message in 
> my tomcat log saying:
> 
> ERROR TP-Processor4 org.apache.tomcat.util.threads.ThreadPool - All 
> threads (256) are currently busy, waiting. Increase maxThreads (256) or 
> check the servlet status
> 
> 
> Why does this happen? I thought my 'max=256' setting in httpd.conf would 
> only 256 connections at once.
>

Depends on the mpm you are using. If it's worker mpm, then max=256 means
that it will have max 256 connection per worker, so you can end up with
256*(MaxClients/ThreadsPerChild). If it's prefork mpm, then max=256 is
not used and is always 1. The max number of connections in that case
is MaxClients.

Regards,
Mladen.


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