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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: Tomcat AJP vs mod_jk's max_pool_size
Date Fri, 23 Jul 2010 08:55:44 GMT
On 23.07.2010 04:07, Imran Khan wrote:
> Hi,
>
> I am currently using apache tomcat 5.5 using mod_jk to connect with apache
> 2.2.
>
> I am curious to understand how the AJP 1.3 connector works. Basically I
> would like to know if maxThreads attribute has the same meaning with the AJP
> connector as it does with standard HTTP connectors. I would like to increase
> the number of connectors, but I noticed there is also connection_pool_size
> and connection_pool_minsize on the workers.properties file.
>
> What is the relationship between the AJP connectors maxThreads and the
> connection_pool_size?

The configuration of the connection pool size in workers.properties is 
per Apache *process*. On most platforms Apache has a dynamically managed 
number of processes, so in total there will be much more connections 
than the configured pool size. Pools are not shared over process 
boundaries. The most notable exception is Windows, since the Apache MPM 
for Windows uses a single process with lots of threads.

mod_jk will automatically detect how many threads per process you have 
and set the pool size to this value, see docs at:

http://tomcat.apache.org/connectors-doc/reference/workers.html

So you should fiddle with the pool size on the mod_jk side only, if you 
want to artificially restrict it. You might want to set the minimum pool 
size though.

For Tomcat the story is different, the max thread pool size is the 
maximum number of threads available to handle connections coming in on 
the respective Connector port. Since AJP uses persistent connections, 
you usually have much more connections, than in-flight requests. The 
numbers get even bigger, if you have a farm of Apache servers in front. 
Each one will consume Tomcat threads.

A good starting point for the mod_jk configuration is the example 
configuration contained in the mod_jk source download for version 
1.2.30. Previous versions do not include a production ready example config.

Regards,

Rainer


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