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From Ramblewski David <David.Ramblew...@atosorigin.com>
Subject RE: connection_pool_size informations
Date Thu, 01 Apr 2010 13:56:25 GMT
Hi,

Does anyone can help me know what exactly impact the "connection_pool_size" parameter in mod_jk
configuration file?
If I've posted to the wrong mailing list, please let me know the right one.

Thanks for help,

David

-----Message d'origine-----
De : Ramblewski David
Envoyé : mercredi 31 mars 2010 10:29
À : 'users@tomcat.apache.org'
Objet : connection_pool_size informations


Hi,

I'm actually working on a production platform to make some benchmarks and there is an important
latency mainly because of sockets renewal.

The platform is set up with 4 front servers hosting 1 apache process and 24 middle servers
hosting 4 tomcat instances.
Thus there is 4 apaches and 96 tomcat workers in the mod_jk worker configuration file.

The previous apache non working configuration was:

<IfModule worker.c>
StartServers        5
MaxClients          8192
ServerLimit         137
MinSpareThreads     25
MaxSpareThreads     60
ThreadsPerChild     60
MaxRequestsPerChild 1000
</IfModule>


I found an apache MPM worker configuration which has successfully passed the benchmarks:

<IfModule worker.c>
StartServers        16
MaxClients          8192
ServerLimit         34
MinSpareThreads     25
MaxSpareThreads     150
ThreadsPerChild     256
MaxRequestsPerChild 0
</IfModule>


Reading the tomcat worker documentation, I saw that the connection_pool_size parameter is
equal to ThreadsPerChild by default.
This defines the number of connections made to the AJP backend that are maintained as a connection
pool. It will limit the number of those connection that each web server child process can
made.

So I first conclude that:
1 Apache Child process = 1 mod_jk connection pool shared between N threads
and connection_pool_size = N where N is the value of ThreadsPerChild apache parameter

Thus in the example above we could have maximum 34 mod_jk connection pools (1 per Apache child)
and connection_pool_size = 256 -> 8704 connections


But I found the configuration site below:

http://lbconfig.appspot.com/?lb=mod_jk&v=1.2.27%20or%20less&nca=4&ncj=4&nai=4&nji=24&njips=4&f=true&c=false&lr=false&lrl=&mpm=Worker

which explain us that there is a connection_pool_size for each worker.
Thus 1 Apache Child process can handle X threads and indirectly Y workers so there is Y mod_jk
connection pools per apache child and connection_pool_size = X.

Thus in the example above we could have maximum 34 (ServerLimit) * 96 (tomcat workers) mod_jk
connection pools and connection_pool_size = 256 -> 835584 connections

Does anyone can elucidate that question?
Apache ThreadPerChild parameter should be superior or equal to the number of mod_jk tomcat
workers?

Thanks for help,

David Ramblewski



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