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From Ruediger Pluem <rpl...@apache.org>
Subject Re: mod_proxy_balancer connection pool limitation problem
Date Sun, 02 Apr 2006 15:31:08 GMT


On 04/02/2006 05:16 PM, Bjørn Stabell wrote:

> 
> <IfModule mpm_worker_module>
>     StartServers          2
>     MaxClients           128
>     MinSpareThreads      25
>     MaxSpareThreads      75
>     ThreadsPerChild      64
>     MaxRequestsPerChild   0
> </IfModule>
> 
> 
> # /nb/apache-2.2/bin/httpd -l
> Compiled in modules:
>   core.c
>   worker.c
>   http_core.c
>   mod_so.c
> 
> 
> This should give 2 processes, each with 64 threads, right?  At the 
> peak, 64 connections are established with the backend:

correct.

> 
> # netstat -an | egrep ":7680.*ESTABLISHED" | wc -l
> 64

Ok, yes there had been some problems with this limit. They should be fixed with 2.2.1.
Could you give the tar ball that Paul rolled a try or wait until the release of 2.2.1?

> 
> 
> Btw, since the number of processes is rather indirect with the advent 
> of mpm-worker, and since most people would be most interested in 
> limiting the total number of connections to the backend (to spare the 
> backend), wouldn't it make more sense to limit the total number?

The total number is actually limited by <maximum number of processes> * <max parameter
for backend>,
but I admit that this should be documented more clearly. And on worker MPM
<maximum number of processes>  <= <MaxClients> / <ThreadsPerChild> +
1.

I guess what you have in mind is a global cache over the different processes.
I think this would require a major refactoring of the proxy code and would make
things more complex and error prone for comparable little gain.

Regards

Rüdiger


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