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From Skye Poier Nott <s...@F4.ca>
Subject mod_proxy performance with apache 2.2
Date Thu, 20 Mar 2008 19:56:08 GMT
(Moved from users@ list as recommended)

Hi,

I am doing some load testing on a reverse proxy with apache 2.2 +  
mod_proxy (no caching) and I'm getting terrible throughput, I was  
wondering if anyone had a suggestion.

I have the following test network, all on gigabit ethernet:

1 origin server -> 2 mod_proxy servers -> 4 client simulators (flood)  
doing round-robin on the proxies

The origin and proxy servers are configured with name-based virtual  
hosts, the proxy servers with config containing 100 of these:

<VirtualHost *:80>
        ServerName w0099.example.com
        ProxyPass / http://10.100.10.XX:80/w0099/
        ProxyPassReverse / http://10.100.10.XX:80/w0099/
</VirtualHost>

When I start up flood on the client simulators (250 clients each), I  
only get about 4 Mbit/sec out of the origin server!  I've tried  
twiddling all the settings in mod_proxy to no avail (like smax=64  
max=512 ttl=120 min=8 acquire=1)

If I set up lighttpd+proxy on the proxy servers instead of apache, I  
fully saturate the gigE on the origin server (~500 Mbit/sec) as  
expected.

I've tried changing MaxClients from 256 to 512 to 1024, no effect.
I've tried changing from MPM prefork to worker, and twiddled threads  
per child, no effect.

What could explain this 125x difference in performance?  Is there some  
sort of resource or lock or something contention in mod_proxy that I  
should know about?

Are the virtual host lookups taking too long?  Eventually I'd like to  
support up to 10,000 virtual hosts through this proxy.  Is there  
something like mod_vhost_alias for proxy for large configurations?

Is using subdirectories in ProxyPass slowing things down?  Really, I'd  
just like to forward all requests for anything to the origin server IP  
and let the origin worry about serving the right vhost's files.

Thanks,
Skye


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