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From Christian Wittwer <wittwe...@gmail.com>
Subject [users@httpd] How much backend connections with mod_proxy and multiple VirtualHost
Date Tue, 07 Sep 2010 06:04:57 GMT
Hi,
We're currently using a setup with a tomcat application server and an
apache in front. The configuration looked like this.
Apache/2.2.3 with prefork model and 7 virtualhosts. Each virtualhost
had the following proxypass to the tomcat ajp connector.

ProxyPass / ajp://localhost:8009/

Now we changed the setup a bit and encountered massive problems. The
configuration now looks like this.
Apache/2.2.3 with prefork model and 40 virtualhosts. Each virtualhost
has the same proxypass as defined above.

After running this setup for some hours, we saw a lot of the following
messages in the apache error_log.

[Wed Aug 25 07:41:48 2010] [error] (70007)The timeout specified has
expired: ajp_ilink_receive() can't receive header
[Wed Aug 25 07:41:48 2010] [error] ajp_read_header: ajp_ilink_receive failed
[Wed Aug 25 07:41:48 2010] [error] (120006)APR does not understand
this error code: proxy: read response failed from (null) (localhost)

I guess it's somehow related to the topic, how much backend
connections mod_proxy opens. I know I can limit the connections using
max, smax (http://httpd.apache.org/docs/current/mod/mod_proxy.html#proxypass).
But how do I calculate that?
I have a ServerLimit of 1024. Does this mean that apache opens 1024 x
40 (virtualhosts, each has a proxypass) = 40960 connections to my
tomcat?

Regards,
Christian

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