Debian – What values to set for Apache 2 worker server pool management

apache-2.2configurationdebianmpm-workerperformance

I recently switched from Apache 2.2 prefork to Apache 2.2 worker, but I have no idea what would be a great MPM config to start with. On prefork, I used :
MaxClients 256
StartServers 190
MinSpareServers 160
MaxSpareServers 220

I'd like to be able to accept at least as much simultaneous requests (190)

Thanks !

PS: Server environment: Debian 5.0, 2x 3.00 Ghz, 4 GB RAM, dedicated to Apache.

Best Answer

ServerLimit 256
MaxClients 256
StartServers 19
ThreadsPerChild 10
MinSpareThreads 160
MaxSpareThreads 220
MaxRequestsPerChild 10000

This will:

Start 190 threads when httpd starts
Serve up to 256 simultaneous requests
Ensure a min of 160 spare threads
Limit a max of 220 spare threads
Limit each httpd child process to serving 10,000 requests before replacing it with a new child process. This helps prevent hanging up the apache server in case there are memory leaks in the underlying application.

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Linux – Fine tunning of Apache 2 MPM Prefork module parameters

You are going to run out of ram before you will be able to server a Million requests. How large are you apache client processes? I bet over 10MB (probably 25MB). You server could probably only handle 250 clients if the clients were only 10MB.

Might try lighttpd with fast-cgi.

To answer you question you would need to edit the mpm.conf files /etc/apache2/modules.d/00_mpm.conf for me, but im on gentoo so it will be a bit diffrent depending on the distro of linux you are using. But in that config there is a secion for prefork

Here is mine for a server with 12Gb of ram. (and we load balance the sites of 20 identical servers)

<IfModule mpm_prefork_module>
        StartServers            100
        MinSpareServers          5
        MaxSpareServers         200
        ServerLimit             375
        MaxClients              375
        MaxRequestsPerChild      0
</IfModule>

VPS hosting is very slow. What’s the bottleneck

Make certain you are not regularly accessing swap space for anything - disk I/O is a very common bottleneck, particularly on Xen VPS' with relatively small RAM allocations (assuming you're at Slicehost, given your mention of using a "slice").

While having swap space seems like a plus (particularly because your VPS doesn't sputter and die when you try to run multiple memory-hungry applications like Apache w/dynamic PHP content and MySQL) it will quickly lead to substandard performance, particularly if you're on a VPS host node full of others doing the same thing.

Edit: I would highly recommend the LowEndBox Wiki (LowEndBox focuses upon virtual environments with memory allocations in the same neighborhood as your own) for optimization tips to get Apache and MySQL running smoothly within your virtual environment.

Best Answer

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Linux – Fine tunning of Apache 2 MPM Prefork module parameters

VPS hosting is very slow. What’s the bottleneck

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