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user749618
Asked: 2011-07-25 11:56:00 +0800 CST

Why are there double apache processes for mod_wsgi?

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I am running a Django app using mod_wsgi, and am trying to understand how the apache processes work.

Here is my apache httpd.conf:

<VirtualHost *:80>
    ServerName www.example.com
    ServerAlias example.com

    WSGIDaemonProcess example.com processes=2 threads=15 user=django1 group=django1
    WSGIProcessGroup example.com
    WSGIScriptAlias / /path/to/django.wsgi
</VirtualHost>

I set two processes, but when I look at top, I see two processes under user django1 and two more processes under user www-data:

PID   USER     VIRT RES  COMMAND
14035 django1  524m 350m apache2
14116 django1  499m 326m apache2
11800 root     347m 299m apache2
17486 www-data 347m 292m apache2
17689 www-data 347m 292m apache2

Why are those www-data processes there? Am I running something else and not know it? It seems like they are wasting memory. Only the two apache2 processes for user django1 processes show any CPU load. The www-data users don't have any CPU load.

apache-2.2 mod-wsgi process

1 Answers

  1. Best Answer

    When you use daemon mode and your Django application is therefore running in a separate process to main Apache processes, you still need the Apache parent process and at least one Apache child process. The later is what accepts requests and proxies them through to the mod_wsgi daemon processes. Read:

    http://code.google.com/p/modwsgi/wiki/ProcessesAndThreading

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