I've been experiment quite some time with a "typical" django setting upon nginx+apache2+mod_wsgi+memcached(+postgresql) (reading the doc and some questions on SO and SF, see comments)

Since I'm still unsatisfied with the behavior (definitely because of some bad misconfiguration on my part) I would like to know what a good configuration would look like with these hypotesis:

• Quad-Core Xeon 2.8GHz
• 8 gigs memory
• several django projects (anything special related to this?)

These are excerpts form my current confs:

apache2

SetEnv VHOST null 
#WSGIPythonOptimize 2

<VirtualHost *:8082>
    ServerName subdomain.domain.com
    ServerAlias www.domain.com
    SetEnv VHOST subdomain.domain
    AddDefaultCharset UTF-8
    ServerSignature Off

    LogFormat "%{X-Real-IP}i %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" custom
    ErrorLog  /home/project1/var/logs/apache_error.log
    CustomLog /home/project1/var/logs/apache_access.log custom

    AllowEncodedSlashes On

    WSGIDaemonProcess subdomain.domain user=www-data group=www-data threads=25
    WSGIScriptAlias / /home/project1/project/wsgi.py
    WSGIProcessGroup %{ENV:VHOST}
</VirtualHost>

wsgi.py

import os
import sys

# setting all the right paths....


_realpath = os.path.realpath(os.path.dirname(__file__))
_public_html = os.path.normpath(os.path.join(_realpath, '../'))    

sys.path.append(_realpath)
sys.path.append(os.path.normpath(os.path.join(_realpath, 'apps')))
sys.path.append(os.path.normpath(_public_html))
sys.path.append(os.path.normpath(os.path.join(_public_html, 'libs')))
sys.path.append(os.path.normpath(os.path.join(_public_html, 'django')))


os.environ['DJANGO_SETTINGS_MODULE'] = 'settings'

import django.core.handlers.wsgi

_application = django.core.handlers.wsgi.WSGIHandler()

def application(environ, start_response):
    """
    Launches django passing over some environment (domain name) settings
    """

    application_group = environ['mod_wsgi.application_group']
    """
    wsgi application group is required. It's also used to generate the
    HOST.DOMAIN.TLD:PORT parameters to pass over
    """
    assert application_group
    fields = application_group.replace('|', '').split(':')
    server_name = fields[0]
    os.environ['WSGI_APPLICATION_GROUP'] = application_group
    os.environ['WSGI_SERVER_NAME'] = server_name
    if len(fields) > 1 :
        os.environ['WSGI_PORT'] = fields[1]
    splitted = server_name.rsplit('.', 2)    
    assert splitted >= 2
    splited.reverse()
    if len(splitted) > 0 :
        os.environ['WSGI_TLD'] = splitted[0]
    if len(splitted) > 1 :
        os.environ['WSGI_DOMAIN'] = splitted[1]
    if len(splitted) > 2 :
        os.environ['WSGI_HOST'] = splitted[2]
    return _application(environ, start_response)`

folder structure

in case it matters (slightly shortened actually)

/home/www-data/projectN/var/logs
                       /project (contains manage.py, wsgi.py, settings.py)
                       /project/apps (all the project ups are here)
                       /django
                       /libs

Please forgive me in advance if I overlooked something obvious.

My main question is about the apache2 wsgi settings. Are those fine? Is 25 threads an /ok/ number with a quad core for one only django project? Is it still ok with several django projects on different virtual hosts? Should I specify 'process'? Any other directive which I should add? Is there anything really bad in the wsgi.py file?

I've been reading about potential issues with the standard wsgi.py file, should I switch to that?

Or.. should this conf just be running fine, and I should look for issues somewhere else?

So, what do I mean by "unsatisfied": well, I often get quite high CPU WAIT; but what is worse, is that relatively often apache2 gets stuck. It just does not answer anymore, and has to be restarted. I have setup a monit to take care of that, but it ain't a real solution. I have been wondering if it's an issue with the database access (postgresql) under heavy load, but even if it was, why would the apache2 processes get stuck?

Beside these two issues, performance is overall great. I even tried New Relic and got very good average results.