Alternative frontends

Alternative frontend: mod_python

Virtualenv can also be used with Apache and mod_python, but as mod_python will be a system install it will not be aware of the virtualenv without some configuration. For development this is useful as one Apache can serve various development versions in a more permanent way. This method will use the system Python, but will add the libraries from the virtualenv.

Step 1: Make a new frontend script that for instance can be stored in the virtualenv 'bin' directory.

#myvirtualtrac.py

import os
import site
site.addsitedir('/path/to/my/virtualenv/lib/python2.4/site-packages')

from trac.web.modpython_frontend import handler

Step 2: Update Apache config to use this script - add or update options according to the default mod_python setup like for instance found in TracModPython.

# Extend the path so Apache will find your script on path
PythonPath "['/path/to/my/virtualenv/bin'] + sys.path"

# Make mod_python use new frontend instead of trac.web.modpython_frontend
PythonHandler myvirtualtrac

Alternative frontend: mod_wsgi

Using Apache, mod_wsgi is a very good alternative to mod_python. Setting this up follows the same pattern, but for development escpecially there is one major advantage: It can quite easily be set up to auto-reload on code changes.

Step 1: Update a default TracModWsgi setup to make a deamonised process, and as of mod_wsgi 2.0 (this setup depends on ≥ 2.0) there is built-in support for custom paths and similar. Example of a full VirtualHost configuration:

<VirtualHost *:80>
    ServerName virtualtrac.local

    # Update user and group to be whatever on your system is intended to run the deamon
    # Update the paths to point to virtualenv site-packages (for trac+++) and bin (for script)
    WSGIDaemonProcess virtualtrac user=www group=www threads=25 python-path=/path/to/my/virtualenv/lib/python2.4/site-packages:/path/to/my/virtualenv/bin

    WSGIScriptAlias / /path/to/my/virtualenv/bin/virtualtrac.wsgi

    <Location />
      WSGIReloadMechanism Process
      WSGIProcessGroup virtualtrac
      WSGIApplicationGroup %{SERVER}
      Order deny,allow
      Allow from all
    </Location>

    # Authentication
    <LocationMatch (/[^/.]+/login)>
      # Note: Change settings with regards to auth method, paths and domain
      AuthType Digest
      AuthName "virtualtrac"
      AuthDigestDomain /trac http://virtualtrac.local
      AuthDigestProvider file
      AuthUserFile /path/to/access.htdigest
      Require valid-user
    </LocationMatch>

</VirtualHost>

Step 2: Go to ​http://code.google.com/p/modwsgi/wiki/ReloadingSourceCode and save the long Python script that follows the text 'Example code for such an automatic restart mechanism…'. Save it as /path/to/my/virtualenv/bin/monitor.py

Step 3: A basic WSGI frontend script, save as /path/to/my/virtualenv/bin/virtualtrac.wsgi

import sys
sys.stdout = sys.stderr

import os
os.environ['TRAC_ENV_DIR'] = "/path/to/trac/project"
# or, alternatively for multiple projects
#os.environ['TRAC_ENV_PARENT_DIR'] = "/parent/path/to/many/projects"
os.environ['PYTHON_EGG_CACHE'] = '/path/to/a/temp/to/cache/eggs'

import trac.web.main

import monitor
monitor.start(interval=1.0)
# Additionally monitor easy-install.pth to restart whenever installs are done
monitor.track('/path/to/my/virtualenv/lib/python2.4/site-packages/easy-install.pth')

application = trac.web.main.dispatch_request