Alternative frontends for development

Alternative frontend: mod_python

Virtualenv can 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.

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
   

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 especially there is one major advantage: It can quite easily be set up to auto-reload on code changes.

1. Update a default TracModWsgi setup to make a daemonised 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
         # GLOBAL should generally be used instead of SERVER, see http://code.google.com/p/modwsgi/wiki/IntegrationWithTrac
         WSGIApplicationGroup %{GLOBAL}
         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>
   

2. Go to ​ReloadingSourceCode and save the Python script as /path/to/my/virtualenv/bin/monitor.py
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