Saturday, June 19, 2010

Cherokee Django

The Cherokee Cookbook and Yann Malet's Blog Roll post have pretty helpful directions for setting up the Cherokee webserver with Django. I found it a little tricky to set it up on a virgin Ubuntu Lucid Lynx system, though, so I thought I'd share my steps to get it going:

Install Cherokee and Django

You can get a fairly recent version of each from the Lucid repositories. Because you will compile uWSGI in a sec, you will also need to get python-dev and libxml2-dev:

$ sudo apt-get install cherokee libcherokee-mod-libssl python-django python-dev libxml2-dev

Install uWSGI

According to the cherokee docs, the best way to run django is via uWSGI. On the uwsgi home page, they do have a link to an ubuntu ppa for uwsgi. It looks pretty well maintained, and it's nice of Steve Crozz to maintain it, but I don't feel great about using someone's personal-package archive in a production environment. So I figured I would just get the code and build it myself.

Unfortunately uwsgi doesn't quite have the "forehead install" kind of make file. As I mentioned before, on ubuntu you need the python-dev and libxml2-dev debs, and you also need to specify the version of python you will use it with. These are the exact steps I took:

$ wget -nd -O /tmp/uwsgi.tar.gz $ tar xz -C /tmp -f /tmp/uwsgi.tar.gz $ cd /tmp/uwsgi- $ VERSION_TO_MAKE=`python --version 2>&1 | perl -ne '/(\d)\.(\d)/; print "$1$2"'` $ make -f Makefile.Py$VERSION_TO_MAKE $ sudo mv uwsgi$VERSION_TO_MAKE /usr/local/bin/uwsgi

Create the django_wsgi File

You need to have a wsgi script just like Yann described in his Blog Roll post; since I'm not all that hip to django, though, I didn't know exactly what to call it or where to put it — this is how I eventually ended up organizing my django project:

/srv sites MyProject

That is, I called the wsgi script, and put it in the root of my django project, at the same level as the file. The script contains exactly what Yann described (where MyProject is the name of your project):

import os import django.core.handlers.wsgi # init django settings os.environ['DJANGO_SETTINGS_MODULE'] = 'MyProject.settings' # define wsgi app application = django.core.handlers.wsgi.WSGIHandler() # mount this application at the webroot applications = { '/': 'application' }

Configure Cherokee

Since I'm a complete cherokee noob, the cherokee docs were a little bit thin on this point (the screencast included in the docs might have been exactly what I needed, but I can't stand to sit around and watch screencasts, so I skipped it); this is what you do:

  1. Run the cherokee admin server: $ sudo cherokee-admin
  2. Open up your web browser to and enter the credentials that cherokee-admin spit out.
  3. Click the Virtual Servers navigation link.
  4. Click the Wizards button at the bottom of the virtual servers list.
  5. Select Platforms from the Category list, and click the Run Wizard link next to uWSGI.
  6. On the first page of the wizard, enter the full domain name of your server in the New Host Name (once you get everything working with the new virtual server added by the wizard, you may want to delete it and just re-add the uwsgi handler manually in the default virtual server).
  7. The Document Root field is irrelevant for now; I just set it to my django project's static directory.
  8. For the Configuration File field, enter the path to your wsgi script (you'll change this setting in a sec anyway, so don't sweat it too much), like /srv/sites/MyProject/
  9. For the Same logs as vserver field, I have no idea what this does, so I chose the default.
  10. Click the Submit button to finish the wizard, then go back and click the Information Sources navigation link, and select the new uWSGI 1 source you just created.
  11. The Interpreter field will contain something like this:
    /usr/local/bin/uwsgi -s -t 10 -M -p 1 -C -w /srv/sites/MyProject/
    — change it to this:
    /usr/local/bin/uwsgi -s -t 10 -M -p 1 -C --pythonpath /srv/sites -w MyProject.django_wsgi
    (where /srv/sites is the directory which contains your django project-directory (MyProject), and MyProject is the name of your project).
  12. Save it, and try navigating to your server in a browser.


Getting the right Interperter field setting in cherokee took me a while, and the logs were of no help. What you need to do is just run the uwsgi command (/usr/local/bin/uwsgi ...) yourself in a shell (killing the existing uwsgi instances if necessary); as long as you run it with the same socket as specified in cherokee's Connection field, cherokee will try to use the uwsgi instance you spun up, instead of spinning up its own instance. When you run uwsgi from a shell, you do get all the regular logging and error messages you would expect to see from django (from the shell stdout/stderr).

The other thing I found (which is probably pretty obvious if you know what you're doing) is that I had to give the uwsgi user (by default the same as the cherokee user, www-data) write rights on the django project. So I ended up creating a new copy of the django source from my working copy to /srv/sites/MyProject, and then making www-data the owner of that copy (sudo chown -R www-data:www-data /srv/sites/MyProject). There's probably a better way to do that, but this way worked.

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