SLP: Django: Deployment

Go up to the main SLP documents page (md)

This page is for how to deploy your Django apps on an Ubuntu server -- specifically, Ubuntu 14.04. This is not needed for your local development, as you can run python manage.py runserver to test it out locally, or test it out on the course server provided. However, if you do want to get it running through Apache, read on...

Installing packages

To install Django on your own system, under Ubuntu 14.04, just enter sudo apt-get install python-django python-mysqldb, and it will do the rest. As of the writing of this tutorial (Aug 31, 2014), this installs Python version 2.7.6 and Django version 1.6.1.

About installing the wsgi module, and for python 2/3...

Configuring Apache

This assumes Apache version 2.4; if you are using version 2.2, then the syntax for this is quite different (some of those differences are described below).

This part specifically deals with configuring multiple django apps on the same web server, as that is what is needed for this course. For each django app, the following 8 lines need to be added to /etc/apache2/sites-available/000-default.conf, right above the end </VirtualHost> line:

Alias /django/user/static /home/slp/user/mysite/static
<Directory /home/slp/user/mysite/static>
  Require all granted
</Directory>
WSGIScriptAlias /django/user /home/slp/user/mysite/mysite/wsgi.py
WSGIDaemonProcess user python-path=/home/slp/user/mysite
<Location /django/user>
  WSGIProcessGroup user
</Location>
<Directory /home/slp/user/mysite/mysite>
  <Files wsgi.py>
    Require all granted
  </Files>
</Directory>

A bunch of notes:

user is the username of whomever is running the Django app, and mysite is the name of the project.
The first four lines deal with the static directory -- since there are multiple Django apps, there will be multiple static directories. See the Django getting started (md) page for how to configure a given Django project to use the correct static directory. Using a static directory that is directly below the main project directory (as opposed to in an app directory) will likely require one to run python manage.py collectstatic, as described on the Django getting started (md) page.
The WSGIScriptAlias line indicates the URL (after the server) links to the particular Django app. As we want them in sub-directories, we have the URL part be /django/user. Note that we do not have to create the /django/ directory in the HTML document root (likely /var/www/html).
The WSGIProcessGroup creates a process group, which allows one (or more) apps to run as a specific user. The user part of that line needs to be a valid user name on the system
The WSGIDaemonProcess line indicates that this particular Django app will run under the user user, and the path to the django app is provided. The user part of that line needs to match the one in the WSGIProcessGroup.
The Require all granted line allows the viewing of the Django app. If you are using Apache 2.2 (or earlier), replace Require all granted with two lines: Order deny,allow and then Allow from all.
If using virtualenv, such as described in the Python's virtualenv setup (md) page, then the WSGIDaemonProcess line will differ, and will look like: WSGIDaemonProcess user python-path=/home/slp/user/mysite python-home=/path/to/virtualenv/lib/python3.5/site-packages
Note that the virtualenv directory should end in lib/python3.5/site-packages
The wsgi-admin.cpp program, described below, creates this with the -path flag

Sine there are going to be many users in a system, it will be easier to put this in a separate file (say, called /etc/apache2/django.conf), and insert a Include django.conf line in /etc/apache2/sites-available/000-default.conf (also right above the </VirtualHost> line).

If you are enabling these through SSL, there is a slight change. When Apache restarts (or reloads), the default (i.e., non-SSL) site is brought up first, followed by the SSL site. As the daemon process has already been declared in 000-default.conf (for the non-SSL site), it will cause an error to declare it again for the SSL site. Thus, the SSL version should not have the WSGIDaemonProcess line; all the other lines remain the same. This implies that the file included from default-ssl.conf will be a different one than the one included from 000-default.ssl.

Managing multiple users

The issue with the WSGI module is that if any one of the WSGI files it is configured with does not exist, then all of the WSGI modules don't work. This means you can't pre-generate the list of WSGI links for a class, as none of them will work until everybody has it set up, which is not viable.

To work around this, you can see the wsgi-admin.cpp (src), which will allow students to register and remove their WSGI apps. It will update the necessary Apache configuration files, and then reload the web server. It can also be used just to do the regeneration and reloading -- and if a file is not found (or is not valid), then it is excluded from the configuration files. Installation is tricky, but the process is described in the comments at the top of that file. The directions for how to use it can be found on the Django getting started (md) page.