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WSGI Website

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The ``wsgi_website`` role can be used for setting-up a website powered by Python

on destination machine. The website needs to use the WSGI specification for

making the Python web application(s) available.

This role is normally not supposed to be used directly, but should instead serve

as the basis for writing website-specific roles. Therefore the role is written

in quite generic way, allowing the integrator to write his/her own logic for

deploying the necessary Python applications/packages, while still reusing a

common base and reducing the workload.

The role implements the following:

* Creates a dedicated user/group for running the WSGI application.

* Creates a base directory where the website-specific code and data should be

  stored at.

* Adds nginx to website's group, so nginx could read the necessary files.

* Adds website administrator to website's group, so administrator could manage

  the code and data.

* Installs additional packages required for running the role (as configured).

* Sets-up a dedicated Python virtual environment for website.

* Install Gunicorn in Python virtual environment.

* Installs additional packages required for running the role in Python virtual

  environment (as configured).

* Configures systemd to run the website code (using Gunicorn)

* Configures nginx to serve the website (static files served directly, requests

  passed on to Gunicorn).

The role is implemented with the following layout/logic in mind:

* Website users are named after the ``FQDN`` (fully qualified domain name) of

  website, in format of ``web-ESCAPEDFQDN``, where ``ESCAPEDFQDN`` is equal to

  ``FQDN`` where dots have been replaced by underscores (for example,

  ``web-wiki_example_com``).

* All websites reside within a dedicated sub-directory in ``/var/www``. The

  sub-directory name is equal to the ``FQDN`` used for accessing the

  website. Owner of the directory is set to be the application administrator,

  while group is set to be the website group. Additionally, ``SGID`` bit is set

  on the directory. This allows admin, with correct umask, to create necessary

  files and directories that should be readable (and eventually writeable) by

  the website user (running the WSGI application) without having to become root.

* All files placed in the website directory should be either created there

  directly, or copied to the directory in order to make sure the ``SGID`` gets

  honored. **Do not move the files, the permissions will not be set correctly.**

* Within the website directory, Python virtual environment can be found within

  the ``virtualenv`` sub-directory. The virtual environment is also symlinked to

  website admin's ``~/.virtualenvs/`` directory for easier access (and

  auto-completion with virtualenvwrapper).

* Within the website directory, nginx will expect to find the static files

  within the ``htdocs`` sub-directory (this can be symlink too). Locations/aliases

  can be configured for static file serving.

* Within the website directory, systemd service will expect to find the website

  code within the ``code`` sub-directory (this can be symlink too).

* nginx communicates with WSGI server over a dedicated Unix socket for each

  website.

Parameters

~~~~~~~~~~

**admin** (string, mandatory)

  Name of the operating system user in charge of maintaining the website. This

  user is capable of making modifications to website configuration anda data

  stored within the website directory.

**fqdn** (string, mandatory)

  Fully-qualified domain name where the website is reachable. This value is used

  for calculating the user/group name for dedicated website user, as well as

  home directory of the website user (where data/code should be stored at).

**packages** (list, optional)

  A list of additional packages to install for this particular WSGI

  website. This is usually going to be development libraries for building Python

  packages.

**rewrites** (list, optional)

  A list of rewrite rules that are applied to incoming requests. Each element of

  the list should be a string value compatible with the format of ``nginx``

  option ``rewrite``. The keyword ``rewrite`` itself should be omitted, as well

  as trailing semi-colon (``;``).

**static_locations** (list, optional)

  List of locations that should be treated as static-only, and not processed by

  the WSGI application at all. This is normally used for designating serving of

  static/media files by Nginx (for example, in case of Django projects for

  ``/static/`` and ``/media/``).

**uid** (integer, mandatory)

  UID/GID (they are set-up to be the same) of the dedicated website

  user/group.

**use_paste** (boolean, optional)

  Tell Gunicorn to assume that the passed-in ``wsgi_application`` value is a

  filename of a Python Paste ``ini`` file instead of WSGI application.

**virtuaelnv_packages** (list, optional)

  A list of additional packages to install for this particular PHP

  appliction. This is usually going to be different PHP extensions.

**wsgi_application** (string, mandatory)

  WSGI application that should be started by Gunicorn. The format should be

  conformant to what the ``gunicorn`` command-line tool accepts. If the

  ``use_paste`` option is enabled, the value should be equal to filename of the

  Python Paste ini file, located in the ``code`` sub-directory.

Examples

~~~~~~~~

Here is an example configuration for setting-up a (base) WSGI website (for

running a bare Django project):

.. code-block:: yaml

    ---

    - role: wsgi_website

      admin: admin

      fqdn: django.example.com

      static_locations:

        - /static

        - /media

      uid: 2004

      virtualenv_packages:

        - django

      wsgi_application: django_example_com.wsgi:application