#####
Nginx
#####

If you serve Django behind Nginx, then you can delegate the file download
service to Nginx and get increased performance:

* lower resources used by Python/Django workers ;
* faster download.

See `Nginx X-accel documentation`_ for details.


****************************
Configure some download view
****************************

Let's start in the situation described in the :doc:`demo application </demo>`:

* a project "demoproject"
* an application "demoproject.download"
* a :py:class:`django_downloadview.views.ObjectDownloadView` view serves files
  of a "Document" model.

We are to make it more efficient with Nginx.

.. note::

   Examples below are taken from the :doc:`demo project </demo>`.


***********
Write tests
***********

Use :py:func:`django_downloadview.nginx.assert_x_accel_redirect` function as
a shortcut in your tests.

:file:`demo/demoproject/nginx/tests.py`:

.. literalinclude:: ../../demo/demoproject/nginx/tests.py
   :language: python
   :emphasize-lines: 5, 25-34

Right now, this test should fail, since you haven't implemented the view yet.


************
Setup Django
************

At the end of this setup, the test should pass, but you still have to `setup
Nginx`_!

You have two options: global setup with a middleware, or per-view setup with
decorators. 

Global delegation, with XAccelRedirectMiddleware
================================================

If you want to delegate all file downloads to Nginx, then use
:py:class:`django_downloadview.nginx.XAccelRedirectMiddleware`.

Register it in your settings:

.. code-block:: python

   MIDDLEWARE_CLASSES = (
       # ...
       'django_downloadview.nginx.XAccelRedirectMiddleware',
       # ...
   )

Setup the middleware:

.. code-block:: python

   NGINX_DOWNLOAD_MIDDLEWARE_MEDIA_ROOT = MEDIA_ROOT  # Could be elsewhere.
   NGINX_DOWNLOAD_MIDDLEWARE_MEDIA_URL = '/proxied-download'

Optionally fine-tune the middleware. Default values are ``None``, which means
"use Nginx's defaults".

.. code-block:: python

   NGINX_DOWNLOAD_MIDDLEWARE_EXPIRES = False  # Force no expiration.
   NGINX_DOWNLOAD_MIDDLEWARE_WITH_BUFFERING = False  # Force buffering off.
   NGINX_DOWNLOAD_MIDDLEWARE_LIMIT_RATE = False  # Force limit rate off.

Local delegation, with x_accel_redirect decorator
=================================================

If you want to delegate file downloads to Nginx on a per-view basis, then use
:py:func:`django_downloadview.nginx.x_accel_redirect` decorator.

:file:`demo/demoproject/nginx/views.py`:

.. literalinclude:: ../../demo/demoproject/nginx/views.py
   :language: python

And use it in som URL conf, as an example in
:file:`demo/demoproject/nginx/urls.py`:

.. literalinclude:: ../../demo/demoproject/nginx/urls.py
   :language: python

.. note::

   In real life, you'd certainly want to replace the "download_document" view
   instead of registering a new view.


***********
Setup Nginx
***********

See `Nginx X-accel documentation`_ for details.

Here is what you could have in :file:`/etc/nginx/sites-available/default`:

.. code-block:: nginx

   charset utf-8;

   # Django-powered service.
   upstream frontend {
       server 127.0.0.1:8000 fail_timeout=0;
   }

   server {
       listen 80 default;

       # File-download proxy.
       #
       # Will serve /var/www/files/myfile.tar.gz when passed URI
       # like /optimized-download/myfile.tar.gz
       #
       # See http://wiki.nginx.org/X-accel
       # and https://github.com/benoitbryon/django-downloadview
       location /proxied-download {
           internal;
           # Location to files on disk.
           # See Django's settings.NGINX_DOWNLOAD_MIDDLEWARE_MEDIA_ROOT
           alias /var/www/files/;
       } 

       # Proxy to Django-powered frontend.
       location / {
           proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
           proxy_set_header Host $http_host;
           proxy_redirect off;
           proxy_pass http://frontend;
       }
   }

... where specific configuration is the ``location /optimized-download``
section.  

.. note::

   ``/proxied-download`` is not available for the client, i.e. users
   won't be able to download files via ``/optimized-download/<filename>``.

.. warning::

   Make sure Nginx can read the files to download! Check permissions.


*************
Common issues
*************

``Unknown charset "utf-8" to override``
=======================================

Add ``charset utf-8;`` in your nginx configuration file.

``open() "path/to/something" failed (2: No such file or directory)``
====================================================================

Check your ``settings.NGINX_DOWNLOAD_MIDDLEWARE_MEDIA_ROOT`` in Django
configuration VS ``alias`` in nginx configuration: in a standard configuration,
they should be equal.


.. rubric:: References

.. target-notes::

.. _`Nginx X-accel documentation`: http://wiki.nginx.org/X-accel