Performance
===========

Wagtail is designed for speed, both in the editor interface and on the front-end, but if you want even better performance or you need to handle very high volumes of traffic, here are some tips on eking out the most from your installation.


Editor interface
~~~~~~~~~~~~~~~~

We have tried to minimise external dependencies for a working installation of Wagtail, in order to make it as simple as possible to get going. However, a number of default settings can be configured for better performance:


Cache
-----

We recommend `Redis <http://redis.io/>`_ as a fast, persistent cache. Install Redis through your package manager (on Debian or Ubuntu: ``sudo apt-get install redis-server``), add ``django-redis-cache`` to your requirements.txt, and enable it as a cache backend::

	CACHES = {
	    'default': {
	        'BACKEND': 'redis_cache.cache.RedisCache',
	        'LOCATION': '127.0.0.1:6379',
	        'OPTIONS': {
	            'CLIENT_CLASS': 'redis_cache.client.DefaultClient',
	        }
	    }
	}

Without a persistent cache, Wagtail will recreate all compressable assets at each server start, e.g. when any files change under ``./manage.py runserver``.


Sending emails in the background using Celery
---------------------------------------------

Various actions in the Wagtail admin backend can trigger notification emails - for example, submitting a page for moderation. In Wagtail's default configuration, these are sent as part of the page request/response cycle, which means that web server threads can get tied up for long periods if many emails are being sent. To avoid this, Wagtail can be configured to do this as a background task, using `Celery <http://www.celeryproject.org/>`_ as a task queue. To install Celery, add ``django-celery`` to your requirements.txt. A sample configuration, using Redis as the queue backend, would look like::

    import djcelery

    djcelery.setup_loader()

    CELERY_SEND_TASK_ERROR_EMAILS = True
    BROKER_URL = 'redis://'

See the Celery documentation for instructions on running the worker process in development or production.


Search
------

Wagtail has strong support for `Elasticsearch <http://www.elasticsearch.org/>`_ - both in the editor interface and for users of your site - but can fall back to a database search if Elasticsearch isn't present. Elasticsearch is faster and more powerful than the Django ORM for text search, so we recommend installing it or using a hosted service like `Searchly <http://www.searchly.com/>`_.


Database
--------

Wagtail is tested on SQLite, and should work on other Django-supported database backends, but we recommend PostgreSQL for production use.


Public users
~~~~~~~~~~~~

Caching proxy
-------------

To support high volumes of traffic with excellent response times, we recommend a caching proxy. Both `Varnish <http://www.varnish-cache.org/>`_ and `Squid <http://www.squid-cache.org/>`_ have been tested in production. Hosted proxies like `Cloudflare <https://www.cloudflare.com/>`_ should also work well.

.. versionadded:: 0.4

    Wagtail supports automatic cache invalidation for Varnish/Squid. See :ref:`frontend_cache_purging` for more information.