Fixed #6195 -- Documented caching options for javascript_catalog.

When you need more fine-grained control you may use per-view conditional

processing functions.

.. conditional-decorators:

.. _conditional-decorators:

The ``condition`` decorator

===========================

cases where you really need it (for example, in conjunction with ``ngettext``

to produce proper pluralizations).

Note on performance

-------------------

The :func:`~django.views.i18n.javascript_catalog` view generates the catalog

from ``.mo`` files on every request. Since its output is constant — at least

for a given version of a site — it's a good candidate for caching.

Server-side caching will reduce CPU load. It's easily implemented with the

:func:`~django.views.decorators.cache.cache_page` decorator. To trigger cache

invalidation when your translations change, provide a version-dependant key

prefix, as shown in the example below, or map the view at a version-dependant

URL.

.. code-block:: python

    from django.views.decorators.cache import cache_page

    from django.views.i18n import javascript_catalog

    # The value returned by get_version() must change when translations change.

    @cache_page(86400, key_prefix='js18n-%s' % get_version())

    def cached_javascript_catalog(request, domain='djangojs', packages=None):

        return javascript_catalog(request, domain, packages)

Client-side caching will save bandwidth and make your site load faster. If

you're using ETags (:setting:`USE_ETAGS = True <USE_ETAGS>`), you're already

covered. Otherwise, you can apply :ref:`conditional decorators

<conditional-decorators>`. In the following example, the cache is invalidated

whenever your restart your application server.

.. code-block:: python

    from django.utils import timezone

    from django.views.decorators.http import last_modified

    from django.views.i18n import javascript_catalog

    last_modified_date = timezone.now()

    @last_modified(lambda req, **kw: last_modified_date)

    def cached_javascript_catalog(request, domain='djangojs', packages=None):

        return javascript_catalog(request, domain, packages)

You can even pre-generate the javascript catalog as part of your deployment

procedure and serve it as a static file. This radical technique is implemented

in django-statici18n_.

.. _django-statici18n: http://django-statici18n.readthedocs.org/en/latest/

.. _url-internationalization:

Internationalization: in URL patterns