Python Rendertron

Rendertron middleware for Python applications.

Rendertron is a headless Chrome rendering solution designed to render & serialise web pages on the fly. The goal of this package is to provide middleware to render a request using a Rendertron service and make the result available.

This makes it possible to for example render Progressive Web Apps (PWA), wait for it to fully render (completes initial data loading etc.) and use that fully built markup as a response.

Besides the fact that your user will see a fully rendered application faster it also allows search engines to properly index the markup.

Installing

Install a Rendertron service by following the steps in the documentation.

Install this package using pip:

pip install rendertron

You can also install the latest development version using pip's -e flag:

pip install -e git://git@github.com:frontendr/python-rendertron.git@develop#egg=rendertron

This will install the develop branch.

Django

First, add 'rendertron' to the INSTALLED_APPS list in settings.

Then you have 2 choices:

• Enable the middleware and render everything that matches either RENDERTRON_INCLUDE_PATTERNS or does not matches anything in RENDERTRON_EXCLUDE_PATTERNS. See the Configuration section for more information about those.
• Decorate specific views with the @rendertron_render decorator to only let render those views with the Rendertron service.

Middleware

1. Add 'rendertron.middleware.DjangoRendertronMiddleware' to the MIDDLEWARE list in the settings.
2. Make sure to specify either RENDERTRON_INCLUDE_PATTERNS to specify path patterns which are to be rendered by the Rendertron service or RENDERTRON_EXCLUDE_PATTERNS_EXTRA to only specify what to exclude.

Decorate specific views

Instead of relying on the middleware and settings it is also possible to decorate specific views with the @rendertron_render decorator.

from rendertron.decorators.django import rendertron_render


@rendertron_render
def my_view(request):
    ...

For class based views use Django's method_decorator.

from django.utils.decorators import method_decorator
from django.views.generic import TemplateView

from rendertron.decorators.django import rendertron_render


@method_decorator(rendertron_render, name="dispatch")
class MyView(TemplateView):
    ...

Configuration

Most configuration is done by specifying specific variables. For Django users that's done in your site's settings.

The following settings are available:

Setting	Default	Description
RENDERTRON_BASE_URL	'http://localhost:3000/'	The url the Rendertron service is listening on.
RENDERTRON_RENDER_QUERY_PARAM	'rendertron_render'	The query parameter added to the request url passed to Rendertron. This is used to differentiate normal requests with requests from Rendertron.
RENDERTRON_STORAGE	See Storage	An object literal specifying and configuring the storage class to be used. See the Storage section for more information.
RENDERTRON_INCLUDE_PATTERNS	[]	A list of regular expression patterns to include. Once a pattern in this list matches the request no further checking will be done.
RENDERTRON_EXCLUDE_PATTERNS	List of common extensions.	By default this is a list of common static file type extensions used on the web. If Django is detected it's STATIC_URL and MEDIA_URL paths are added to the list. Note that if you override this setting all defaults are gone. If you want to keep these defaults and add your own patterns use RENDERTRON_EXCLUDE_PATTERNS_EXTRA.
RENDERTRON_EXCLUDE_PATTERNS_EXTRA	[]	Like RENDERTRON_EXCLUDE_PATTERNS but will be appended to that list.

Storage

Storage classes are handling the logic of storing the results coming from the Rendertron service for a period of time. They handle if, how, where and how long a result is stored. There are some core storage classes available the system is built for it to be very easy to built your own.

The choice of one of the built in storage classes depends on your framework.

Any framework: DummyStorage

A storage class that doesn't do anything. It doesn't store and will never return a stored result.

To use it simply set RENDERTRON_STORAGE['CLASS'] to 'rendertron.storage.DummyStorage'. It has no options.

Django: DjangoCacheStorage

A storage class that utilizes Django's cache framework to store the results.

To use it simply set RENDERTRON_STORAGE['CLASS'] to 'rendertron.storage.DjangoCacheStorage'. It has the following options:

Setting	Default	Description
TIMEOUT	Django's DEFAULT_TIMEOUT cache setting which is 300 (5 minutes)	The number of seconds the result should be stored in the cache. It's the timeout argument for Django's cache.set method.
VERSION	None	The version argument which is passed to Django's cache.set method.

Example config:

RENDERTRON_STORAGE = {
    'CLASS': 'rendertron.storage.DjangoCacheStorage',
    'OPTIONS': {
        'TIMEOUT': 300,
    }
}

Running tests

First install Django to be able to test Django related things.

pip install django

Then run the tests via django-admin using the provided minimal settings file.

django-admin test --pythonpath . --settings tests.django.settings

License

MIT