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Making Django REST Framework reactive

Project description

This package enables regular Django REST Framework views to become reactive, that is so that client-side applications may get notified of changes to the underlying data as soon as they happen, without the need to poll the API again. While the initial request is done as a regular HTTP request, all the update notifications come through WebSockets.

Install

Prerequisites

The reactive extensions for Django REST Framework currently require the use of django-websocket-redis for push notifications. When Channels get merged into Django mainline, we will probably migrate to using those.

From PyPI

pip install djangorestframework-reactive

From source

pip install https://github.com/genialis/django-rest-framework-reactive/archive/<git-tree-ish>.tar.gz

where <git-tree-ish> can represent any commit SHA, branch name, tag name, etc. in DRF Reactive’s GitHub repository. For example, to install the latest version from the master branch, use:

pip install https://github.com/genialis/django-rest-framework-reactive/archive/master.tar.gz

Configure

There are several things that need to be configured in the Django settings file:

  • rest_framework_reactive needs to be added to INSTALLED_APPS.

  • DEFAULT_PAGINATION_CLASS needs to be set to rest_framework_reactive.pagination.LimitOffsetPagination (optionally, this pagination class can instead be set for all viewsets configured for reactivity).

  • WS4REDIS_SUBSCRIBER needs to be set to rest_framework_reactive.websockets.QueryObserverSubscriber.

  • DJANGO_REST_FRAMEWORK_REACTIVE needs to be configured with hostname and port where the internal RPC will live. It should be set to something like:

    DJANGO_REST_FRAMEWORK_REACTIVE = {
       'host': 'localhost',
       'port': 9432,
    }

    The hostname and port must be such that they are reachable from the Django application server.

Each ViewSet that should support reactivity, must be registered by using:

from rest_framework_reactive.pool import pool
pool.register_viewset(MyViewSet)

The best place to do this is inside models.py or better, inside the ready handler of an AppConfig.

At the moment, you are required to change your project’s manage.py to monkey patch the runobservers command with support for gevent coroutines. Note that regular Django application server still runs as normal, only the observer process runs using coroutines.

The modified manage.py should look as follows:

#!/usr/bin/env python
import os
import sys

if __name__ == "__main__":
    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "genesis.settings.development")

    # This is needed here so the monkey patching is done before Django ORM is loaded. If we
    # do it inside the 'runobservers' management command, it is already too late as a database
    # connection has already been created using thread identifiers, which become invalid
    # after monkey patching.
    if 'runobservers' in sys.argv:
        import gevent.monkey
        import psycogreen.gevent

        # Patch the I/O primitives and psycopg2 database driver to be greenlet-enabled.
        gevent.monkey.patch_all()
        psycogreen.gevent.patch_psycopg()

    from django.core.management import execute_from_command_line

    execute_from_command_line(sys.argv)

And finally, urls.py need to be updated to include some additional paths:

urlpatterns = [
  # ...
  url(r'^api/queryobserver/', include('rest_framework_reactive.api_urls')),
  # ...
]

Run

In addition to running a Django application server instance, you need to also run a separate observer process. You may start it by running:

python manage.py runobservers

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