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Build a RESTful API on top of WebSockets using Django channels and Django Rest Framework.

Project description

Note

This repo is cloned from channels-api

Channels API

https://travis-ci.org/linuxlewis/channels-api.svg?branch=master

Channels API exposes a RESTful Streaming API over WebSockets using channels. It provides a ResourceBinding which is comparable to Django Rest Framework’s ModelViewSet. It is based on DRF serializer classes.

It requires Python 3, Django 1.8, and Django Rest Framework 3.0

How does it work?

The API builds on top of channels’ WebsocketBinding class. It works by having the client send a stream and payload parameters. This allows us to route messages to different streams (or resources) for a particular action. So POST /user would have a message that looks like the following

var msg = {
  stream: "users",
  payload: {
    action: "create",
    data: {
      email: "test@example.com",
      password: "password",
    }
  }
}

ws.send(JSON.stringify(msg))

Why?

You’re already using Django Rest Framework and want to expose similar logic over WebSockets.

WebSockets can publish updates to clients without a request. This is helpful when a resource can be edited by multiple users across many platforms.

Getting Started

This tutorial assumes you’re familiar with channels and have completed the Getting Started

  • Add channels_framework to requirements.txt
pip install channels_framework
  • Add channels_framework to INSTALLED_APPS
INSTALLED_APPS = (
    'rest_framework',
    'channels',
    'channels_framework'
)
  • Add a WebsocketDemultiplexer to your channel_routing
# proj/routing.py


from channels.generic.websockets import WebsocketDemultiplexer
from channels.routing import route_class

class APIDemultiplexer(WebsocketDemultiplexer):

    mapping = {
      'questions': 'questions_channel'
    }

channel_routing = [
    route_class(APIDemultiplexer)
]
  • Add your first resource binding
# polls/bindings.py

from channels_framework.bindings import ResourceBinding

from .models import Question
from .serializers import QuestionSerializer

class QuestionBinding(ResourceBinding):

    model = Question
    stream = "questions"
    serializer_class = QuestionSerializer
    queryset = Question.objects.all()


# proj/routing.py

from channels.routing import route_class, route

from polls.bindings import QuestionBinding

channel_routing = [
  route_class(APIDemultiplexer),
  route("question_channel", QuestionBinding.consumer)
]

That’s it. You can now make REST WebSocket requests to the server.

var ws = new WebSocket("ws://" + window.location.host + "/")

ws.onmessage = function(e){
    console.log(e.data)
}

var msg = {
  stream: "questions",
  payload: {
    action: "create",
    data: {
      question_text: "What is your favorite python package?"
    },
    request_id: "some-guid"
  }
}
ws.send(JSON.stringify(msg))
// response
{
  stream: "questions",
  payload: {
    action: "create",
    data: {
      id: "1",
      question_text: "What is your favorite python package"
    }
    errors: [],
    response_status: 200
    request_id: "some-guid"
  }
}
  • Add the channels debugger page (Optional)

This page is helpful to debug API requests from the browser and see the response. It is only designed to be used when DEBUG=TRUE.

# proj/urls.py

from django.conf.urls import include

    urlpatterns = [
        url(r'^channels-api/', include('channels_framework.urls'))
    ]

ResourceBinding

By default the ResourceBinding implements the following REST methods:

  • create
  • retrieve
  • update
  • list
  • delete
  • subscribe

See the test suite for usage examples for each method.

List Pagination

Pagination is handled by django.core.paginator.Paginator

You can configure the DEFAULT_PAGE_SIZE by overriding the settings.

# settings.py

channels_framework = {
  'DEFAULT_PAGE_SIZE': 25
}

Subscriptions

Subscriptions are a way to programmatically receive updates from the server whenever a resource is created, updated, or deleted

By default channels-api has implemented the following subscriptions

  • create a Resource
  • update any Resource
  • update this Resource
  • delete any Resource
  • delete this Resource

To subscribe to a particular event just use the subscribe action with the parameters to filter

// get an event when any question is updated

var msg = {
  stream: "questions",
  payload: {
    action: "subscribe",
    data: {
      action: "update"
    }
  }
}

// get an event when question(1) is updated
var msg = {
  stream: "questions",
  payload: {
    action: "subscribe"
    data: {
      action: "update",
      pk: "1"
    }
  }
}

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