djangochannelsrestframework 1.3.0
RESTful API for WebSockets using django channels.
License: MIT
Requires Python: >=3.8

==============================
Django Channels Rest Framework
==============================

Django Channels Rest Framework provides a DRF like interface for building channels-v4_ websocket consumers.


This project can be used alongside HyperMediaChannels_ and ChannelsMultiplexer_ to create a Hyper Media Style api over websockets. However Django Channels Rest Framework is also a free standing framework with the goal of providing an api that is familiar to DRF users.

theY4Kman_ has developed a useful Javascript client library dcrf-client_ to use with DCRF.

Thanks to
---------


DCRF is based of a fork of `Channels Api <https://github.com/linuxlewis/channels-api>`_ and of course inspired by `Django Rest Framework <http://www.django-rest-framework.org/>`_.

Documentation
-------------
ReadTheDocs_


Install
-------

.. code-block:: bash
  
  pip install djangochannelsrestframework


.. warning ::

            In your application definition when you declare your consumers it is very important to use the ``.as_asgi()`` class method (e.g. ``MyConsumer.as_asgi()``). You **should not** have any instances of ``MyConsumer()`` in your code base.



A Generic Api Consumer
----------------------
In DCRF you can create a ``GenericAsyncAPIConsumer`` that works much like a GenericAPIView_ in DRF: For a more indepth look into Rest-Like Websocket consumers read this blog post_.


.. code-block:: python

    from . import models
    from . import serializers
    from djangochannelsrestframework import permissions
    from djangochannelsrestframework.generics import GenericAsyncAPIConsumer
    from djangochannelsrestframework.mixins import (
        ListModelMixin,
        PatchModelMixin,
        UpdateModelMixin,
        CreateModelMixin,
        DeleteModelMixin,
    )

    class LiveConsumer(ListModelMixin, GenericAsyncAPIConsumer):
        queryset = models.Test.objects.all()
        serializer_class = serializers.TestSerializer
        permission_classes = (permissions.IsAuthenticated,)


Because this class uses the ``ListModelMixin``, one has access to the ``list`` action.

One may use the same exact querysets and ``serializer_class`` utilized in their DRF Views, but must omit the DRF permissions. Permissions are to be imported from ``djangochannelsrestframework``, which provides the standard ``AllowAny`` and ``IsAuthenticated`` permissions.

To call an action from the client send a websocket message: ``{action: "list", "request_id": 42}``


There are a selection of mixins that expose the common CRUD actions:

* ``ListModelMixin`` - ``list``
* ``PatchModelMixin`` - ``patch``
* ``CreateModelMixin`` - ``create``
* ``RetrieveModelMixin`` - ``retrieve``
* ``UpdateModelMixin`` - ``update``
* ``DeleteModelMixin`` - ``delete``


Observing a Model instance
--------------------------

Consumer that let you subscribe to changes on an instance:

.. code-block:: python

   class TestConsumer(ObserverModelInstanceMixin, GenericAsyncAPIConsumer):
       queryset = get_user_model().objects.all()
       serializer_class = UserSerializer

this exposes the ``retrieve``, ``subscribe_instance`` and ``unsubscribe_instance`` actions.

To subscribe send:

.. code-block:: python

   {
       "action": "subscribe_instance",
       "pk": 42,  # the id of the instance you are subscribing to
       "request_id": 4  # this id will be used for all result updates.
   }


Actions will be sent down out from the server:

.. code-block:: python

  {
    "action": "update",
    "errors": [],
    "response_status": 200,
    "request_id": 4,
    "data": {'email': '42@example.com', 'id': 42, 'username': 'thenewname'},
  }

Adding Custom actions
---------------------


.. code-block:: python

   class UserConsumer(GenericAsyncAPIConsumer):
       queryset = get_user_model().objects.all()
       serializer_class = UserSerializer

       @action()
       async def send_email(self, pk=None, to=None, **kwargs):
           user = await database_sync_to_async(self.get_object)(pk=pk)
           # ... do some stuff
           # remember to wrap all db actions in `database_sync_to_async`
           return {}, 200  # return the context and the response code.

       @action()  # if the method is not async it is already wrapped in `database_sync_to_async`
       def publish(self, pk=None, **kwargs):
           user = self.get_object(pk=pk)
           # ...
           return {'pk': pk}, 200

Consumers that are not bound to Models
--------------------------------------

You can also create consumers that are not at all related to any models.

.. code-block:: python

  from djangochannelsrestframework.decorators import action
  from djangochannelsrestframework.consumers import AsyncAPIConsumer


  class MyConsumer(AsyncAPIConsumer):

      @action()
      async def an_async_action(self, some=None, **kwargs):
          # do something async
          return {'response with': 'some message'}, 200
      
      @action()
      def a_sync_action(self, pk=None, **kwargs):
          # do something sync
          return {'response with': 'some message'}, 200

Using your normal views over a websocket connection
---------------------------------------------------

.. code-block:: python
  
  from djangochannelsrestframework.consumers import view_as_consumer

  application = ProtocolTypeRouter({
      "websocket": AuthMiddlewareStack(
          URLRouter([
              url(r"^front(end)/$", view_as_consumer(YourDjangoView)),
          ])
      ),
   })



In this situation if your view needs to read the `GET` query string values you can provides these using the `query` option.
And if the view method reads parameters from the URL you can provides these with the `parameters`.

Sending the following over your WS connection will result in a GET request being evaluated on your View.

.. code-block:: javascript

    {
      action: "retrieve",
      query: {"user_id": 42}
      parameters: {"project_id": 92}
    }



Subscribing to a signal.
------------------------

One can subscribe to a custom ``Signal`` utilizing the ``observer`` decorator.

Here we have a custom signal that will be triggered when a user join a chat.

.. code-block:: python

    # signals.py
    from django.dispatch.dispatcher import Signal

    joined_chat_signal = Signal()

Now we will create the consumer with two actions, one for subscribing to our custom signal for specific chat, and another one 
for manually trigger the signal.

.. code-block:: python

    # consumers.py
    from djangochannelsrestframework.consumers import AsyncAPIConsumer
    from djangochannelsrestframework.decorators import action
    from djangochannelsrestframework.observer import observer
    from rest_framework import status
    from .signals import joined_chat_signal
    from .serializers import UserSerializer


    class TestConsumer(AsyncAPIConsumer):

        @action()
        def join_chat(self, chat_id, **kwargs):
            serializer = UserSerializer(instance=self.scope['user'])
            joined_chat_signal.send(sender='join_chat', data=serializer.data, **kwargs)
            return {}, status.HTTP_204_NO_CONTENT

        @observer(signal=joined_chat_signal)
        async def joined_chat_handler(self, data, observer=None, action=None, subscribing_request_ids=[], **kwargs):
            for request_id in subscribing_request_ids:
                await self.reply(action='joined_chat', data=data, status=status.HTTP_200_OK, request_id=request_id)

        @joined_chat_handler.serializer
        def join_chat_handler(self, sender, data, **kwargs): # the data comes from the signal.send and will be available in the observer
            return data

        @joined_chat_handler.groups_for_signal
        def joined_chat_handler(self, instance, **kwargs):
            yield f'chat__{instance}'

        @joined_chat_handler.groups_for_consumer
        def joined_chat_handler(self, chat, **kwargs):
            if chat:
                yield f'chat__{chat}'

        @action()
        async def subscribe_joined(self, chat_id, request_id, **kwargs):
            await self.joined_chat_handler.subscribe(chat_id, request_id=request_id)


Subscribing to all instances of a model
---------------------------------------

One can subscribe to all instances of a model by utilizing the ``model_observer``.

.. code-block:: python

    from djangochannelsrestframework.observer import model_observer

    @model_observer(models.Test)
    async def model_activity(self, message, observer=None, action=None, **kwargs):
        # send activity to your frontend
        await self.send_json(message)

This method will send messages to the client on all CRUD operations made through the Django ORM. The `action` arg here it will take values such as `create`, `delete` and `update` you should consider passing this to your frontend client.

Note: These notifications do not include bulk updates, such as ``models.Test.objects.filter(name="abc").update(name="newname")``


    **WARNING**
    When using this to decorate a method to avoid the method firing multiple
    times you should ensure that if there are multiple `@model_observer`
    wrapped methods for the same model type within a single file that each
    method has a different name.


Subscribing to a `model_observer`
=================================

You can do this in a few placed, a common example is in the ``websocket_connect`` method.

.. code-block:: python

    async def websocket_connect(self, message):

        # Super Save
        await super().websocket_connect(message)

        # Initialized operation
        await self.activities_change.subscribe()


This method utilizes the previously mentioned ``model_activity`` method to subscribe to all instances of the current Consumer's model.

One can also subscribe by creating a custom action

Another way is override ``AsyncAPIConsumer.accept(self, **kwargs)``

.. code-block:: python

    class ModelConsumerObserver(AsyncAPIConsumer):

        async def accept(self, **kwargs):
            await super().accept(** kwargs)
            await self.model_change.subscribe()

        @model_observer(models.Test)
        async def model_change(self, message, action=None, **kwargs):
            """
            This method is evaluated once for every user that subscribed,
            here you have access to info about the user by reading `self.scope`

            However it is best to avoid doing DB quires here since if you have lots of
            subscribers to a given instance you will end up with a LOT of database traffic.
            """
            await self.send_json(message)
        
        # If you want the data serialized instead of pk
        @model_change.serializer
        def model_serialize(self, instance, action, **kwargs):
            """
            This block is evaluated before the data is sent over the channel layer
            this means you are unable to access information
            such as the user that it will be sent to.

            If you need the user info when serializing then you can do the serialization
            in the above method.
            """
            return TestSerializer(instance).data

.. note::

    New Feature!
    Now you can rewrite this as:
    
.. code-block:: python

    class ModelConsumerObserver(AsyncAPIConsumer):

        async def accept(self, **kwargs):
            await super().accept(** kwargs)
            await self.model_change.subscribe()

        @model_observer(models.Test, serializer_class=TestSerializer)
        async def model_change(self, message, action=None, **kwargs):
            # in this case since we subscribe int he `accept` method
            # we do not expect to have any `subscribing_request_ids` to loop over.
            await self.reply(data=message, action=action)



Subscribing to a filtered list of models
========================================

In most situations you want to filter the set of models that you subscribe to.

To do this we need to split the model updates into `groups` and then in the consumer subscribe to the groups that we want/have permission to see.


.. code-block:: python

  class MyConsumer(AsyncAPIConsumer):
    # This class MUST subclass `AsyncAPIConsumer` to use `@model_observer`

    @model_observer(models.Classroom)
    async def classroom_change_handler(
        self,
        message,
        observer=None,
        action=None,
        subscribing_request_ids=[],
        **kwargs
    ):
        # due to not being able to make DB QUERIES when selecting a group
        # maybe do an extra check here to be sure the user has permission
        # send activity to your frontend
        for request_id in subscribing_request_ids:
            # we can send a separate message for each subscribing request
            # this lets ws clients rout these messages.
            await self.send_json(dict(body=message, action=action, request_id=request_id))
        # note if we do not pass `request_id` to the `subscribe` method
        # then `subscribing_request_ids` will be and empty list.

    @classroom_change_handler.groups_for_signal
    def classroom_change_handler(self, instance: models.Classroom, **kwargs):
        # this block of code is called very often *DO NOT make DB QUERIES HERE*
        yield f'-school__{instance.school_id}'
        yield f'-pk__{instance.pk}'

    @classroom_change_handler.groups_for_consumer
    def classroom_change_handler(self, school=None, classroom=None, **kwargs):
        # This is called when you subscribe/unsubscribe
        if school is not None:
            yield f'-school__{school.pk}'
        if classroom is not None:
            yield f'-pk__{classroom.pk}'

    @action()
    async def subscribe_to_classrooms_in_school(self, school_pk, request_id, **kwargs):
        # check user has permission to do this
        await self.classroom_change_handler.subscribe(school=school, request_id=request_id)

    @action()
    async def subscribe_to_classroom(self, classroom_pk, request_id, **kwargs):
        # check user has permission to do this
        await self.classroom_change_handler.subscribe(classroom=classroom, request_id=request_id)


.. _ReadTheDocs: https://djangochannelsrestframework.readthedocs.io/en/latest/
.. _post: https://lostmoa.com/blog/DjangoChannelsRestFramework/
.. _GenericAPIView: https://www.django-rest-framework.org/api-guide/generic-views/
.. _channels-v4: https://channels.readthedocs.io/en/latest/
.. _dcrf-client: https://github.com/theY4Kman/dcrf-client
.. _theY4Kman: https://github.com/theY4Kman
.. _HyperMediaChannels: https://github.com/hishnash/hypermediachannels
.. _ChannelsMultiplexer: https://github.com/hishnash/channelsmultiplexer