Django Channels 2.0.0 groups

[Ahmed Magdy]

I'm relatively new to channels and was using Channels v1.x.x groups easily, but after v2.0.0 update and reading the documentation

# This example uses WebSocket consumer, which is synchronous, and so
# needs the async channel layer functions to be converted.
from asgiref.sync import AsyncToSync

class ChatConsumer(WebsocketConsumer):

    def connect(self):
        AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)

    def disconnect(self):
        AsyncToSync(self.channel_layer.group_discard)("chat", self.channel_name)

Enter code here...

channel_layer, channel_name are always NoneType and exception occurs.

Is that because I didn't configure channel layers? But in the old version I also used the in memory type and Groups were working well.

[Andrew Godwin]

Hi Ahmed,

In the new release channel layers are optional - if you don't configure them they will indeed come through as None. The settings format changed slightly too - you can read more here: http://channels.readthedocs.io/en/latest/topics/channel_layers.html

Andrew

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[Ahmed Magdy]

That's what I did after reading the documentation here's how my channels files look like

# settings.py

# ...

ASGI_APPLICATION = 'djangoChannels.routing.application'

# ...

# routing.py

from django.conf.urls import url

from channels.routing import ProtocolTypeRouter, URLRouter

from channels.auth import AuthMiddlewareStack

from .consumers import ChatConsumer

application = ProtocolTypeRouter({

   # Empty for now (http->django views is added by default)

   'websocket': AuthMiddlewareStack(

       URLRouter([

           url('^sessions/$', ChatConsumer)

       ])

   )

})

# consumers.py

from asgiref.sync import AsyncToSync

from channels.generic.websocket import WebsocketConsumer

class ChatConsumer(WebsocketConsumer):

    def connect(self):

       AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)

    def disconnect(self):

       AsyncToSync(self.channel_layer.group_discard)("chat", self.channel_name)

After connecting with JS websocket to

ws://127.0.0.1:8000/sessions/

Raises an exception

Performing system checks...

System check identified no issues (0 silenced).
February 03, 2018 - 03:14:29
Django version 2.0.2, using settings 'djangoChannels.settings'
Starting ASGI/Channels development server at http://127.0.0.1:8000/
Quit the server with CTRL-BREAK.
2018-02-03 03:14:29,799 - INFO - server - HTTP/2 support not enabled (install the http2 and tls Twisted extras)
2018-02-03 03:14:29,800 - INFO - server - Listening on endpoint tcp:port=8000:interface=127.0.0.1
[2018/02/03 03:14:32] WebSocket HANDSHAKING /sessions/ [127.0.0.1:8631]
ERROR:root:Exception inside application: 'NoneType' object has no attribute 'group_add'
  File "c:\python35\Lib\asyncio\tasks.py", line 241, in _step
    result = coro.throw(exc)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 53, in __call__
    await await_many_dispatch([receive], self.dispatch)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\utils.py", line 48, in await_many_dispatch
    await dispatch(result)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 84, in inner
    return await async_func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 67, in __call__
    return await asyncio.wait_for(future, timeout=None)
  File "c:\python35\Lib\asyncio\tasks.py", line 367, in wait_for
    return (yield from fut)
  File "c:\python35\Lib\asyncio\futures.py", line 358, in __iter__
    yield self  # This tells Task to wait for completion.
  File "c:\python35\Lib\asyncio\tasks.py", line 290, in _wakeup
    future.result()
  File "c:\python35\Lib\asyncio\futures.py", line 274, in result
    raise self._exception
  File "c:\python35\Lib\concurrent\futures\thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 76, in thread_handler
    raise e
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 74, in thread_handler
    self.func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 93, in dispatch
    handler(message)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\generic\websocket.py", line 19, in websocket_connect
    self.connect()
  File "D:\Programming\DjangoWebsite\HUWebsite\husite\djangoChannels\djangoChannels\consumers.py", line 8, in connect
    AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)
  'NoneType' object has no attribute 'group_add'
[2018/02/03 03:14:32] WebSocket DISCONNECT /sessions/ [127.0.0.1:8631]

On Friday, February 2, 2018 at 7:37:36 PM UTC+2, Andrew Godwin wrote:

Hi Ahmed,

In the new release channel layers are optional - if you don't configure them they will indeed come through as None. The settings format changed slightly too - you can read more here: http://channels.readthedocs.io/en/latest/topics/channel_layers.html

Andrew

On Fri, Feb 2, 2018 at 3:31 AM, Ahmed Magdy <ahmed...@gmail.com> wrote:

I'm relatively new to channels and was using Channels v1.x.x groups easily, but after v2.0.0 update and reading the documentation

# This example uses WebSocket consumer, which is synchronous, and so
# needs the async channel layer functions to be converted.
from asgiref.sync import AsyncToSync

class ChatConsumer(WebsocketConsumer):

    def connect(self):
        AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)

    def disconnect(self):
        AsyncToSync(self.channel_layer.group_discard)("chat", self.channel_name)

Enter code here...

channel_layer, channel_name are always NoneType and exception occurs.

Is that because I didn't configure channel layers? But in the old version I also used the in memory type and Groups were working well.

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[Andrew Godwin]

Do you have a CHANNEL_LAYERS setting in your settings file? If so, what is it set to?

Andrew

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[Ahmed Magdy]

I tried not having CHANNEL_LAYERS or setting it to {}
same exception

[Andrew Godwin]

It needs to contain a value to work - what value were you trying that was not empty?

Andrew

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[Ahmed Magdy]

I thought it uses in memory channel layer by default if it's empty? I didn't try setting a value, because only redis was available in v2.0.0 and I don't like using stuff I don't understand.

[Andrew Godwin]

No, there is no in-memory channel layer any more, only Redis is available at the moment. You must put something into the settings in order to make it function.

Andrew

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[Ahmed Magdy]

Aha thanks for making it clear, I will read more about redis then. Shouldn't the docs mention that though?

[Andrew Godwin]

The docs do mention this in a big callout at the top of the Channel Layers page :) http://channels.readthedocs.io/en/latest/topics/channel_layers.html

Andrew

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[Ahmed Magdy]

I even made sure to read the docs multiple times before posting. :/

I've been reading about Redis, and since I got windows OS, I installed the port for Windows based redis, tested the server and client they are working ok.

# settings.py

# ...

ASGI_APPLICATION = 'djangoChannels.routing.application'

CHANNEL_LAYERS = {

   "default": {

       "BACKEND": "channels_redis.core.RedisChannelLayer",

       "CONFIG": {

           "hosts": [("localhost", 6379)],

       },

   },

}

# consumers.py

from asgiref.sync import AsyncToSync

from channels.generic.websocket import WebsocketConsumer

class ChatConsumer(WebsocketConsumer):

   def connect(self):

       AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)

    def disconnect(self):

       AsyncToSync(self.channel_layer.group_discard)("chat", self.channel_name)

raises an exception

[2018/02/03 08:30:19] WebSocket HANDSHAKING /sessions/ [127.0.0.1:12778]
ERROR:root:Exception inside application: There is no current event loop in thread 'Thread-3'.

  File "c:\python35\Lib\asyncio\tasks.py", line 241, in _step
    result = coro.throw(exc)

  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 51, in __call__
    await await_many_dispatch([receive, self.channel_receive], self.dispatch)

  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\utils.py", line 48, in await_many_dispatch
    await dispatch(result)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 84, in inner
    return await async_func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 67, in __call__
    return await asyncio.wait_for(future, timeout=None)
  File "c:\python35\Lib\asyncio\tasks.py", line 367, in wait_for
    return (yield from fut)
  File "c:\python35\Lib\asyncio\futures.py", line 358, in __iter__
    yield self  # This tells Task to wait for completion.
  File "c:\python35\Lib\asyncio\tasks.py", line 290, in _wakeup
    future.result()
  File "c:\python35\Lib\asyncio\futures.py", line 274, in result
    raise self._exception
  File "c:\python35\Lib\concurrent\futures\thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 76, in thread_handler
    raise e
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 74, in thread_handler
    self.func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 93, in dispatch
    handler(message)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\generic\websocket.py", line 19, in websocket_connect
    self.connect()

  File "D:\Programming\DjangoWebsite\HUWebsite\husite\djangoChannels\djangoChannels\consumers.py", line 7, in connect
    AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 17, in __init__
    self.main_event_loop = asyncio.get_event_loop()
  File "c:\python35\Lib\asyncio\events.py", line 626, in get_event_loop
    return get_event_loop_policy().get_event_loop()
  File "c:\python35\Lib\asyncio\events.py", line 572, in get_event_loop
    % threading.current_thread().name)
  There is no current event loop in thread 'Thread-3'.

Thanks for what you did so far!

[Andrew Godwin]

Yup, that looks like a genuine bug, I have opened a GitHub issue to track it: https://github.com/django/channels/issues/848

Andrew

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[Ahmed Magdy]

Since you closed the issue, I'm posting here.
Ok, so I've updated asgiref package to 2.1.1 and now getting different exception.

[2018/02/03 09:29:23] WebSocket HANDSHAKING /sessions/ [127.0.0.1:13235]
ERROR:root:Exception inside application: '_WindowsSelectorEventLoop' object has no attribute 'create_future'

  File "c:\python35\Lib\asyncio\tasks.py", line 241, in _step
    result = coro.throw(exc)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 51, in __call__
    await await_many_dispatch([receive, self.channel_receive], self.dispatch)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\utils.py", line 48, in await_many_dispatch
    await dispatch(result)

  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 99, in inner
    return await async_func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 79, in __call__

    return await asyncio.wait_for(future, timeout=None)
  File "c:\python35\Lib\asyncio\tasks.py", line 367, in wait_for
    return (yield from fut)
  File "c:\python35\Lib\asyncio\futures.py", line 358, in __iter__
    yield self  # This tells Task to wait for completion.
  File "c:\python35\Lib\asyncio\tasks.py", line 290, in _wakeup
    future.result()
  File "c:\python35\Lib\asyncio\futures.py", line 274, in result
    raise self._exception
  File "c:\python35\Lib\concurrent\futures\thread.py", line 55, in run
    result = self.fn(*self.args, **self.kwargs)

  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 91, in thread_handler
    raise e
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 89, in thread_handler

    self.func(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\consumer.py", line 93, in dispatch
    handler(message)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels\generic\websocket.py", line 19, in websocket_connect
    self.connect()
  File "D:\Programming\DjangoWebsite\HUWebsite\husite\djangoChannels\djangoChannels\consumers.py", line 7, in connect
    AsyncToSync(self.channel_layer.group_add)("chat", self.channel_name)

  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 45, in __call__
    call_result.result()
  File "c:\python35\Lib\concurrent\futures\_base.py", line 405, in result
    return self.__get_result()
  File "c:\python35\Lib\concurrent\futures\_base.py", line 357, in __get_result
    raise self._exception
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\asgiref\sync.py", line 53, in main_wrap
    result = await self.awaitable(*args, **kwargs)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 280, in group_add
    pool = await self.connection(self.consistent_hash(group))
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 377, in connection
    self.pools[index] = await aioredis.create_redis_pool(**self.hosts[index])
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\commands\__init__.py", line 197, in create_redis_pool
    loop=loop)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\pool.py", line 56, in create_pool
    await pool._fill_free(override_min=False)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\pool.py", line 388, in _fill_free
    conn = await self._create_new_connection(address)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\connection.py", line 124, in create_connection
    loop=loop)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\connection.py", line 163, in __init__
    self._close_waiter = loop.create_future()
  '_WindowsSelectorEventLoop' object has no attribute 'create_future'
[2018/02/03 09:29:24] WebSocket DISCONNECT /sessions/ [127.0.0.1:13235]
[2018/02/03 09:30:24] HTTP GET /sessions/ 503 [60.64, 127.0.0.1:13235]
ERROR:asyncio:Task exception was never retrieved
future: <Task finished coro=<receive() done, defined at D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py:137> exception=AttributeError("'_WindowsSelectorEventLoop'
object has no attribute 'create_future'",)>
Traceback (most recent call last):
  File "c:\python35\Lib\asyncio\tasks.py", line 239, in _step
    result = coro.send(None)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 158, in receive
    return await self.receive_buffer_lpop(channel)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 220, in receive_buffer_lpop
    task.result()

  File "c:\python35\Lib\asyncio\futures.py", line 274, in result
    raise self._exception

  File "c:\python35\Lib\asyncio\tasks.py", line 239, in _step
    result = coro.send(None)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 171, in receive_loop
    real_channel, message = await self.receive_single(channel)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 187, in receive_single
    pool = await self.connection(index)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\channels_redis\core.py", line 377, in connection
    self.pools[index] = await aioredis.create_redis_pool(**self.hosts[index])
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\commands\__init__.py", line 197, in create_redis_pool
    loop=loop)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\pool.py", line 56, in create_pool
    await pool._fill_free(override_min=False)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\pool.py", line 388, in _fill_free
    conn = await self._create_new_connection(address)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\connection.py", line 124, in create_connection
    loop=loop)
  File "D:\Programming\DjangoWebsite\HUWebsite\lib\site-packages\aioredis\connection.py", line 163, in __init__
    self._close_waiter = loop.create_future()
AttributeError: '_WindowsSelectorEventLoop' object has no attribute 'create_future'

[Andrew Godwin]

That looks like a problem with the version of Python you are running - what version is it?

Andrew

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[Ahmed Magdy]

v3.5.1:37a07cee5969

[Andrew Godwin]

Ah, yes, it looks like aioredis requires at least 3.5.2. I will update the channels_redis readme to make this clear.

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[Ahmed Magdy]

Finally, I think reverting back to channels 1.x.x was much easier for you and me. ^^
Really appreciate what you did and the project, now I can implement the chatting functionality for my graduation project.