Django Channels 2 Group_send to channel layer causes runtime error: "got Future attached to a different loop"

[Luke Hebert]

Trying to call the "alert_receive" consumer method

import json

from channels.consumer import SyncConsumer

from channels.exceptions import StopConsumer

from asgiref.sync import async_to_sync

from channels.layers import get_channel_layer

class ClientAlertPtrConsumer(SyncConsumer):
    def websocket_connect(self, event):
        async_to_sync(self.channel_layer.group_add)("AlertReceivers", self.channel_name)
        self.send({
                "type": "websocket.accept",
            })
   
    def websocket_receive(self, event):
        content = json.dumps("received")
        async_to_sync(self.channel_layer.group_send)("AlertReceivers", {"type":"alert.receive"})
        
    def websocket_disconnect(self, event):
        async_to_sync(self.channel_layer.group_discard)("AlertReceivers", self.channel_name)
        raise StopConsumer
       
    def alert_receive(self, event):                 # Get a message on the alert.receive type
        content = json.dumps("Group send working")
        self.send({
            "type":"websocket.send",                # then send a message out on websocket protocol to whatever the 'self' channel is.
            "text":content,
            })

from outside this consumer class using the approach in documentation like this

from asgiref.sync import async_to_sync
from channels.layers import get_channel_layer
channel_layer = get_channel_layer()

async_to_sync(channel_layer.group_send)("AlertReceivers", {'type':"alert.receive"})

and getting the following traceback having to do with the concurrent.futures module:

Traceback (most recent call last):

  File "/usr/lib/python3.5/code.py", line 91, in runcode

    exec(code, self.locals)

  File "<console>", line 1, in <module>

  File "/usr/local/lib/python3.5/dist-packages/asgiref/sync.py", line 49, in __call__

    return call_result.result()

  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 398, in result

    return self.__get_result()

  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 357, in __get_result

    raise self._exception

  File "/usr/local/lib/python3.5/dist-packages/asgiref/sync.py", line 63, in main_wrap

    result = await self.awaitable(*args, **kwargs)

  File "/usr/local/lib/python3.5/dist-packages/channels_redis/core.py", line 313, in group_send

    pool = await self.connection(self.consistent_hash(group))

  File "/usr/local/lib/python3.5/dist-packages/channels_redis/core.py", line 377, in connection

    self.pools[index] = await aioredis.create_redis_pool(**self.hosts[index])

  File "/usr/local/lib/python3.5/dist-packages/aioredis/commands/__init__.py", line 197, in create_redis_pool

    loop=loop)

  File "/usr/local/lib/python3.5/dist-packages/aioredis/pool.py", line 59, in create_pool

    await pool.wait_closed()

  File "/usr/local/lib/python3.5/dist-packages/aioredis/pool.py", line 177, in wait_closed

    await asyncio.shield(self._close_waiter, loop=self._loop)

  File "/usr/lib/python3.5/asyncio/futures.py", line 361, in __iter__

    yield self  # This tells Task to wait for completion.

RuntimeError: Task <Task pending coro=<AsyncToSync.main_wrap() running at /usr/local/lib/python3.5/dist-packages/asgiref/sync.py:63> cb=[_run_until_complete_cb() at /usr/lib/python3.5/asyncio/base_events.py:164]> got Future <Future pending> attached to a different loop

Note that the 

async_to_sync(channel_layer.group_send)("AlertReceivers", {'type':"alert.receive"})

within the websocket_receive method of the consumer class works well, sending the event out onto redis-based channel layers and then sending json encoded "Group send working" WS message to client. 

[Luke Hebert]

Trying to call a consumer method inside a SyncConsumer class

def alert_receive(self, event):                 # Get a message of the alert.receive type off of channel_layers

        content = json.dumps("Group send working")

        self.send({

            "type":"websocket.send",                # then send a message out on websocket protocol to whatever the 'self' channel is. 

            "text":content,

            })

from a python script outside of this consumer class using the approach from the docs:

from asgiref.sync import async_to_sync
from channels.layers import get_channel_layer
channel_layer = get_channel_layer()

async_to_sync(channel_layer.group_send)("AlertReceivers", {"type": "alert.receive"})

The last line there raises this traceback:

Note that if I do a 

async_to_sync(self.channel_layer.group_send)("AlertReceivers", {"type": "alert.receive"})

from within the consumer class, it works well and getting that alert.receive type event onto the channel_layer and sending the JSON encoded "Group send working" message out to all member channels of the group, just like it should do from outside the consumer. 

[Andrew Godwin]

Can you update your versions of `asgiref` and `channels_redis` please? I fixed those bugs a couple of days ago.

Andrew

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[raed]

how did you test it ? did you use a specific cmd to excute ?