django channels - delayed messaging does not work - django

Question

I am trying to imitate a time consuming django response, by delaying group message in Django channels, but it does not work.
The consumer is very simple:
class ExportConsumer(JsonWebsocketConsumer):
...
def delayed_message(self, event):
print("In delayed")
time.sleep(5)
self.send(text_data=json.dumps({
'message': 'delayed!'
}))
def immediate_message(self, event):
print("In Immediate")
self.send(text_data=json.dumps({
'message': 'immediate_message!'
}))
and in views I just send to a group two messages - for delayed and immediate processing:
class DecisionListView(PaginatedListView):
...
def get(self, *args, **kwargs):
async_to_sync(get_channel_layer().group_send)(
'5e001793-18be-4a4b-8caf-c4a8144a11d2',
{
'type': 'immediate_message',
'message': 'message'
}
)
async_to_sync(get_channel_layer().group_send)(
'5e001793-18be-4a4b-8caf-c4a8144a11d2',
{
'type': 'delayed_message',
'message': 'message'
}
)
return super().get(*args, **kwargs)
The 'immediate message' is delivered. And I get In delayed on terminal (which means that it reaches the delayed_message but the message is never delivered (unless I comment out time.sleep.
What am I doing wrong?
UPDATE::
AsyncJsonWebsocketConsumer does not work as well:
consumers.py:
class ExportConsumer(AsyncJsonWebsocketConsumer):
...
async def delayed_message(self, event):
await asyncio.sleep(5)
await self.send(text_data=json.dumps({
'message': 'whatever'
}))
views.py:
class DecisionListView(PaginatedListView):
...
def get(self, *args, **kwargs):
_group_send = get_channel_layer().group_send
_sync_group_send = async_to_sync(_group_send)
_sync_group_send('5e001793-18be-4a4b-8caf-c4a8144a11d2',{"type":'delayed_message', 'message':'hello'})
return super().get(*args, **kwargs)
UPDATE2:
The only thing that works for me is asyncio.create_task:
class ExportConsumer(AsyncJsonWebsocketConsumer):
async def delayed_task(self):
await asyncio.sleep(5)
await self.channel_layer.group_send(
self.room_group_name,
{
'type': 'chat_message',
'message': 'LATER'
}
)
async def delayed_message(self, event):
asyncio.create_task(self.delayed_task())
await self.send_json('NOW')
async def chat_message(self, event):
message = event['message']
await self.send_json(message)

Answer 1

you should be using an AsyncJsonWebsocketConsumer and async methods then you can use the sleep method from asyncio.
time.sleep will block your entire server.
-- unrelated
you should be sending delayed.message not delayed_message (channels replaces . with _ when calling functions)