Django channels blocks on database access - django-channels

Question

I am upgrading current project from channel v1 to v3 and I am bit stuck here
class MultiplexConsumer(WebsocketConsumer):
def connect(self):
print(11111111, self.scope)
logger.debug("Received new connection request from {}", self.channel_name)
WebSocketsConnection.objects.create(channel_id=self.channel_name, last_pong=datetime.datetime.now())
print(444444444)
self.accept()
print(555555555)
...
class WebSocketsConnection(models.Model):
"""
This model exists because Django channels does not provide a default way to handle user presence.
"""
id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
channel_id = models.CharField(max_length=50)
user = models.ForeignKey(User, null=True, blank=True, on_delete=models.deletion.SET_NULL)
last_pong = models.DateTimeField(auto_now_add=True)
type = models.CharField(max_length=30, null=True, blank=True)
data = JSONField(default={})
def ping(self):
channel_layer = get_channel_layer()
async_to_sync(channel_layer.send)(self.channel_id, create_action('API', APIConstants.PING), immediately=True)
def pong(self):
self.last_pong = timezone.now()
self.save()
def get_groups(self):
groups = []
for sub in WebSocketsConnectionSubscription.objects.filter(ws_connection=self):
groups.append(sub.get_group_id())
return groups
def _add_subscription(self, data, sub_type):
try:
sub = WebSocketsConnectionSubscription.objects.get(ws_connection=self, type=sub_type)
sub.data = data
sub.save()
except WebSocketsConnectionSubscription.DoesNotExist:
WebSocketsConnectionSubscription.objects.create(ws_connection=self, data=data, type=sub_type)
It never prints 444444444, if I remove the WebSocketsConnection model creation statement, it flows fine. Any ideas?
I checked there are not model signals attached to WebSocketsConnection

Answer 1

I managed to find out the problem, the value of self.channel_name is too long for the field channel_id = models.CharField(max_length=50)
Once I changed it to 100 chars then it worked fine, but why it was not throwing any errors was still unknown.
UPDATE: It's a known problem that consumers not propagating the error up How to see exceptions raised from a channels consumer