I have a partial solution to this, if anybody is interested. For some
reason, creating a new version of the core.py file in which
RedisChannelLayer is defined, and editing it directly, gave the desired
results. It was something about overriding only part of it, but I have no
idea what!
On Friday, 23 March 2018 09:56:13 UTC, Alex wrote:
>
> I've been trying to add persistence to channel layers, such that each new
> consumer joining a group is sent the most recent message from that group,
> on connect. Below are my attempts. For some reason, the message in the
> highlighted line always seems to be of type 'None'. Am I going about this
> completely incorrectly? I'd be really grateful for any help.
>
>
> from channels_redis.core import RedisChannelLayer
> from channels.exceptions import ChannelFull
> import time
>
>
> class RedisChannelLayerGroupPersistence(RedisChannelLayer):
>
>
>
>
> async def group_send(self, group, message):
> """
> Sends a message to the entire group.
> """
> assert self.valid_group_name(group), "Group name not valid"
> # Retrieve list of all channel names
> key = self._group_key(group)
> pers_key = str(key) + "_PERS"
> async with self.connection(self.consistent_hash(group)) as
> connection:
> # Discard old channels based on group_expiry
> await connection.zremrangebyscore(key, min=0, max=int(time.
> time()) - self.group_expiry)
> # Return current lot
> channel_names = [
> x.decode("utf8") for x in
> await connection.zrange(key, 0, -1)
> ]
> # TODO: More efficient implementation (lua script per shard?)
> try:
> await connection.persist(pers_key)
> await connection.set(pers_key, str(message))
> print("TYPE =
> ================================================ {}".format(type(str(
> message))))
>
>
> for channel in channel_names:
> try:
> await self.send(channel, message)
> except ChannelFull:
> pass
>
>
> async def group_add(self, group, channel):
>
>
> """
> Adds the channel name to a group.
> """
> # Check the inputs
> assert self.valid_group_name(group), "Group name not valid"
> assert self.valid_channel_name(channel), "Channel name not valid"
> # Get a connection to the right shard
> group_key = self._group_key(group)
> pers_key = str(group_key) + "_PERS"
> async with self.connection(self.consistent_hash(group)) as
> connection:
> message = await connection.get(pers_key) #ISSUE HERE
> ------------------ MESSAGE IS NONE
> # Add to group sorted set with creation time as timestamp
> await connection.zadd(
> group_key,
> time.time(),
> channel,
> )
> # Set expiration to be group_expiry, since everything in
> # it at this point is guaranteed to expire before that
> try:
> await self.send(channel, str(message))
> except ChannelFull:
> pass
>
>
>
>
> await connection.expire(group_key, self.group_expiry)
>
>
>
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