For Pub sub cluster using the io.lettuce.core.pubsub.PubSubCommandArgs, due which does not make use of hash and does not distribute the channels across shards

[ramnaresh2051]

Bug Report

For Pub sub cluster using the io.lettuce.core.pubsub.PubSubCommandArgs,
And in this below overridden method, which always return null key
@OverRide
public ByteBuffer getFirstEncodedKey() {
return null;
}

due which does not make use of hash key and does not distribute the data(channel subscription) across the shards.

Current Behavior

ClusterDistributionChannelWriter -->
ByteBuffer encodedKey = args.getFirstEncodedKey(); // this gets called to identify the encoded key, however due to PubSubCommandArgs above behaviour its always return null and complete data(channel subscription) goes to one shard only.

Expected behavior/code

Pubsub should make use of CommandArgs instead of PubSubCommandArgs Or should provide a option to override this.

Environment

• Lettuce version(s): [6.2.6.RELEASE]

Possible solutions

RedisPubSubReactiveCommandsImpl -- a option can be provided to pass CommandArgs while creating cluster client as a client options.

[mp911de]

Care to elaborate on what you're trying to achieve? Cluster Pub/Sub messages get replicated to each cluster node so there's no point in applying key slot hashing.

On the other side, shared Pub/Sub, would benefit from such routing, see #1984

[ramnaresh2051]

So do we have any plan to implement #1984 ?
Intentionally for pubsub we have dropped slot hashing, did we face any performance issue for that ?

[mp911de]

I don't know about you, but I have a plan to eventually implement the feature. Getting support from users and the community would help to speed up the process.

Intentionally for pubsub we have dropped slot hashing, did we face any performance issue for that ?

Yes, that is by intent. Routing Pub/Sub commands to the default connection avoids creating additional connections to cluster nodes.