Unsubscribe all clients from replica for shard channel if the master ownership changes by hpatro · Pull Request #12577 · redis/redis

hpatro · 2023-09-14T02:07:38Z

Release notes
Fix a bug where a replica would continue to serve slots it doesn't have data for after switching masters which owns different slots.

…ownership changes

zuiderkwast

It seems reasonable to unsubscribe clients from shard channels when the shard changes.

Do we ever do this for regular subscribe channels and patterns?

I'm not sure all clients can handle a 'sunsubscribe' message without first having sent a SUNSUBSCRIBE command. Maybe not even redis-cli can handle this. We should check.

We need to clarify in the docs that the client can receive 'sunsubscribe' messages even when they haven't sent SUNSUBSCRIBE.

hpatro · 2023-09-15T09:50:39Z

Do we ever do this for regular subscribe channels and patterns?

No, not that I'm aware of.

I'm not sure all clients can handle a 'sunsubscribe' message without first having sent a SUNSUBSCRIBE command. Maybe not even redis-cli can handle this. We should check.

We need to clarify in the docs that the client can receive 'sunsubscribe' messages even when they haven't sent SUNSUBSCRIBE.

This is already the behavior when individual slots get migrated from one node to another. Node migration scenario wasn't covered. Yeah, we could document this for client(s) to take action (possibly disconnect and reconnect the client) and improve redis-cli first. I will follow up on both of these.

Co-authored-by: Madelyn Olson <34459052+madolson@users.noreply.github.com>

madolson · 2023-10-12T18:09:18Z

Not back porting immediately as there is no immediate need. If it comes up, we can backport and release.

Unsubscribe all clients from replica for shard channel if the master …

2501388

…ownership changes

hpatro requested review from enjoy-binbin, madolson and zuiderkwast September 14, 2023 16:31

zuiderkwast reviewed Sep 15, 2023

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