Support subscriptions against cluster slave nodes #3480
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Hello @LINKIWI, this is a nice addition, I am working on something that touches the pubsub at the moment and would like to hold merging your PR once I am done. Do you have a need for this / is is urgent to merge? |
Thanks for the review. No worries, it is not urgent; happy to hold for now and rebase on top of the in-progress refactor once that is in. Thanks! |
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Currently,
SUBSCRIBE(and its sibling variant commands) establish connections only to masters, regardless of theReadOnlyoption specified in client options.This PR allows go-redis to respect the
ReadOnlyoption for subscriptions in the pubsub client, by preferring slave nodes for new connections. Note that in both global and sharded pubsub modes, messages are replicated to slaves by Redis.Note that
newConnin the pubsub client is only used for creating connections for long-lived subscriptions, so it does not need to consider any per-command R/W-family properties as in the case for commands outside of the pubsub client.I added a new unit test case for both global and sharded subscriptions with
ReadOnlyset to true, with an additional assertion on the value ofpubsub{shard}_channelsas returned byINFOto additionally verify that the subscription is served only by slave nodes.