raft: reject linearizable_barrier if not is_leader() #10921
Merged
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A test noticed that a Kafka ListOffsets request issued concurrently with raft election could return a commit_index lower than the last message committed on the previous leader.
To the client this looks like time travel on their topic's HWM.
We could special case this for ListOffsets, but linearizable_barrier is used lots of places, and probably none of them actually want to run in this brief millisecond between leader election and is_leader() becoming true.
Fixes #10885
Backports Required
Release Notes
Bug Fixes