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Motivation

, we optimize the beginQuorumEpochRequest timeout, 

The controller quorum fetch loop relies on a timing invariant for correctness and liveness: the  controller.quorum.fetch.timeout.ms must be significantly larger than Raft maximum fetch wait time(currently current hardcode to 500 ms) must be significantly smaller than half of the controller.quorum.fetch.timeout.ms ) after KAFKA-16926 Optimize BeginQuorumEpoch heartbeat.

In practice, the algorithm makes progress because:

raft_max_fetch_wait_time (500 ms) * 2  <=  controller.quorum.fetch.timeout.ms  * 2ms 

If operators set an unusually small controller.quorum.fetch.timeout.ms raft_max_fetch_wait_time * 2, this invariant can be violated, risking premature timeouts, spurious retries, and degraded stability. To preserve the invariant across configurations and upgrades, we propose to enforce a lower bound of 1000 ms for controller.quorum.fetch.timeout.ms.

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