Jose Armando Garcia Sancio created KAFKA-13621:
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Summary: Resign leader on partition
Key: KAFKA-13621
URL: https://issues.apache.org/jira/browse/KAFKA-13621
Project: Kafka
Issue Type: Sub-task
Reporter: Jose Armando Garcia Sancio
Assignee: Jose Armando Garcia Sancio
h1. Motivation
If the current leader A at epoch X gets partition from the rest of the quorum,
quorum voter A will stay leader at epoch X. This happens because voter A will
never receive an request from the rest of the voters increasing the epoch.
These requests that typically increase the epoch of past leaders are
BeginQuorumEpoch and Vote.
In addition if voter A (leader at epoch X) doesn't get partition from the rest
of the brokers (observer in the KRaft protocol) the brokers will never learn
about the new quorum leader. This happens because 1. observers learn about the
leader from the Fetch response and 2. observer send a Fetch request to a random
leader if the Fetch request times out.
Neither of these two scenarios will cause the broker to send a request to a
different voter because the leader at epoch X will never send a different
leader in the response and the broker will never send a Fetch request to a
different voter because the Fetch request will never timeout.
h1. Proposed Changes
In this scenario the A, the leader at epoch X, will stop receiving Fetch
request from the majority of the voters. Voter A should resign as leader if the
Fetch request from the majority of the voters is old enough. A reasonable value
for "old enough" is the Fetch timeout value.
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