Jason Gustafson created KAFKA-12619:
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Summary: Ensure LeaderChange message is committed before
initializing high watermark
Key: KAFKA-12619
URL: https://issues.apache.org/jira/browse/KAFKA-12619
Project: Kafka
Issue Type: Bug
Reporter: Jason Gustafson
Assignee: Jason Gustafson
KIP-595 describes an extra condition on commitment here:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-595%3A+A+Raft+Protocol+for+the+Metadata+Quorum#KIP595:ARaftProtocolfortheMetadataQuorum-Fetch.
In order to ensure that the leader's committed entries cannot get lost, it
must commit one record from its own epoch. This guarantees that its latest
entry is larger (in terms of epoch/offset) than any previously written record
which ensures that any future leader must also include it. This is the purpose
of the LeaderChange record which is written to the log as soon as the leader
gets elected.
We have this check implemented here:
https://github.com/apache/kafka/blob/trunk/raft/src/main/java/org/apache/kafka/raft/LeaderState.java#L122.
However, the check needs to be a strict inequality since the epoch start
offset does not reflect the LeaderChange record itself. In other words, the
check is off by one.
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