Yasuhiro Matsuda created KAFKA-3271:
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Summary: Notification upon unclean leader election
Key: KAFKA-3271
URL: https://issues.apache.org/jira/browse/KAFKA-3271
Project: Kafka
Issue Type: New Feature
Components: clients, core
Reporter: Yasuhiro Matsuda
Priority: Minor
It is a legitimate restriction that unclean leader election results in some
message loss. That said, it is always good to try to minimize the message loss.
A notification of unclean leader election can reduce message loss in the
following scenario.
1. The latest offset is L.
2. A consumer is at C, where C < L
3. A slow broker (not in ISR) is at S, where S < C
4. All brokers in ISR die.
5. The slow broker becomes a leader by unclean leader election.
6. Now the offset of S.
7. The new messages get offsets S, S+1, S+2, and so on.
Currently the consumer won't receive new messages of offsets between S and C.
However, if the consumer is notified when unclean leader election happened and
resets its offset to S, it can receive new messages between S and C.
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