Jiangjie Qin created KAFKA-3003:
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Summary: The fetch.wait.max.ms is not honored when new log segment
rolled for low volume topics.
Key: KAFKA-3003
URL: https://issues.apache.org/jira/browse/KAFKA-3003
Project: Kafka
Issue Type: Bug
Reporter: Jiangjie Qin
Assignee: Jiangjie Qin
The problem we saw can be explained by the example below:
1. Message offset 100 is appended to partition p0, log segment 00000000.log. at
time T. After that no message is appended.
2. This message is replicated, leader replica update its
highWatermark.messageOffset=100, highWatermark.segmentBaseOffset=0.
3. At time T + retention.ms, because no message has been appended to current
active log segment for retention.ms, the last modified time of the current log
segment reaches retention time.
4. Broker rolls out a new log segment 00000001.log, and deletes the old log
segment 00000000.log. The new log segment in this case is empty because there
is no message appended.
5. In Log, the nextOffsetMetadata.segmentBaseOffset will be updated to the new
log segment's base offset, but nextOffsetMetadata.messageOffset does not
change. so nextOffsetMetadata.messageOffset=1,
nextOffsetMetadata.segmentBaseOffset=1.
6. Now a FetchRequest comes and try to fetch from offset 1,
fetch.wait.max.ms=1000.
7. In ReplicaManager, because there is no data to return, the fetch request
will be put into purgatory. When delayedFetchPurgatory.tryCompleteElseWatch()
is called, the DelayedFetch.tryComplete() compares replica.highWatermark and
the fetchOffset returned by log.read(), it will see the
replica.highWatermark.segmentBaseOffset=0 and fetchOffset.segmentBaseOffset=1.
So it will assume the fetch occurs on a later segment and complete the delayed
fetch immediately.
In this case, the replica.highWatermark was not updated because the
LogOffsetMetadata.preceds() only checks the messageOffset but ignored
segmentBaseOffset. The fix is to let LogOffsetMetadata first check the
messageOffset then check the segmentBaseOffset. So replica.highWatermark will
get updated after the follower fetches from the leader.
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