Anna Povzner created KAFKA-7104:
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Summary: ReplicaFetcher thread may die because of inconsistent log
start offset in fetch response
Key: KAFKA-7104
URL: https://issues.apache.org/jira/browse/KAFKA-7104
Project: Kafka
Issue Type: Bug
Affects Versions: 1.1.0, 1.0.0
Reporter: Anna Povzner
Assignee: Anna Povzner
What we saw:
The follower fetches offset 116617, which it was able successfully append.
However, leader's log start offset in fetch request was 116753, which was
higher than fetched offset 116617. When replica fetcher thread tried to
increment log start offset to leader's log start offset, it failed with
OffsetOutOfRangeException:
[2018-06-23 00:45:37,409] ERROR [ReplicaFetcher replicaId=1002, leaderId=1001,
fetcherId=0] Error due to (kafka.server.ReplicaFetcherThread)
kafka.common.KafkaException: Error processing data for partition X-N offset
116617
Caused by: org.apache.kafka.common.errors.OffsetOutOfRangeException: Cannot
increment the log start offset to 116753 of partition X-N since it is larger
than the high watermark 116619
In leader's log, we see that log start offset was incremented almost at the
same time (within one 100 ms or so).
[2018-06-23 00:45:37,339] INFO Incrementing log start offset of partition X-N
to 116753 in dir /kafka/kafka-logs (kafka.log.Log)
In leader's logic: ReplicaManager#ReplicaManager first calls readFromLocalLog()
that reads from local log and returns LogReadResult that contains fetched data
and leader's log start offset and HW. However, it then calls
ReplicaManager#updateFollowerLogReadResults() that may move leader's log start
offset and update leader's log start offset and HW in fetch response. If
deleteRecords() happens in between, it is possible that log start offset may
move beyond fetched offset. As a result, fetch response will contain fetched
data but log start offset that is beyond fetched offset (and indicate the state
on leader that fetched data does not actually exist anymore on leader).
When a follower receives such fetch response, it will first append, then move
it's HW no further than its LEO, which maybe less than leader's log start
offset in fetch response, and then call
`replica.maybeIncrementLogStartOffset(leaderLogStartOffset)` which will throw
OffsetOutOfRangeException exception causing the fetcher thread to stop.
*Suggested fix:*
If the leader moves log start offset beyond fetched offset,
ReplicaManager#updateFollowerLogReadResults() should update the log read
result with OFFSET_OUT_OF_RANGE error, which will cause the follower to reset
fetch offset to leader's log start offset.
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