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https://issues.apache.org/jira/browse/KAFKA-9491?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jason Gustafson resolved KAFKA-9491.
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Resolution: Fixed
> Fast election during reassignment can lead to replica fetcher failures
> ----------------------------------------------------------------------
>
> Key: KAFKA-9491
> URL: https://issues.apache.org/jira/browse/KAFKA-9491
> Project: Kafka
> Issue Type: Bug
> Reporter: Jason Gustafson
> Assignee: Jason Gustafson
> Priority: Major
> Fix For: 2.5.0, 2.4.1
>
>
> We have observed an unusual case in which a new replica became leader before
> it had received an initial high watermark from the previous leader. This
> resulted in an OffsetOutOfRangeException being raised while looking up the
> segment position of the uninitialized high watermark, since it was lower than
> the log start offset. The error was raised while handle the fetch request
> from one of the followers and prevented it from making progress.
> {code}
> org.apache.kafka.common.errors.OffsetOutOfRangeException: Received request
> for offset 0 for partition foo-0, but we only have log segments in the range
> 20 to 20.
> {code}
> Here is what we have observed from the logs. The initial state of the
> partition for the relevant sequence of events is the following:
> Initial state: replicas=[4,1,2,3], leader=1, isr=[1,2,3], adding=[4],
> removing=[1], epoch=5, logStartOffset=20, logEndOffset=20
> We see the following events:
> t0: Replica 4 becomes follower and initializes log with hw=0, logStartOffset=0
> t1: Replica 4 begins fetching from offset 0 and receives an out of range error
> t2: After a ListOffset request to the leader, replica 4 initializes
> logStartOffset to 20.
> t3: Replica 4 sends fetch request to the leader at start offset 20
> t4: Upon receiving the fetch request, the leader adds 4 to the ISR (i.e.
> isr=[1,2,3,4])
> t5: The controller notices the ISR addition and makes 4 the leader since 1 is
> to be removed and 4 is the new preferred leader
> t6: Replica 4 stops fetchers and becomes leader
> t7: We begin seeing the out of range errors as the other replicas begin
> fetching from 4.
> We know from analysis of a heap dump from broker 4, that the high watermark
> was still set to 0 some time after it had become leader. We also know that
> broker 1 was under significant load. The time between events t4 and t6 was
> less than 10ms. We don't know when the fetch response sent at t3 returned to
> broker 4, but we speculate that it happened after t6 due to the heavy load on
> the leader, which is why broker 4 had an uninitialized high watermark.
> A more mundane possibility is that there is a bug in the fetch session logic
> and the partition was simply not included in the fetch response. However, the
> code appears to anticipate this case. When a partition has an error, we set
> the cached high watermark to -1 to ensure that it gets updated as soon as the
> error clears.
> Regardless how we got there, the fix should be straightforward. When a broker
> becomes leader, it should ensure its high watermark is at least as large as
> the log start offset.
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