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https://issues.apache.org/jira/browse/KAFKA-3788?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arkadiusz Firus resolved KAFKA-3788.
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Resolution: Not A Problem
> Potential message lost when switching to new segment
> ----------------------------------------------------
>
> Key: KAFKA-3788
> URL: https://issues.apache.org/jira/browse/KAFKA-3788
> Project: Kafka
> Issue Type: Bug
> Components: log
> Affects Versions: 0.9.0.0, 0.9.0.1, 0.10.0.0
> Reporter: Arkadiusz Firus
> Assignee: Jay Kreps
> Priority: Minor
> Labels: easyfix
> Original Estimate: 1h
> Remaining Estimate: 1h
>
> If a new segment is needed method roll() from class kafka.log.Log is invoked.
> It prepares new segment and schedules _asynchronous_ flush of the previous
> segment.
> Asynchronous call can lead to a problematic situation. As far as I know
> neither Linux nor Windows guarantees that the order of files persisted to
> disk will be the same as the order of writes to files. This means that
> records from the new segment can be flushed before the old ones which in case
> of power outage can lead to gaps between records.
> Changing asynchronous invocation to synchronous one will solve the problem
> because we have guarantee that all records from the previous segment will be
> persisted to hard drive before we write any record to the new segment.
> I am guessing that asynchronous invocation was chosen to increase performance
> but switching between segments is not so often. So it is not a big gain.
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