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https://issues.apache.org/jira/browse/KAFKA-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apurva Mehta updated KAFKA-5396:
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Attachment: KAFKA-5396.tar.gz
> Consumer reading from beginning of log can read the same message multiple
> times.
> --------------------------------------------------------------------------------
>
> Key: KAFKA-5396
> URL: https://issues.apache.org/jira/browse/KAFKA-5396
> Project: Kafka
> Issue Type: Bug
> Reporter: Apurva Mehta
> Attachments: KAFKA-5396.tar.gz
>
>
> I noticed this when running the transactions system test with hard broker
> bounces. We have a consumer in READ_COMMITTED mode reading from the tail of
> the log as the writes are appended.
> This test has failed once because the concurrent consumer returned duplicate
> data. The actual log has no duplicates, so the problem is in the consumer.
> One of the duplicate values is '0', and is at offset 250 in output-topic-1.
> The first time it is read, we see the following.
> {noformat}
> [2017-06-07 05:50:34,601] TRACE Returning fetched records at offset 0 for
> assigned partition output-topic-0 and update position to 250
> (org.apache.kafka.clients.consumer.internals.Fetcher)
> [2017-06-07 05:50:34,602] TRACE Preparing to read 2967 bytes of data for
> partition output-topic-1 with offset 250
> (org.apache.kafka.clients.consumer.internals.Fetcher)
> [2017-06-07 05:50:34,602] TRACE Updating high watermark for partition
> output-topic-1 to 502 (org.apache.kafka.clients.consumer.internals.Fetcher)
> [2017-06-07 05:50:34,613] TRACE Returning fetched records at offset 250 for
> assigned partition output-topic-1 and update position to 500
> (org.apache.kafka.clients.consumer.internals.Fetcher)
> {noformat}
> The next time it is read, we see this
> {noformat}
> [2017-06-07 05:51:36,386] TRACE Preparing to read 169858 bytes of data for
> partition output-topic-1 with offset 0
> (org.apache.kafka.clients.consumer.internals.Fetcher)
> [2017-06-07 05:51:36,389] TRACE Updating high watermark for partition
> output-topic-1 to 13053 (org.apache.kafka.clients.consumer.internals.Fetcher)
> [2017-06-07 05:51:36,391] TRACE Returning fetched records at offset 0 for
> assigned partition output-topic-1 and update position to 500
> (org.apache.kafka.clients.consumer.internals.Fetcher)
> {noformat}
> For some reason, the fetcher re-sent the data from offset 0, an reset the
> position to 500.
> This is the plain consumer doing 'poll' in a loop until it is killed. So this
> position reset is puzzling.
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