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https://issues.apache.org/jira/browse/KAFKA-5396?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16040367#comment-16040367
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Apurva Mehta commented on KAFKA-5396:
-------------------------------------
[~hachikuji] found the issue.
{noformat}
[2017-06-07 05:51:33,401] DEBUG Group concurrent_consumer fetching committed
offsets for partitions: [output-topic-1, output-topic-2, output-topic-0]
(org.apa
che.kafka.clients.consumer.internals.ConsumerCoordinator)
[2017-06-07 05:51:33,415] DEBUG Group concurrent_consumer has no committed
offset for partition output-topic-1
(org.apache.kafka.clients.consumer.internals.Co
nsumerCoordinator)
[2017-06-07 05:51:33,417] TRACE Sending ListOffsetRequest
(type=ListOffsetRequest, replicaId=-1, partitionTimestamps={output-topic-1=-2,
output-topic-2=-2}, m
inVersion=2) to broker knode08:9092 (id: 1 rack: null)
(org.apache.kafka.clients.consumer.internals.Fetcher)
[2017-06-07 05:51:33,451] DEBUG Handling ListOffsetResponse response for
output-topic-1. Fetched offset 0, timestamp -1
(org.apache.kafka.clients.consumer.int
ernals.Fetcher)
[2017-06-07 05:51:33,452] DEBUG Resetting offset for partition output-topic-1
to offset 0. (org.apache.kafka.clients.consumer.internals.Fetcher)
{noformat}
Since we don't commit offsets, the positions are reset during the group
rebalance. This happens just before the reset above:
{noformat}
[2017-06-07 05:51:33,145] INFO [GroupCoordinator 3]: Preparing to restabilize
group concurrent_consumer with old generation 2
(kafka.coordinator.group.GroupCoordinator)
{noformat}
> Consumer reading uninterrupted 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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