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https://issues.apache.org/jira/browse/KAFKA-573?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13475966#comment-13475966
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John Fung commented on KAFKA-573:
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If ack is set to 1, we actually don't guarantee no data loss. This is because
when the client receives an ack, data is only guaranteed to be in the leader,
but not necessarily in other replicas. So, if a leader is bounced, some acked
data could be lost.
Nevertheless, merged checksums should still match among all replicas.
> System Test : Leader Failure Log Segment Checksum Mismatched When
> request-num-acks is 1
> ---------------------------------------------------------------------------------------
>
> Key: KAFKA-573
> URL: https://issues.apache.org/jira/browse/KAFKA-573
> Project: Kafka
> Issue Type: Bug
> Reporter: John Fung
> Attachments: acks1_leader_failure_data_loss.tar.gz,
> kafka-573-reproduce-issue.patch
>
>
> • Test Description:
> 1. Start a 3-broker cluster as source
> 2. Send messages to source cluster
> 3. Find leader and terminate it (kill -15)
> 4. Start the broker again
> 5. Start a consumer to consume data
> 6. Compare the MessageID in the data between producer log and consumer log.
> • Issue: There will be data loss if request-num-acks is set to 1.
> • To reproduce this issue, please do the followings:
> 1. Download the latest 0.8 branch
> 2. Apply the patch attached to this JIRA
> 3. Build kafka by running "./sbt update package"
> 4. Execute the test in directory "system_test" : "python -B
> system_test_runner.py"
> 5. This test will execute testcase_2 with the following settings:
> Replica factor : 3
> No. of partitions : 1
> No. of bouncing : 1
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