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https://issues.apache.org/jira/browse/FLINK-4702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15529448#comment-15529448
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ASF GitHub Bot commented on FLINK-4702:
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Github user tzulitai commented on the issue:
https://github.com/apache/flink/pull/2559
Just had a look at the API of `commitAsync`, and it seems like the
committed offsets back to Kafka through this API (likewise for `commitSync`)
need to be `lastProcessedMessageOffset + 1`
([https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#commitAsync(java.util.Map,%20org.apache.kafka.clients.consumer.OffsetCommitCallback)](https://kafka.apache.org/090/javadoc/org/apache/kafka/clients/consumer/KafkaConsumer.html#commitAsync(java.util.Map,%20org.apache.kafka.clients.consumer.OffsetCommitCallback))).
This mainly effects that when starting from group offsets in Kafka,
`FlinkKafkaConsumer09` currently starts from the wrong offset. There's a
separate JIRA for this bug:
[FLINK-4618](https://issues.apache.org/jira/browse/FLINK-4618).
Another contributor had already picked up FLINK-4618, so I'd say it's ok to
leave this PR as it is. I'll help check on FLINK-4618 progress and make sure it
gets merged after this PR.
Minus the above, this looks good to me. +1
> Kafka consumer must commit offsets asynchronously
> -------------------------------------------------
>
> Key: FLINK-4702
> URL: https://issues.apache.org/jira/browse/FLINK-4702
> Project: Flink
> Issue Type: Bug
> Components: Kafka Connector
> Affects Versions: 1.1.2
> Reporter: Stephan Ewen
> Assignee: Stephan Ewen
> Priority: Blocker
> Fix For: 1.2.0, 1.1.3
>
>
> The offset commit calls to Kafka may occasionally take very long.
> In that case, the {{notifyCheckpointComplete()}} method blocks for long and
> the KafkaConsumer cannot make progress and cannot perform checkpoints.
> Kafka 0.9+ have methods to commit asynchronously.
> We should use those and make sure no more than one commit is concurrently in
> progress, to that commit requests do not pile up.
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