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https://issues.apache.org/jira/browse/KAFKA-10339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17171612#comment-17171612
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Ning Zhang commented on KAFKA-10339:
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thanks for the input. I think that sounds a working plan. Here is my follow-up
thoughts
_"when MirrorSourceTask starts, it loads initial offsets from
__consumer_offsets on the target cluster."_
As the consumer is configured to pull data from source cluster, I am thinking
we probably need to:
(1) add a new API (called "Map<TopicPartition, Long> loadOffsets()") to
[SinkTask.java|https://github.com/apache/kafka/blob/trunk/connect/api/src/main/java/org/apache/kafka/connect/sink/SinkTask.java]
(2) in MirrorSinkTask.java, implement/override loadOffsets() to supply the
consumer offsets loaded from target cluster.
(3) in
[WorkerSinkTask.java|https://github.com/apache/kafka/blob/trunk/connect/runtime/src/main/java/org/apache/kafka/connect/runtime/WorkerSinkTask.java#L295],
when initialize the consumer, if `task.loadOffsets()` returns non empty, use
the returned offsets as the starting point.
_"in addition, we call addOffsetsToTransaction in order to commit offsets to
the "fake" consumer group on the target cluster."_
I fully agree with the "fake" consumer group on the target cluster. I am
thinking if "addOffsetsToTransaction" has been taken care by
*producer.sendOffsetsToTransaction(offsetsMap, consumerGroupId);*?
> MirrorMaker2 Exactly-once Semantics
> -----------------------------------
>
> Key: KAFKA-10339
> URL: https://issues.apache.org/jira/browse/KAFKA-10339
> Project: Kafka
> Issue Type: New Feature
> Components: KafkaConnect
> Reporter: Ning Zhang
> Assignee: Ning Zhang
> Priority: Major
> Labels: needs-kip
>
> MirrorMaker2 is currently implemented on Kafka Connect Framework, more
> specifically the Source Connector / Task, which do not provide exactly-once
> semantics (EOS) out-of-the-box, as discussed in
> https://github.com/confluentinc/kafka-connect-jdbc/issues/461,
> https://github.com/apache/kafka/pull/5553,
> https://issues.apache.org/jira/browse/KAFKA-6080 and
> https://issues.apache.org/jira/browse/KAFKA-3821. Therefore MirrorMaker2
> currently does not provide EOS.
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