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https://issues.apache.org/jira/browse/CAMEL-13339?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16797790#comment-16797790
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Ramu commented on CAMEL-13339:
------------------------------
you are very welcome to send a PR. We love contributions
https://github.com/apache/camel/blob/master/CONTRIBUTING.md
> StateRepository implemented to save offset state outside Kafka, message loss
> occurs upon partition revoke
> ---------------------------------------------------------------------------------------------------------
>
> Key: CAMEL-13339
> URL: https://issues.apache.org/jira/browse/CAMEL-13339
> Project: Camel
> Issue Type: Bug
> Components: camel-kafka
> Affects Versions: 2.23.0
> Reporter: Viswa Ramamoorthy
> Priority: Major
>
> Current implementation of
> org.apache.camel.component.kafka.KafkaConsumer.KafkaFetchRecords's
> onPartitionsRevoked, uses
> org.apache.kafka.clients.consumer.KafkaConsumer.position(partition). This
> approach causes message loss when multiple processes listening to same topic
> for point to point messaging (like a QUEUE) type implementation.
>
> Issue is noticed when partition gets assigned and then gets revoked in quick
> succession. Upon partition assignment, say at the beginning of processing
> offset is set to 0, and say there was no poll for this partition (may be due
> to earlier poll brought in bunch of records and they are still being
> processed). Subsequently, say partition got revoked, before polling.
> In this case, as onPartitionsRevoked looks at
> org.apache.kafka.clients.consumer.KafkaConsumer.position(partition) to save
> offset state and so 0 gets saved in this case in StateRepository
> implementation. When the same partition get assigned again,
> StateRepository.getState returns 0. Since Camel KafkaConsumer treats this as
> last processed offset, it adds 1 to it moving pointer to offset 1. Because of
> this, message at offset 0 never gets processed.
>
> Two fixes might be needed
> # a) onPartitionsRevoked should look at last processed offset (possibly
> store 'last processed offset' for each topic/partition in a memory map) and
> use it to save offset
> # b) Currently onPartitionsRevoked just saves offset state when an
> implementation of StateRepository configured. Ideally it should call
> KafkaFetchRecords.commitOffset so commitSync call goes through when partition
> revoked and no StateRepository implementation configured
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