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https://issues.apache.org/jira/browse/KAFKA-955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13746791#comment-13746791
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Guozhang Wang commented on KAFKA-955:
-------------------------------------
Hello Magnus,
1. Under Ack=0, the producer does not expect any responses for produce request,
and it does not listen to any possible connections from the producer either. So
actively sending MetadataResponse would not work: producers are only expecting
MetadataResponse when they send MetadataRequest.
2. When we close the socket, producer would be notified and try to refresh
their Metadata and retry. Since by default each produce request will be retried
multiple times before it is got dropped, the current approach would not cause
lost messages.
> After a leader change, messages sent with ack=0 are lost
> --------------------------------------------------------
>
> Key: KAFKA-955
> URL: https://issues.apache.org/jira/browse/KAFKA-955
> Project: Kafka
> Issue Type: Bug
> Reporter: Jason Rosenberg
> Assignee: Guozhang Wang
> Attachments: KAFKA-955.v1.patch, KAFKA-955.v1.patch,
> KAFKA-955.v2.patch, KAFKA-955.v3.patch
>
>
> If the leader changes for a partition, and a producer is sending messages
> with ack=0, then messages will be lost, since the producer has no active way
> of knowing that the leader has changed, until it's next metadata refresh
> update.
> The broker receiving the message, which is no longer the leader, logs a
> message like this:
> Produce request with correlation id 7136261 from client on partition
> [mytopic,0] failed due to Leader not local for partition [mytopic,0] on
> broker 508818741
> This is exacerbated by the controlled shutdown mechanism, which forces an
> immediate leader change.
> A possible solution to this would be for a broker which receives a message,
> for a topic that it is no longer the leader for (and if the ack level is 0),
> then the broker could just silently forward the message over to the current
> leader.
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