[jira] [Commented] (KAFKA-955) After a leader change, messages sent with ack=0 are lost

["Jun Rao (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/KAFKA-955?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13756692#comment-13756692 ] 

Jun Rao commented on KAFKA-955:
-------------------------------

Thanks for patch v7. A couple of more comments.

70. There is a long standing bug in ProducerRequest.handleError(). If ack=0, we shouldn't send a response when the broker hits an unexpected error. We should either close the socket connection or send no response. Not sure which one is better.

71. A minor issue. The following comment in RequestChannel is a bit confusing. It sounds like that it needs to read more data from network to complete this request, but it is not.
  /** No operation to take for the request, need to read more over the network */
  def noOperation(processor: Int, request: RequestChannel.Request) {

                
> 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
>    Affects Versions: 0.8
>            Reporter: Jason Rosenberg
>            Assignee: Guozhang Wang
>             Fix For: 0.8
>
>         Attachments: KAFKA-955.v1.patch, KAFKA-955.v1.patch, KAFKA-955.v2.patch, KAFKA-955.v3.patch, KAFKA-955.v4.patch, KAFKA-955.v5.patch, KAFKA-955.v6.patch, KAFKA-955.v7.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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