[
https://issues.apache.org/jira/browse/KAFKA-2334?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15032642#comment-15032642
]
Guozhang Wang commented on KAFKA-2334:
--------------------------------------
[~jinxing6...@126.com] The problem with this scenario is not related to
LeaderAndISRRequest but in follower's FetchResponse, which will make the
follower to update HW according to the returned value:
https://github.com/apache/kafka/blob/trunk/core/src/main/scala/kafka/server/ReplicaFetcherThread.scala#L120
If the Fetch Response is not returned from the previous leader, then this
follower will not update its HW and when itself becoming the new leader, the HW
will effectively "go back" from the consumer point of view.
> Prevent HW from going back during leader failover
> --------------------------------------------------
>
> Key: KAFKA-2334
> URL: https://issues.apache.org/jira/browse/KAFKA-2334
> Project: Kafka
> Issue Type: Bug
> Components: replication
> Affects Versions: 0.8.2.1
> Reporter: Guozhang Wang
> Assignee: Neha Narkhede
> Fix For: 0.10.0.0
>
>
> Consider the following scenario:
> 0. Kafka use replication factor of 2, with broker B1 as the leader, and B2 as
> the follower.
> 1. A producer keep sending to Kafka with ack=-1.
> 2. A consumer repeat issuing ListOffset request to Kafka.
> And the following sequence:
> 0. B1 current log-end-offset (LEO) 0, HW-offset 0; and same with B2.
> 1. B1 receive a ProduceRequest of 100 messages, append to local log (LEO
> becomes 100) and hold the request in purgatory.
> 2. B1 receive a FetchRequest starting at offset 0 from follower B2, and
> returns the 100 messages.
> 3. B2 append its received message to local log (LEO becomes 100).
> 4. B1 receive another FetchRequest starting at offset 100 from B2, knowing
> that B2's LEO has caught up to 100, and hence update its own HW, and
> satisfying the ProduceRequest in purgatory, and sending the FetchResponse
> with HW 100 back to B2 ASYNCHRONOUSLY.
> 5. B1 successfully sends the ProduceResponse to the producer, and then fails,
> hence the FetchResponse did not reach B2, whose HW remains 0.
> From the consumer's point of view, it could first see the latest offset of
> 100 (from B1), and then see the latest offset of 0 (from B2), and then the
> latest offset gradually catch up to 100.
> This is because we use HW to guard the ListOffset and
> Fetch-from-ordinary-consumer.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
