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https://issues.apache.org/jira/browse/KAFKA-2139?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14507480#comment-14507480
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Jiangjie Qin commented on KAFKA-2139:
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Sure, I will be glad to write a wiki and put the stuff I'm thinking in it. I
can do it this weekend. It will be a significant change and definitely needs a
lot of discussions.
In term of this proposal, the message from the same TCP connection will still
be processed in order (Originally I was proposing to add controller message to
the queue head, that won't work). Current proposal is to have a separate queue
for controller requests so the requests from controller to broker connection
are still in order. I like the idea to prioritize messages at network layer and
probably we can do that.
> Add a separate controller messge queue with higher priority on broker side
> ---------------------------------------------------------------------------
>
> Key: KAFKA-2139
> URL: https://issues.apache.org/jira/browse/KAFKA-2139
> Project: Kafka
> Issue Type: Improvement
> Reporter: Jiangjie Qin
> Assignee: Jiangjie Qin
>
> This ticket is supposed to be working together with KAFKA-2029.
> There are two issues with current controller to broker messages.
> 1. On the controller side the message are sent without synchronization.
> 2. On broker side the controller messages share the same queue as client
> messages.
> The problem here is that brokers process the controller messages for the same
> partition at different times and the variation could be big. This causes
> unnecessary data loss and prolong the preferred leader election / controlled
> shutdown/ partition reassignment, etc.
> KAFKA-2029 was trying to add a boundary between messages for different
> partitions. For example, before leader migration for previous partition
> finishes, the leader migration for next partition won't begin.
> This ticket is trying to let broker process controller messages faster. So
> the idea is have separate queue to hold controller messages, if there are
> controller messages, KafkaApi thread will first take care of those messages,
> otherwise it will proceed messages from clients.
> Those two tickets are not ultimate solution to current controller problems,
> but just mitigate them with minor code changes. Moving forward, we still need
> to think about rewriting controller in a cleaner way.
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