[jira] [Commented] (ROCKETMQ-67) Consistent Hash allocate strategy support

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/ROCKETMQ-67?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16038062#comment-16038062 ] 

ASF GitHub Bot commented on ROCKETMQ-67:
----------------------------------------

Github user asfgit closed the pull request at:

    https://github.com/apache/incubator-rocketmq/pull/67


> Consistent Hash allocate strategy support
> -----------------------------------------
>
>                 Key: ROCKETMQ-67
>                 URL: https://issues.apache.org/jira/browse/ROCKETMQ-67
>             Project: Apache RocketMQ
>          Issue Type: New Feature
>          Components: rocketmq-client
>            Reporter: Jaskey Lam
>            Assignee: Jaskey Lam
>             Fix For: 4.1.0-incubating
>
>
> For now, the average allocate strategy is very sensitive when clients register and unrigister.
> A Consistent Hash allocate strategy option is valueable for the developers who care more about latency stabilization and messages duplication.
> Intentions: 
> The default AllocateMessageQueueStrategy is averaging strategy which allocate queue to consumer as evenly as possible. Whenever queues numbers or consumer numbers changed, say a new consumer starts or an old consumer shutdowns, a rehashing will be triggered then almost all consumer suffered from this that they will rebalance to drop old queues and get new queues.
> And that will cause
> message latency from producer to consumer increases at the moment when consumer/queue numbers change, even when they scale up.
> messages will be duplicated significantly since the offset may not be persisted to broker and that queue is assigned to another consumer to pull messages from.
> This is especially significant when they have tens of consumer instances and scale-up or deployment is often.
> Consistent Hash strategy to allocate queue is a good choice for these users.



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