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https://issues.apache.org/jira/browse/KAFKA-6718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16415967#comment-16415967
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Guozhang Wang commented on KAFKA-6718:
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[~_deepakgoyal] thanks for creating the KIP! I've assigned the JIRA to you.
About the KIP itself, please note that if you are enhancing the rebalance
protocol to encode the rack id information, these two KIPs are correlated and
I'd recommend you read about them first:
Any protocol changes will need to consider a smooth upgrade path:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-268%3A+Simplify+Kafka+Streams+Rebalance+Metadata+Upgrade
We'd like to encode some other information into the metadata to enhance
partition assignor's workload balance awareness:
https://cwiki.apache.org/confluence/display/KAFKA/KIP-262%3A+Metadata+should+include+number+of+state+stores+for+task
> Rack Aware Replica Task Assignment for Kafka Streams
> ----------------------------------------------------
>
> Key: KAFKA-6718
> URL: https://issues.apache.org/jira/browse/KAFKA-6718
> Project: Kafka
> Issue Type: New Feature
> Components: streams
> Affects Versions: 1.1.0
> Reporter: Deepak Goyal
> Assignee: Deepak Goyal
> Priority: Major
>
> |Machines in data centre are sometimes grouped in racks. Racks provide
> isolation as each rack may be in a different physical location and has its
> own power source. When tasks are properly replicated across racks, it
> provides fault tolerance in that if a rack goes down, the remaining racks can
> continue to serve traffic.
>
> This feature is already implemented at Kafka
> [KIP-36|https://cwiki.apache.org/confluence/display/KAFKA/KIP-36+Rack+aware+replica+assignment]
> but we needed similar for task assignments at Kafka Streams Application
> layer.
>
> This features enables replica tasks to be assigned on different racks for
> fault-tolerance.
> NUM_STANDBY_REPLICAS = x
> totalTasks = x+1 (replica + active)
> # If there are no rackID provided: Cluster will behave rack-unaware
> # If same rackId is given to all the nodes: Cluster will behave rack-unaware
> # If (totalTasks >= number of racks), then Cluster will be rack aware i.e.
> each replica task is each assigned to a different rack.
> # Id (totalTasks < number of racks), then it will first assign tasks on
> different racks, further tasks will be assigned to least loaded node, cluster
> wide.|
> We have added another config in StreamsConfig called "RACK_ID_CONFIG" which
> helps StickyPartitionAssignor to assign tasks in such a way that no two
> replica tasks are on same rack if possible.
> Post that it also helps to maintain stickyness with-in the rack.|
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