[jira] [Resolved] (KAFKA-6134) High memory usage on controller during partition reassignment

["Jason Gustafson (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-6134?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jason Gustafson resolved KAFKA-6134.
------------------------------------
    Resolution: Fixed

> High memory usage on controller during partition reassignment
> -------------------------------------------------------------
>
>                 Key: KAFKA-6134
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6134
>             Project: Kafka
>          Issue Type: Bug
>          Components: controller
>    Affects Versions: 0.11.0.0, 0.11.0.1
>            Reporter: Jason Gustafson
>            Assignee: Jason Gustafson
>            Priority: Critical
>              Labels: regression
>             Fix For: 1.0.0, 0.11.0.2
>
>         Attachments: Screen Shot 2017-10-26 at 3.05.40 PM.png
>
>
> We've had a couple users reporting spikes in memory usage when the controller is performing partition reassignment in 0.11. After investigation, we found that the controller event queue was using most of the retained memory. In particular, we found several thousand {{PartitionReassignment}} objects, each one containing one fewer partition than the previous one (see the attached image).
> From the code, it seems clear why this is happening. We have a watch on the partition reassignment path which adds the {{PartitionReassignment}} object to the event queue:
> {code}
>   override def handleDataChange(dataPath: String, data: Any): Unit = {
>     val partitionReassignment = ZkUtils.parsePartitionReassignmentData(data.toString)
>     eventManager.put(controller.PartitionReassignment(partitionReassignment))
>   }
> {code}
> In the {{PartitionReassignment}} event handler, we iterate through all of the partitions in the reassignment. After we complete reassignment for each partition, we remove that partition and update the node in zookeeper. 
> {code}
>     // remove this partition from that list
>     val updatedPartitionsBeingReassigned = partitionsBeingReassigned - topicAndPartition
>     // write the new list to zookeeper
>   zkUtils.updatePartitionReassignmentData(updatedPartitionsBeingReassigned.mapValues(_.newReplicas))
> {code}
> This triggers the handler above which adds a new event in the queue. So what you get is an n^2 increase in memory where n is the number of partitions.



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