Jason Gustafson created KAFKA-6134:
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Summary: 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
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:
!Screen Shot 2017-10-26 at 3.05.40 PM.png|thumbnail!.
>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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