[jira] [Commented] (KAFKA-6481) Improving performance of the function ControllerChannelManager.addUpdateMetadataRequestForBrokers

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

    [ https://issues.apache.org/jira/browse/KAFKA-6481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16365030#comment-16365030 ] 

ASF GitHub Bot commented on KAFKA-6481:
---------------------------------------

junrao closed pull request #4472: KAFKA-6481: Improving performance of the function ControllerChannelManager.addUpd…
URL: https://github.com/apache/kafka/pull/4472
 
 
   

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diff --git a/core/src/main/scala/kafka/controller/ControllerChannelManager.scala b/core/src/main/scala/kafka/controller/ControllerChannelManager.scala
index e389821ad3b..547da2759cf 100755
--- a/core/src/main/scala/kafka/controller/ControllerChannelManager.scala
+++ b/core/src/main/scala/kafka/controller/ControllerChannelManager.scala
@@ -375,20 +375,14 @@ class ControllerBrokerRequestBatch(controller: KafkaController, stateChangeLogge
       }
     }
 
-    val filteredPartitions = {
-      val givenPartitions = if (partitions.isEmpty)
-        controllerContext.partitionLeadershipInfo.keySet
-      else
-        partitions
-      if (controller.topicDeletionManager.partitionsToBeDeleted.isEmpty)
-        givenPartitions
-      else
-        givenPartitions -- controller.topicDeletionManager.partitionsToBeDeleted
-    }
+    val givenPartitions = if (partitions.isEmpty)
+      controllerContext.partitionLeadershipInfo.keySet
+    else
+      partitions
 
     updateMetadataRequestBrokerSet ++= brokerIds.filter(_ >= 0)
-    filteredPartitions.foreach(partition => updateMetadataRequestPartitionInfo(partition, beingDeleted = false))
-    controller.topicDeletionManager.partitionsToBeDeleted.foreach(partition => updateMetadataRequestPartitionInfo(partition, beingDeleted = true))
+    givenPartitions.foreach(partition => updateMetadataRequestPartitionInfo(partition,
+      beingDeleted = controller.topicDeletionManager.partitionsToBeDeleted.contains(partition)))
   }
 
   def sendRequestsToBrokers(controllerEpoch: Int) {


 

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> Improving performance of the function ControllerChannelManager.addUpdateMetadataRequestForBrokers
> -------------------------------------------------------------------------------------------------
>
>                 Key: KAFKA-6481
>                 URL: https://issues.apache.org/jira/browse/KAFKA-6481
>             Project: Kafka
>          Issue Type: Improvement
>            Reporter: Lucas Wang
>            Assignee: Lucas Wang
>            Priority: Minor
>
> The function ControllerChannelManager.addUpdateMetadataRequestForBrokers should only process the partitions specified in the partitions parameter, i.e. the 2nd parameter, and avoid iterating through the set of partitions in TopicDeletionManager.partitionsToBeDeleted.
>  
> Here is why the current code can be a problem:
> The number of partitions-to-be-deleted stored in the field TopicDeletionManager.partitionsToBeDeleted can become quite large under certain scenarios. For instance, if a topic a0 has dead replicas, the topic a0 would be marked as ineligible for deletion, and its partitions will be retained in the field TopicDeletionManager.partitionsToBeDeleted for future retries.
>  With a large set of partitions in TopicDeletionManager.partitionsToBeDeleted, if some replicas in another topic a1 needs to be transitioned to OfflineReplica state, possibly because of a broker going offline, a call stack listed as following will happen on the controller, causing a iteration of the whole partitions-to-be-deleted set for every single affected partition.
>     controller.topicDeletionManager.partitionsToBeDeleted.foreach(partition => updateMetadataRequestPartitionInfo(partition, beingDeleted = true))
>      ControllerBrokerRequestBatch.addUpdateMetadataRequestForBrokers
>      ControllerBrokerRequestBatch.addLeaderAndIsrRequestForBrokers
>      _inside a for-loop for each partition_ 
>  ReplicaStateMachine.doHandleStateChanges
>  ReplicaStateMachine.handleStateChanges
>  KafkaController.onReplicasBecomeOffline
>  KafkaController.onBrokerFailure
> How to reproduce the problem:
>  1. Cretae a cluster with 2 brokers having id 1 and 2
>  2. Create a topic having 10 partitions and deliberately assign the replicas to non-existing brokers, i.e. 
>  ./bin/kafka-topics.sh --zookeeper localhost:2181 --create --topic a0 --replica-assignment `echo -n 3:4; for i in \`seq 9\`; do echo -n ,3:4; done`
> 3. Delete the topic and cause all of its partitions to be retained in the field TopicDeletionManager.partitionsToBeDeleted, since the topic has dead replicas, and is ineligible for deletion.
> ./bin/kafka-topics.sh --zookeeper localhost:2181 --delete --topic a0
> 4._Verify that the following log message shows up 10 times in the controller.log file, one line for each partition in topic a0: "Leader not yet assigned for partition [a0,..]. Skip sending UpdateMetadataRequest."_
> 5. Create another topic a1 also having 10 partitions, i.e.
>  ./bin/kafka-topics.sh --zookeeper localhost:2181 --create --topic a1 --replica-assignment `echo -n 1:2; for i in \`seq 9\`; do echo -n ,1:2; done`
> 6. Verify that the log message in step 4 appears *100 more* times (). This is because we have the following stack trace: 
>     addUpdateMetadataRequestForBrokers
>     addLeaderAndIsrRequestForBrokers
>     _inside a for-loop for each create response_   
> initializeLeaderAndIsrForPartitions
> In general, if n partitions have already been accumulated in the partitionsToBeDeleted variable, and a new topic is created with m partitions, m * n log messages above will be generated.
>  7. Kill the broker 2 and cause the replicas on broker 2 to be transitioned to OfflineReplica state on the controller.
>  8. Verify that the following log message in step 4 appears another *210* times. This is because
>     a. During controlled shutdown, the function KafkaController.doControlledShutdown calls replicaStateMachine.handleStateChanges to transition all the replicas on broker 2 to OfflineState. That in turn generates 100 (10 x 10) entries of the logs above.
>     b. When the broker zNode is gone in ZK, the function KafkaController.onBrokerFailure calls KafkaController.onReplicasBecomeOffline to transition all the replicas on broker 2 to OfflineState. And this again generates 100 (10 x 10) logs above.
>    c. At the bottom of the the function onReplicasBecomeOffline, it calls sendUpdateMetadataRequest (given the partitionsWithoutLeader is empty), which generates 10 logs, one for each partition in the a0 topic.
> In general, when we have n partitions accumulated in the variable partitionsToBeDeleted, and a broker with m partitions becomes offline, up to 2 * m * n + n logs could be generated.
> Performance improvement benchmark: if we perform the steps above with topic a0 having 5000 partitions, and topic a1 having 5000 partitions, when broker 2 goes down, it takes the controller ~4 minutes to go through controlled shutdown, detect the broker failure through zookeeper, and transition all replicas to OfflineReplica state. After applying the patch, the same process takes 23 seconds.
> The testing done:
> After applying the patch in this RB, I've verified that by going through the steps above, broker 2 going offline NO LONGER generates log entries for the a0 partitions.
> Also I've verified that topic deletion for topic a1 still works fine.



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