[GitHub] [kafka] hachikuji commented on a change in pull request #9302: KAFKA-10149: Allow auto preferred leader election when partitions are reassigning

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hachikuji commented on a change in pull request #9302:
URL: https://github.com/apache/kafka/pull/9302#discussion_r491094781



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File path: core/src/main/scala/kafka/controller/KafkaController.scala
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@@ -1067,10 +1067,7 @@ class KafkaController(val config: KafkaConfig,
       // check ratio and if greater than desired ratio, trigger a rebalance for the topic partitions
       // that need to be on this broker
       if (imbalanceRatio > (config.leaderImbalancePerBrokerPercentage.toDouble / 100)) {
-        // do this check only if the broker is live and there are no partitions being reassigned currently
-        // and preferred replica election is not in progress
         val candidatePartitions = topicsNotInPreferredReplica.keys.filter(tp =>
-          controllerContext.partitionsBeingReassigned.isEmpty &&

Review comment:
       It's a good question. During a reassignment, the adding replicas are always listed first which means the preferred leader is among the target replicas. My take is that we want to move the leadership onto the new preferred leader as soon as possible since the whole point of the reassignment is to take load off the removing replicas.




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