[GitHub] [kafka] junrao commented on a change in pull request #8524: KAFKA-9866: Avoid election for topics where preferred leader is not in ISR

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junrao commented on a change in pull request #8524:
URL: https://github.com/apache/kafka/pull/8524#discussion_r416164863



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File path: core/src/main/scala/kafka/controller/KafkaController.scala
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@@ -1068,12 +1068,23 @@ class KafkaController(val config: KafkaConfig,
         val candidatePartitions = topicsNotInPreferredReplica.keys.filter(tp 
=> controllerContext.isReplicaOnline(leaderBroker, tp) &&
           controllerContext.partitionsBeingReassigned.isEmpty &&
           !topicDeletionManager.isTopicQueuedUpForDeletion(tp.topic) &&
-          controllerContext.allTopics.contains(tp.topic))
+          controllerContext.allTopics.contains(tp.topic) &&
+          canPreferredReplicaBeLeader(tp)
+       )
         onReplicaElection(candidatePartitions.toSet, ElectionType.PREFERRED, 
AutoTriggered)
       }
     }
   }
 
+  private def canPreferredReplicaBeLeader(tp: TopicPartition): Boolean = {
+    val assignment = controllerContext.partitionReplicaAssignment(tp)
+    val liveReplicas = assignment.filter(replica => 
controllerContext.isReplicaOnline(replica, tp))

Review comment:
       Good point. We can get rid of the isReplicaOnline() check in the caller. 
@leonardge : Could you summit a followup minor PR?




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