[jira] [Resolved] (KAFKA-9866) Do not attempt to elect preferred leader replicas which are outside ISR

["Jun Rao (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KAFKA-9866?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jun Rao resolved KAFKA-9866.
----------------------------
    Fix Version/s: 2.6.0
       Resolution: Fixed

Merged the PR to trunk.

> Do not attempt to elect preferred leader replicas which are outside ISR
> -----------------------------------------------------------------------
>
>                 Key: KAFKA-9866
>                 URL: https://issues.apache.org/jira/browse/KAFKA-9866
>             Project: Kafka
>          Issue Type: Improvement
>            Reporter: Stanislav Kozlovski
>            Assignee: Wang Ge
>            Priority: Minor
>             Fix For: 2.6.0
>
>
> The controller automatically triggers a preferred leader election every N minutes. It tries to elect all preferred leaders of partitions without doing some basic checks like whether the leader is in sync.
> This leads to a multitude of errors which cause confusion:
> {code:java}
> April 14th 2020, 17:01:11.015	[Controller id=0] Partition TOPIC-9 failed to complete preferred replica leader election to 1. Leader is still 0{code}
> {code:java}
> April 14th 2020, 17:01:11.002	[Controller id=0] Error completing replica leader election (PREFERRED) for partition TOPIC-9
> kafka.common.StateChangeFailedException: Failed to elect leader for partition TOPIC-9 under strategy PreferredReplicaPartitionLeaderElectionStrategy {code}
> It would be better if the Controller filtered out some of these elections, not attempt them at all and maybe log an aggregate INFO-level log



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