[jira] [Created] (KAFKA-8359) Reconsider default for leader imbalance percentage

["Dhruvil Shah (JIRA)" <ji...@apache.org>]

Dhruvil Shah created KAFKA-8359:
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             Summary: Reconsider default for leader imbalance percentage
                 Key: KAFKA-8359
                 URL: https://issues.apache.org/jira/browse/KAFKA-8359
             Project: Kafka
          Issue Type: Improvement
            Reporter: Dhruvil Shah


By default, the leader imbalance ratio is 10%. This means that the controller won't trigger preferred leader election for a broker unless the ratio of the number of partitions a broker is the current leader of and the number of partitions it is the preferred leader of is off by more than 10%. The problem is when a broker is catching up after a restart, the smallest topics tend to catch up first and the largest ones later, so the 10% remaining difference may not be proportional to the broker's load. To keep better balance in the cluster, we should consider setting `leader.imbalance.per.broker.percentage=0` by default so that the preferred leaders are always elected.



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