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Leader rebalancing

As explained in Apache Kafka in Action

Leader rebalancing is the redistribution of Kafka partition leadership to restore preferred leader assignments or balance broker load.

Leader rebalancing restores a partition’s preferred leader after a broker returns or leadership has shifted. A returning broker first synchronizes as an in-sync follower; it may later reclaim leadership automatically or require a manual election. section 5.3

Use the following operational sequence:

  • Confirm that the recovered broker has rejoined the ISR and that replicas are synchronized. section 5.3
  • Trigger preferred elections with kafka-leader-election.sh when automatic rebalancing is not configured or has not occurred. section 5.3
  • Avoid unclean elections except in an extreme emergency, because an out-of-sync replica may lack messages and cause data loss. section 5.3

Restoring a preferred leader

For products.prices.changelog.replication-3, Broker 3 returns and becomes an ISR follower for Partition 1. Running kafka-leader-election.sh with --election-type=preferred and --all-topic-partitions moves leadership back to Broker 3.

How Apache Kafka in Action covers it

How deep it goes
Explains recovery, ISR synchronization, automatic timing, manual election, and unclean-election risk without detailing controller internals.
Examples
Demonstrates Broker 3 recovering, rejoining the ISR, and reclaiming Partition 1 through a preferred election.
What it assumes
Assumes familiarity with Kafka brokers, partitions, replicas, leaders, followers, and ISR membership.
What you can do after
Operate leader restoration with kafka-leader-election.sh and distinguish safe preferred elections from risky unclean elections.
How it connects
Connects partition leadership with replication, replicas, in-sync replicas, broker recovery, and leader election.
Cover of Apache Kafka in Action
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This explainer was generated by Manning's knowledge graph from the text of Apache Kafka in Action. The section links point to the parts of the book it draws on.