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Preferred leader election

As explained in Apache Kafka in Action

Preferred leader election is the selection of a partition's designated preferred replica as its leader when that replica is available and synchronized.

Preferred leader election restores a partition’s designated leader after recovery. The preferred replica is the first broker in the partition’s replica list and must be synchronized before taking leadership. section 5.3

Recovering a partition leader

If Broker 3 leads Partition 1 and fails, Kafka promotes an in-sync replica such as Broker 1. After Broker 3 rejoins and catches up, leadership remains with Broker 1 until automatic rebalancing occurs or an operator triggers a preferred election. 

$ kafka-topics.sh --create \
    --topic products.prices.changelog.replication-3 \
    --replication-factor 3 \
    --partitions 3 \
    --config min.insync.replicas=2 \
    --bootstrap-server localhost:9092
Created topic products.prices.changelog.replication-3.

Use kafka-leader-election.sh with --election-type=preferred to rebalance all topic partitions or target a specific topic. Avoid unclean elections except in extreme emergencies because out-of-sync replicas can lose data. section 5.3

How Apache Kafka in Action covers it

How deep it goes
Explains replica ordering, synchronization, automatic rebalancing, manual triggering, and the data-loss trade-off of unclean election.
Examples
Demonstrates Broker 3’s failure and recovery for Partition 1 using kafka-topics.sh and kafka-leader-election.sh.
What it assumes
Assumes familiarity with partition replication, replica ordering, leaders, followers, and in-sync replicas.
What you can do after
Operate Kafka leadership by triggering preferred elections and selecting targeted or cluster-wide scopes.
How it connects
Connects partition leaders with replicas, in-sync replicas, replication, leader-follower behavior, and unclean 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.