Ma Tianchi created KAFKA-5319:
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Summary: Add a tool to make cluster replica and leader balance
Key: KAFKA-5319
URL: https://issues.apache.org/jira/browse/KAFKA-5319
Project: Kafka
Issue Type: Improvement
Components: admin
Affects Versions: 0.10.2.1
Reporter: Ma Tianchi
Attachments: ClusterBalanceCommand.scala
When a new broker is added to cluster,there is not any topics in the new
broker.When we use console command to create a topic without
'replicaAssignmentOpt',Kafka use AdminUtils.assignReplicasToBrokers to get
replicaAssignment.Even though it is balance at the creating time if the cluster
never change,with more and more brokers added to cluster the replica balanced
will become not well. We also can use 'kafka-reassign-partitions.sh' to balance
,but the big amount of topics make it not easy.And at the topic created time ,
Kafka choose a PreferredReplicaLeader which be put at the first position of
the AR to make leader balance.But the balance will be destroyed when cluster
changed.Using 'kafka-reassign-partitions.sh' to make partition reassignment
may be also destroy the leader balance ,because user can change the AR of the
partition . It may be not balanced , but Kafka believe cluster leader balance
is well with every leaders is the first on at AR.
So we create a tool to make the number of replicas and number of leaders on
every brokers is balanced.It uses a algorithm to get a balanced replica and
leader reassignment,then uses ReassignPartitionsCommand to real balance the
cluster.
It can be used to make balance when cluster added brokers or cluster is not
balanced .It does not deal with moving replicas of a dead broker to an alive
broker,it only makes replicas and leaders on alive brokers is balanced.
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