kafka集群扩容后的topic分区迁移
kafka-reassign-partitions.sh是kafka提供的用来重新分配partition和replica到broker上的工具
简单实现重新分配需要三步：
- 生成分配计划（generate）
- 执行分配（execute）
- 检查分配的状态（verify）
具体操作如下：
1. 生成分配计划
编写分配脚本：
vi topics-to-move.json
内容如下：
{"topics":
[{"topic":"event_request"}],
"version": 1
}
执行分配计划生成脚本：
kafka-reassign-partitions.sh --zookeeper $ZK_CONNECT --topics-to-move-json-file topics-to-move.json --broker-list "5,6,7,8" --generate
执行结果如下：
[hadoop@sdf-nimbus-perf topic_reassgin]$ kafka-reassign-partitions.sh --zookeeper $ZK_CONNECT --topics-to-move-json-file topics-to-move.json --broker-list "5,6,7,8" --generate
Current partition replica assignment #当前分区的副本分配
{"version":1,"partitions":[{"topic":"event_request","partition":0,"replicas":[3,4]},{"topic":"event_request","partition":1,"replicas":[4,5]}]}
Proposed partition reassignment configuration #建议的分区配置
{"version":1,"partitions":[{"topic":"event_request","partition":0,"replicas":[6,5]},{"topic":"event_request","partition":1,"replicas":[7,6]}]}
Proposed partition reassignment configuration 后是根据命令行的指定的brokerlist生成的分区分配计划json格式。将 Proposed partition reassignment configuration的配置copy保存到一个文件中 topic-reassignment.json
vi topic-reassignment.json
{"version":1,"partitions":[{"topic":"event_request","partition":0,"replicas":[6,5]},{"topic":"event_request","partition":1,"replicas":[7,6]}]}
2. 执行分配（execute）
根据step1 生成的分配计划配置json文件topic-reassignment.json，进行topic的重新分配。
kafka-reassign-partitions.sh --zookeeper $ZK_CONNECT --reassignment-json-file topic-reassignment.json --execute
执行前的分区分布：
[hadoop@sdf-nimbus-perf topic_reassgin]$ le-kafka-topics.sh --describe --topic event_request
Topic:event_request PartitionCount:2 ReplicationFactor:2 Configs:
Topic: event_request Partition: 0 Leader: 3 Replicas: 3,4 Isr: 3,4
Topic: event_request Partition: 1 Leader: 4 Replicas: 4,5 Isr: 4,5
执行后的分区分布：
[hadoop@sdf-nimbus-perf topic_reassgin]$ le-kafka-topics.sh --describe --topic event_request
Topic:event_request PartitionCount:2 ReplicationFactor:4 Configs:
Topic: event_request Partition: 0 Leader: 3 Replicas: 6,5,3,4 Isr: 3,4
Topic: event_request Partition: 1 Leader: 4 Replicas: 7,6,4,5 Isr: 4,5
3. 检查分配的状态
查看分配的状态：正在进行
[hadoop@sdf-nimbus-perf topic_reassgin]$ kafka-reassign-partitions.sh --zookeeper $ZK_CONNECT --reassignment-json-file topic-reassignment.json --verify
Status of partition reassignment:
Reassignment of partition [event_request,0] is still in progress
Reassignment of partition [event_request,1] is still in progress
[hadoop@sdf-nimbus-perf topic_reassgin]$
查看“is still in progress” 状态时的分区，副本分布状态：
发现Replicas有4个哦，说明在重新分配的过程中新旧的副本都在进行工作。
[hadoop@sdf-nimbus-perf topic_reassgin]$ le-kafka-topics.sh --describe --topic event_request
Topic:event_request PartitionCount:2 ReplicationFactor:4 Configs:
Topic: event_request Partition: 0 Leader: 3 Replicas: 6,5,3,4 Isr: 3,4
Topic: event_request Partition: 1 Leader: 4 Replicas: 7,6,4,5 Isr: 4,5
查看分配的状态：分配完成。
[hadoop@sdf-nimbus-perf topic_reassgin]$ kafka-reassign-partitions.sh --zookeeper $ZK_CONNECT --reassignment-json-file topic-reassignment.json --verify
Status of partition reassignment:
Reassignment of partition [event_request,0] completed successfully
Reassignment of partition [event_request,1] completed successfully
查看“completed successfully”状态的分区，副本状态：
已经按照生成的分配计划正确的完成了分区的重新分配。
[hadoop@sdf-nimbus-perf topic_reassgin]$ le-kafka-topics.sh --describe --topic event_request
Topic:event_request PartitionCount:2 ReplicationFactor:2 Configs:
Topic: event_request Partition: 0 Leader: 6 Replicas: 6,5 Isr: 6,5
Topic: event_request Partition: 1 Leader: 7 Replicas: 7,6 Isr: 6,7