kafka集群扩容后的topic分区迁移

https://www.cnblogs.com/honeybee/p/5691921.html

kafka集群扩容后，新的broker上面不会数据进入这些节点，也就是说，这些节点是空闲的；它只有在创建新的topic时才会参与工作。除非将已有的partition迁移到新的服务器上面；
所以需要将一些topic的分区迁移到新的broker上。

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