最近我们生产环境的kafka集群有增加节点的需求,然而kafka在新增节点后并不会像elasticsearch那样感知到新节点加入后自动将数据reblance到新集群中,因此这个过程需要我们手动分配。一番折腾之后,实现了增加kafka集群节点并将原有数据均匀分配到扩容后的集群。下面结合一个例子谈一下整个过程。
一、环境说明
1.集群状况
假定当前的cluster中只有(101,102,103)三个kafka节点,有一个名为think_tank的topic,该topic有2个replica,均匀分布在三个节点上.
2.目的
我们要做的是在cluster中新增两个节点(记为104,105)后,将的数据均匀分到新集群中的5个节点上。
二、操作步骤
新增kafka节点的部署不是本文重点,就不在此赘述。
其实官方文档的这一小节关于集群扩容讲解很详细:Expanding your cluster ,整个过程需要分为三个步骤:获取kafka给出的建议分配方案、按照给出的分配方案执行分配、查看分配的进度以及状态。这三个步骤对应了kafka脚本提供的三个partition reassigment工具。
--generate: In this mode, given a list of topics and a list of brokers, the tool generates a candidate reassignment to move all partitions of the specified topics to the new brokers. This option merely provides a convenient way to generate a partition reassignment plan given a list of topics and target brokers.
--execute: In this mode, the tool kicks off the reassignment of partitions based on the user provided reassignment plan. (using the --reassignment-json-file option). This can either be a custom reassignment plan hand crafted by the admin or provided by using the --generate option
--verify: In this mode, the tool verifies the status of the reassignment for all partitions listed during the last --execute. The status can be either of successfully completed, failed or in progress
结合例子具体说明:
1、生成重新分配topic的方案
脚本的参数是以json文件的形式传入的,首先要新建一个json文件并设置需要分配哪些topic,think_tank-to-move.json:
{
"topics":[
{
"topic":"think_tank"
},
{
"topic":"这里可以同时指定多个..."
}
],
"version":1
}
使用/bin目录中提供的kafka-reassign-partitions.sh
的脚本请求获取生成分配方案:
./bin/kafka-reassign-partitions.sh --zookeeper your_zk_address:2181 --topics-to-move-json-file think_tank-to-move.json --broker-list "101,102,103,104,105" --generate
--broker-lsit 的参数 "101,102,103,104,105"是指集群中每个broker的id,由于我们是需要将所有topic均匀分配到扩完结点的5台机器上,所以要指定。同理,当业务改变为将原来的所有数据从旧节点(01,102,103)迁移到新节点(104,105)实现数据平滑迁移,这时的参数应"104,105".
脚本执行后返回的结果如下:
Current partition replica assignment
{"version":1,"partitions":[{"topic":"think_tank","partition":2,"replicas":[101,102]},{"topic":"think_tank","partition":4,"replicas":[103,102]},{"topic":"think_tank","partition":3,"replicas":[102,101]},{"topic":"think_tank","partition":0,"replicas":[102,103]},{"topic":"think_tank","partition":1,"replicas":[103,101]}]}
Proposed partition reassignment configuration
{"version":1,"partitions":[{"topic":"think_tank","partition":2,"replicas":[103,101]},{"topic":"think_tank","partition":4,"replicas":[105,103]},{"topic":"think_tank","partition":3,"replicas":[104,102]},{"topic":"think_tank","partition":0,"replicas":[101,104]},{"topic":"think_tank","partition":1,"replicas":[102,105]}]}
可以看出当前正在运行的方案中,think_tank的replica都是分布在101,102,103这3个节点,新给出的建议方案中replica均匀分布在扩容后的5个节点中。
2.执行分配方案
将上一个步骤中生成的建议方案复制到新建的think_tank_reassignment.json中:
{"version":1,"partitions":[{"topic":"think_tank","partition":2,"replicas":[103,101]},{"topic":"think_tank","partition":4,"replicas":[105,103]},{"topic":"think_tank","partition":3,"replicas":[104,102]},{"topic":"think_tank","partition":0,"replicas":[101,104]},{"topic":"think_tank","partition":1,"replicas":[102,105]}]}
使用脚本执行:
./bin/kafka-reassign-partitions.sh --zookeeper your_zk_address:2181 --reassignment-json-file think_tank_reassignment.json --execute
脚本执行,返回内容:
Current partition replica assignment
{"version":1,"partitions":[{"topic":"think_tank","partition":2,"replicas":[101,102]},{"topic":"think_tank","partition":4,"replicas":[103,102]},{"topic":"think_tank","partition":3,"replicas":[102,101]},{"topic":"think_tank","partition":0,"replicas":[102,103]},{"topic":"think_tank","partition":1,"replicas":[103,101]}]}
Save this to use as the --reassignment-json-file option during rollback
Successfully started reassignment of partitions.
如上,成功开始执行分配数据,同时提示你如果有需要将之前的分配方案备份便于回滚到原方案。
3.查看配过程进
查看脚本的方法如下,注意这次的json文件要和执行步骤中的json是同一个文件:
./bin/kafka-reassign-partitions.sh --zookeeper your_zk_address:2181 --reassignment-json-file think_tank_reassignment.json --verify
返回结果:
Reassignment of partition [think_tank,2] completed successfully
Reassignment of partition [think_tank,1] completed successfully
Reassignment of partition [think_tank,3] is still in progress
Reassignment of partition [think_tank,4] completed successfully
Reassignment of partition [think_tank,0] is still in progress
is still in progress表示还在处理中,全部迁移成功后每个partition都会显示 completed successfully.注意如果topic数据量大,这个过程可能会时间长一些,不要轻易重启节点!
可能会导致数据不一致!!!
三、其它
这个partion reassignment工具同样可以按需手动地将某个特定的topic指定到特定的broker上,所要做的就是按照步骤一给定的格式关联partition到borker即可,如,将think_tank的partition0指定到101、102两节点上:
{
"version":1,
"partitions":[
{
"topic":"think_tank",
"partition":0,
"replicas":[
101,
105
]
}
]
}
另外,如果有增加replica的个数的需求,同样可以使用这个脚本,可以翻一下官网文档。
One more thing
一点儿感触,在确定问题所在后,官方的文档应该作为我们优先考虑的一个重要资料源,网上的资料由于时间较早、版本不同的原因,解决方式可能需要细微的改动才能达到目的,这些坑在官方的一手资料上其实是可以规避的。
来源:oschina
链接:https://my.oschina.net/xiaominmin/blog/4286113