zookeeper正常，kafka总是挂掉的问题：A broker is already registered on the path /brokers/ids/0.

打开zookeeper集群之后，zk正常，但是kafka启动之后总是会挂掉，查找logs日志里的server.log文件发现问题：

问题：A broker is already registered on the path /brokers/ids/0. This probably indicates that you either have configured a brokerid that is already in use, or else you have shutdown this broker and restarted it faster than the zookeeper timeout so it appears to be re-registering.

这可能是之前机器因为卡死或物理重启，kafka broker没有正常下线，zk上还保留着它的broker id。所以直接删除zk上的brokerid就可以了。

具体解决步骤如下：

1、进入zookeeper的客户端

[admin@hadoop102 zookeeper-3.4.10]$ bin/zkCli.sh

2、进入客户端以后查看注册信息

[zk: localhost:2181(CONNECTED) 2] ls /

 3、进入brokers查看ids的信息

[zk: localhost:2181(CONNECTED) 10] ls /brokers/ids

4、删除这些注册信息就ok

[zk: localhost:2181(CONNECTED) 11] delete /brokers/ids

 

5、在开启kafka，就没问题了。