已创建由三个ZooKeeper服务器组成的ZooKeeper仲裁.
位于所有三个ZooKeeper服务器上的zoo.cfg如下所示：
- maxClientCnxns=50
- # The number of milliseconds of each tick
- tickTime=2000
- # The number of ticks that the initial
- # synchronization phase can take
- initLimit=10
- # The number of ticks that can pass between
- # sending a request and getting an acknowledgement
- syncLimit=5
- # the directory where the snapshot is stored.
- dataDir=/var/lib/zookeeper
- # the port at which the clients will connect
- clientPort=2181
- server.1=<ip-address-1>:2888:3888
- server.2=<ip-address-2>:2888:3888
- server.3=<ip-address-3>:2888:3888
分析
很明显,三个ZooKeeper服务器中的一个将成为领导者和其他粉丝.如果Leader ZooKeeper服务器已关闭,则Leader选举将重新开始.目的是检查Leader服务器是否已关闭,另一个ZooKeeper服务器是否会成为Leader.
题
需要发出什么命令来检查ZooKeeper服务器是领导者还是追随者？
解决方法
可以使用netcat包中包含的nc命令检查ZooKeeper服务器是否是领导者或关注者：
- echo stat | nc localhost 2181 | grep Mode
- echo srvr | nc localhost 2181 | grep Mode #(From 3.3.0 onwards)
如果ZooKeeper服务器是领导者,那么命令将返回：模式：领导者和否则：模式：关注者
