zookeeper，是一个分布式服务框架，是Apache Hadoop 的一个子项目，它主要是用来解决分布式应用中经常遇到的一些数据管理问题，如：统一命名服务、状态同步服务、集群管理、分布式应用配置项的管理等。
每个子目录项如 NameService 都被称作为 znode(目录节点)，和文件系统一样，我们能够自由的增加、删除znode，在一个znode下增加、删除子znode，唯一的不同在于znode是可以存储数据的。
有四种类型的znode：
PERSISTENT-持久化目录节点客户端与zookeeper断开连接后，该节点依旧存在
PERSISTENT_SEQUENTIAL-持久化顺序编号目录节点客户端与zookeeper断开连接后，该节点依旧存在，只是Zookeeper给该节点名称进行顺序编号
EPHEMERAL-临时目录节点客户端与zookeeper断开连接后，该节点被删除
EPHEMERAL_SEQUENTIAL-临时顺序编号目录节点客户端与zookeeper断开连接后，该节点被删除，只是Zookeeper给该节点名称进行顺序编号
下载地址
https://downloads.apache.org/zookeeper/zookeeper-3.5.8/ wget https://downloads.apache.org/zookeeper/zookeeper-3.5.8/apache-zookeeper-3.5.8-bin.tar.gzcfg.zoo配置
# 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. # do not use /tmp for storage, /tmp here is just # example sakes. dataDir=/home/hadoop/soft/zookeeper # the port at which the clients will connect clientPort=2181 # the maximum number of client connections. # increase this if you need to handle more clients #maxClientCnxns=60 # # Be sure to read the maintenance section of the # administrator guide before turning on autopurge. # # http://zookeeper.apache.org/doc/current/zookeeperAdmin.html#sc_maintenance # # The number of snapshots to retain in dataDir #autopurge.snapRetainCount=3 # Purge task interval in hours # Set to "0" to disable auto purge feature #autopurge.purgeInterval=1 server.1=192.168.153.131:28888:3888 server.2=192.168.153.134:28888:3888 server.3=192.168.153.135:28888:3888配置参数说明
参数参数说明tickTimeZookeeper 服务器之间或客户端与服务器之间维持心跳的时间间隔，每个 tickTime 时间就会发送一个心跳initLimit配置 Zookeeper 接受客户端（这里所说的客户端不是用户连接 Zookeeper 服务器的客户端，而是 Zookeeper 服务器集群中连接到 Leader 的 Follower 服务器）初始化连接时最长能忍受多少个心跳时间间隔数，当已经超过 10个心跳的时间（也就是 tickTime）长度后 Zookeeper 服务器还没有收到客户端的返回信息，那么表明这个客户端连接失败。总的时间长度就是 10*2000=20 秒syncLimit标识 Leader 与 Follower 之间发送消息，请求和应答时间长度，最长不能超过多少个 tickTime 的时间长度，总的时间长度就是 5*2000=10秒dataDirZookeeper 保存数据的目录，默认情况下，Zookeeper 将写数据的日志文件也保存在这个目录里clientPort客户端连接 Zookeeper 服务器的端口，Zookeeper 会监听这个端口，接受客户端的访问请求server.A=B：C：D其中 A 是一个数字，表示这个是第几号服务器；B 是这个服务器的 ip 地址；C 表示的是这个服务器与集群中的 Leader 服务器交换信息的端口；D 表示的是万一集群中的 Leader 服务器挂了，需要一个端口来重新进行选举，选出一个新的 Leader，而这个端口就是用来执行选举时服务器相互通信的端口。如果是伪集群的配置方式，由于 B 都是一样，所以不同的 Zookeeper 实例通信端口号不能一样，所以要给它们分配不同的端口号标识Server ID
[hadoop@master conf]$ mkdir /home/hadoop/soft/zookeeper [hadoop@master conf]$ cd /home/hadoop/soft/zookeeper [hadoop@master zookeeper]$ echo 1 >myid [hadoop@master zookeeper]$ cat myid 1复制zookeeper文件到其他服务器
scp -r /home/hadoop/soft/apache-zookeeper-3.5.8 slave1:/home/hadoop/soft scp -r /home/hadoop/soft/apache-zookeeper-3.5.8 slave2:/home/hadoop/soft修改其他服务器的Server ID
[hadoop@slave1 ~]$ mkdir /home/hadoop/soft/zookeeper [hadoop@slave1 ~]$ echo 2 >myid [hadoop@slave1 ~]$ cat myid [hadoop@slave2 ~]$ mkdir /home/hadoop/soft/zookeeper [hadoop@slave2 ~]$ echo 3 >myid启动
[hadoop@master apache-zookeeper-3.5.8]$ ./bin/zkServer.sh start ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Starting zookeeper ... STARTED [hadoop@master apache-zookeeper-3.5.8]$ pwd /home/hadoop/soft/apache-zookeeper-3.5.8 [hadoop@master apache-zookeeper-3.5.8]$ ./bin/zkServer.sh status ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Client port found: 2181. Client address: localhost. Mode: follower [hadoop@slave2 apache-zookeeper-3.5.8]$ ./bin/zkServer.sh start ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Starting zookeeper ... STARTED [hadoop@slave2 apache-zookeeper-3.5.8]$ ./bin/zkServer.sh status ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Client port found: 2181. Client address: localhost. Mode: leader [hadoop@slave1 apache-zookeeper-3.5.8]$ ./bin/zkServer.sh start ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Starting zookeeper ... STARTED [hadoop@slave1 apache-zookeeper-3.5.8]$ ./bin/zkServer.sh status ZooKeeper JMX enabled by default Using config: /home/hadoop/soft/apache-zookeeper-3.5.8/bin/../conf/zoo.cfg Client port found: 2181. Client address: localhost. Mode: follower查看进程
[hadoop@slave1 apache-zookeeper-3.5.8]$ jps 1700 QuorumPeerMain 1782 ZooKeeperMain 1885 Jps [hadoop@slave2 apache-zookeeper-3.5.8]$ jps 1562 Jps 1374 QuorumPeerMain [hadoop@master apache-zookeeper-3.5.8]$ jps 1586 QuorumPeerMain 1764 Jps查看zookeeper目录
[hadoop@slave1 apache-zookeeper-3.5.8]$ ./bin/zkCli.sh [zk: localhost:2181(CONNECTED) 0] ls / [zookeeper] [zk: localhost:2181(CONNECTED) 1] create /zmw Created /zmw [zk: localhost:2181(CONNECTED) 2] ls / [zmw, zookeeper] [zk: localhost:2181(CONNECTED) 3] create /test testData Created /test [zk: localhost:2181(CONNECTED) 4] ls / [test, zmw, zookeeper] [zk: localhost:2181(CONNECTED) 5] get /test testData
