本来这一节想写Hadoop的分布式高可用环境的搭建，写到一半，发现还是有必要先介绍一下ZooKeeper这个东西。

ZooKeeper理念介绍

ZooKeeper是为分布式应用来提供协同服务的，而且ZooKeeper本身也是分布式的，由分布在至少三台机器上，这几台机器形成一个Quorum，就想一个剧团一样。这个团里有个团长，就是leader的角色，其他的是follower。这个剧团里的每个人脑子里都记住同样的东西（ZooKeeper是基于内存的），并且及时和leader保持同步，所有client可连接任何一个server即可。剧团里的每个人都有一个编号myid。如果剧团里的leader挂断后，剩下的几个要重新选举出新的leader来确保服务正常运行。

1. ZooKeepe的安装

ZooKeeper的安装挺简单，就是解压，设置环境变量就可以了

[root@hadoop100 bin]# tar -zxvf /opt/software/zookeeper-3.4.10.tar.gz -C /opt/modules/

打开/ect/profile 编辑环境变量，加上下面的内容：

#JAVA_HOME
export JAVA_HOME=/opt/modules/jdk1.8.0_121
export PATH=$PATH:$JAVA_HOME/bin

#HADOOP_HOME
export HADOOP_HOME=/opt/modules/hadoop-2.7.3
export PATH=$PATH:$HADOOP_HOME/bin:$HADOOP_HOME/sbin

#ZOOKEEPER
export ZOOKEEPER_HOME=/opt/modules/zookeeper-3.4.10
export PATH=$PATH:ZOOKEEPER_HOME/bin

然后 source /ect/profile 让更改生效。记得用xsync 和xcall超级脚本，把更改同步到整个集群。

[root@hadoop100 bin]# xsync /etc/profile
[root@hadoop100 bin]# xcall source /etc/profile

2. ZooKeeper的配置

1. Zookeeper 需要一个data目录，用于存储zookeeper内存数据库的镜像和日志。然后更改zoo.cfg文件。ZooKeeper解压后提供了一个/opt/modules/zookeeper-3.4.10/conf/zoo_sample.cfg文件，把这个复制一下或者改个名字叫zoo.cfg, 修改一下里面的dataDir的指向。

# 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=/opt/modules/zookeeper-3.4.10/zkData
# 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
~

要搭建ZooKeeper的机器环境，zookeeper服务器的数量应该是奇数台。最少要3台。

# 连接到leader 服务器的tick数，超过这个tick数 这台服务器还没有连接上leader，那这台机
器就被认为是死掉了
initLimit = 5
# 在和leader同步过程中所允许落后的最大tick数，如果超过这个，那就是掉队了
syncLimit = 2
server.100=hadoop100:2888:3888
server.101=hadoop101:2888:3888
server.102=hadoop102:2888:3888
server.103=hadoop103:2888:3888
server.104=hadoop104:2888:3888

 机器的参数配置的格式是这样的：

注意更改完毕后别忘了分发到集群中。zookeeper本身是也分布式的。先把相关文件分发到集群中的其他机器上。

[root@hadoop100 modules]# xsync zookeeper-3.4.10/

然后为每台机器做上独特的标记，在data目录里创建myId文件，内容就是上面配置文件中的数字

[root@hadoop100 zookeeper-3.4.10]# cd zkData/
[root@hadoop100 zkData]# echo 100 > myid

在集群的其他几台机器上修改myid文件的内容，让myid的内容和配置文件中的编号一致。这时候只能麻烦点，依次登录到每台机器上创建 data目录下的myid文件了。

[root@hadoop100 zkData]# ssh hadoop101

Last login: Thu Sep 19 14:10:35 2019 from gateway
[root@hadoop101 ~]# echo 101 > /opt/modules/zookeeper-3.4.10/zkData/myid
[root@hadoop101 ~]#exit

[root@hadoop100 zkData]# ssh hadoop101
Last login: Thu Sep 19 14:10:35 2019 from gateway
[root@hadoop101 ~]# echo 101 > /opt/modules/zookeeper-3.4.10/zkData/myid
[root@hadoop101 ~]# exit
logout
Connection to hadoop101 closed.
[root@hadoop100 zkData]# ssh hadoop102
Last login: Tue Sep 17 13:26:48 2019 from hadoop100
[root@hadoop102 ~]# echo 102 > /opt/modules/zookeeper-3.4.10/zkData/myid
[root@hadoop102 ~]# exit
logout
Connection to hadoop102 closed.
[roo 3ff8 t@hadoop100 zkData]# ssh hadoop103
Last login: Tue Sep 17 13:17:00 2019 from hadoop100
[root@hadoop103 ~]# echo 103 > /opt/modules/zookeeper-3.4.10/zkData/myid
[root@hadoop103 ~]# exit
logout
Connection to hadoop103 closed.
[root@hadoop100 zkData]# ssh hadoop104
Last login: Tue Sep 17 11:04:38 2019 from hadoop100
[root@hadoop104 ~]# echo 104 > /opt/modules/zookeeper-3.4.10/zkData/myid
[root@hadoop104 ~]# exit
logout
Connection to hadoop104 closed.

检查一下确保没问题

[root@hadoop100 bin]# xcall cat /opt/modules/zookeeper-3.4.10/zkData/myid
---------running at localhost--------
100
---------running at hadoop101-------
101
---------running at hadoop102-------
102
---------running at hadoop103-------
103
---------running at hadoop104-------
104
[root@hadoop100 bin]#

好了，基本配置好了，准备启动了，ZooKeeper集群都要启动ZooKeeper服务。我用之前介绍过的超级脚本xcall

[root@hadoop100 zkData]# xcall /opt/modules/zookeeper-3.4.10/bin/zkServer.sh start
---------running at localhost--------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
---------running at hadoop101-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
---------running at hadoop102-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
---------running at hadoop103-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
---------running at hadoop104-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[root@hadoop100 zkData]#

错误排查：Error contacting service. It is probably not running.

查看一下运行状态, 啊哦，怎么没启动呢？ 

[root@hadoop100 bin]# xcall /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
---------running at localhost--------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
---------running at hadoop101-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
---------running at hadoop102-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
---------running at hadoop103-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
---------running at hadoop104-------
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Error contacting service. It is probably not running.
[root@hadoop100 bin]#

后来发现需要单独ssh到每台机器上单独启动就可以了，可能是xcall神器有的时候不可靠。不过提示一点，zkServer.sh start-foreground 命令，可以在查看详细启动过程，方便排查错误。

[root@hadoop101 ~]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh start-foreground
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
2019-09-19 14:52:29,093 [myid:] - INFO  [main:QuorumPeerConfig@134] - Reading configuration from: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
2019-09-19 14:52:29,122 [myid:] - INFO  [main:QuorumPeer$QuorumServer@167] - Resolved hostname: hadoop104 to address: hadoop104/192.168.56.104
2019-09-19 14:52:29,123 [myid:] - INFO  [main:QuorumPeer$QuorumServer@167] - Resolved hostname: hadoop103 to address: hadoop103/192.168.56.103
2019-09-19 14:52:29,123 [myid:] - INFO  [main:QuorumPeer$QuorumServer@167] - Resolved hostname: hadoop102 to address: hadoop102/192.168.56.102
2019-09-19 14:52:29,124 [myid:] - INFO  [main:QuorumPeer$QuorumServer@167] - Resolved hostname: hadoop101 to address: hadoop101/192.168.56.101
2019-09-19 14:52:29,124 [myid:] - INFO  [main:QuorumPeer$QuorumServer@167] - Resolved hostname: hadoop100 to address: hadoop100/192.168.56.100
2019-09-19 14:52:29,124 [myid:] - INFO  [main:QuorumPeerConfig@396] - Defaulting to majority quorums
2019-09-19 14:52:29,134 [myid:101] - INFO  [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3
2019-09-19 14:52:29,135 [myid:101] - INFO  [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 0
2019-09-19 14:52:29,135 [myid:101] - INFO  [main:DatadirCleanupManager@101] - Purge task is not scheduled.
2019-09-19 14:52:29,150 [myid:101] - INFO  [main:QuorumPeerMain@127] - Starting quorum peer
2019-09-19 14:52:29,171 [myid:101] - INFO  [main:NIOServerCnxnFactory@89] - binding to port 0.0.0.0/0.0.0.0:2181
2019-09-19 14:52:29,172 [myid:101] - ERROR [main:QuorumPeerMain@89] - Unexpected exception, exiting abnormally
java.net.BindException: Address already in use
at sun.nio.ch.Net.bind0(Native Method)
at sun.nio.ch.Net.bind(Net.java:433)
at sun.nio.ch.Net.bind(Net.java:425)
at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:223)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:74)
at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:67)
at org.apache.zookeeper.server.NIOServerCnxnFactory.configure(NIOServerCnxnFactory.java:90)
at org.apache.zookeeper.server.quorum.QuorumPeerMain.runFromConfig(QuorumPeerMain.java:130)
at org.apache.zookeeper.server.quorum.QuorumPeerMain.initializeAndRun(QuorumPeerMain.java:111)
at org.apache.zookeeper.server.quorum.QuorumPeerMain.main(QuorumPeerMain.java:78)
[root@hadoop101 ~]#

如果jps命令能看到QuorumPeerMain就是已经启动成功了。

[root@hadoop100 bin]# jps
1885 QuorumPeerMain
2029 Jps

SSH单独登录到各个服务器上依次启动，并查看状态，可以发现我现在的集群环境中hadoop102是leader，其他几台是follower：

[root@hadoop100 bin]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
[root@hadoop100 bin]# ssh hadoop101
Last login: Thu Sep 19 15:04:12 2019 from hadoop100
[root@hadoop101 ~]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
[root@hadoop101 ~]# exit
logout
Connection to hadoop101 closed.
[root@hadoop100 bin]# ssh hadoop102
Last login: Thu Sep 19 15:04:48 2019 from hadoop100
[root@hadoop102 ~]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: leader
[root@hadoop102 ~]# exit
logout
Connection to hadoop102 closed.
[root@hadoop100 bin]# ssh hadoop103
Last login: Thu Sep 19 15:05:07 2019 from hadoop100
[root@hadoop103 ~]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
[root@hadoop103 ~]# exit
logout
Connection to hadoop103 closed.
[root@hadoop100 bin]# ssh hadoop104
Last login: Thu Sep 19 15:05:51 2019 from hadoop100
[root@hadoop104 ~]# /opt/modules/zookeeper-3.4.10/bin/zkServer.sh status
ZooKeeper JMX enabled by default
Using config: /opt/modules/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
[root@hadoop104 ~]# exit
logout
Connection to hadoop104 closed.
[root@hadoop100 bin]#

好了，到现在为止，我的ZooKeeper集群环境已经搭建成功了。 

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