[大数据学习研究] 4. Zookeeper-分布式服务的协同管理神器
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，就像一个剧团一样。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，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：
server.a=b:c:d。
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是这个服务器与集群中的leader服务器交换信息的端口；
d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。
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.
[root@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. (后来发现用这种方式靠不住，说是启动了，其实没启动 ;;;)
[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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