分布式架构学习之：027--ZooKeeper集群的安装、配置、高可用测试
Dubbo 建议使用 Zookeeper 作为服务的注册中心
Zookeeper 集群中只要有过半的节点是正常的情况下，那么整个集群对外就是可用的。正是基于这个 特性，要将 ZK 集群的节点数量要为奇数（2n+1：如 3、5、7 个节点）较为合适。
ZooKeeper 与 Dubbo 服务集群架构图
服务器 1：192.168.1.81 端口：2181、2881、3881
服务器 2：192.168.1.82 端口：2182、2882、3882
服务器 3：192.168.1.83 端口：2183、2883、3883
一、集群节点安装和配置
1、 修改操作系统的/etc/hosts 文件，添加 IP 与主机名映射：
# zookeeper cluster servers 192.168.1.81 edu-zk-01 192.168.1.82 edu-zk-02 192.168.1.83 edu-zk-03
2、 下载或上传 zookeeper-3.4.6.tar.gz 到/home/wusc/zookeeper 目录：
$ cd /home/wusc/zookeeper
$ wget http://apache.fayea.com/zookeeper/zookeeper-3.4.6/zookeeper-3.4.6.tar.gz
3、 解压 zookeeper 安装包，并按节点号对 zookeeper 目录重命名：
$ tar -zxvf zookeeper-3.4.6.tar.gz
服务器 1：
$ mv zookeeper-3.4.6 node-01
服务器 2：
$ mv zookeeper-3.4.6 node-02
服务器 3：
$ mv zookeeper-3.4.6 node-03
4、 在各 zookeeper 节点目录下创建以下目录：
$ cd /home/wusc/zookeeper/node-0X(X 代表节点号 1、2、3，以下同解)
$ mkdir data
$ mkdir logs
5、 将 zookeeper/node-0X/conf 目录下的 zoo_sample.cfg 文件拷贝一份，命名为 zoo.cfg:
$ cp zoo_sample.cfg zoo.cfg
6、 修改 zoo.cfg 配置文件：
zookeeper/node-01 的配置（/home/wusc/zookeeper/node-01/conf/zoo.cfg）如下：
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/wusc/zookeeper/node-01/data
dataLogDir=/home/wusc/zookeeper/node-01/logs
clientPort=2181
server.1=edu-zk-01:2881:3881
server.2=edu-zk-02:2882:3882
server.3=edu-zk-03:2883:3883
zookeeper/node-02 的配置（/home/wusc/zookeeper/node-02/conf/zoo.cfg）如下：
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/wusc/zookeeper/node-02/data
dataLogDir=/home/wusc/zookeeper/node-02/logs
clientPort=2182
server.1=edu-zk-01:2881:3881
server.2=edu-zk-02:2882:3882
server.3=edu-zk-03:2883:3883
zookeeper/node-03 的配置（/home/wusc/zookeeper/node-03/conf/zoo.cfg）如下：
tickTime=2000
initLimit=10
syncLimit=5
dataDir=/home/wusc/zookeeper/node-03/data
dataLogDir=/home/wusc/zookeeper/node-03/logs
clientPort=2183
server.1=edu-zk-01:2881:3881
server.2=edu-zk-02:2882:3882
server.3=edu-zk-03:2883:3883
参数说明:
tickTime=2000tickTime 这个时间是作为 Zookeeper 服务器之间或客户端与服务器之间维持心跳的时间间隔,也就是每个 tickTime 时间就会发送一个心跳。
initLimit=10initLimit 这个配置项是用来配置 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=5syncLimit 这个配置项标识 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。
dataDir=/home/wusc/zookeeper/node-01/data
dataDir 顾名思义就是 Zookeeper 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=2181
clientPort 这个端口就是客户端（应用程序）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
server.1=edu-zk-01:2881:3881
server.2=edu-zk-02:2882:3882
server.3=edu-zk-03:2883:3883
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（或者是与 IP 地址做了映射的主机名）；
C 第一个端口用来集群成员的信息交换,表示这个服务器与集群中的 Leader 服务器交换信息的端口；
D 是在 leader 挂掉时专门用来进行选举 leader 所用的端口。
注意：如果是伪集群的配置方式，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。
7、在 dataDir=/home/wusc/zookeeper/node-0X/data下创建 myid文件
编辑 myid 文件，并在对应的IP 的机器上输入对应的编号。如在node-01 上，myid 文件内容就是1,node-02 上就是 2，node-03 上就是 3：
|
$ |
vi /home/wusc/zookeeper/node-01/data/myid |
## 值为 1 |
||
|
$ |
vi |
/home/wusc/zookeeper/node-02/data/myid |
## |
值为 2 |
|
$ |
vi |
/home/wusc/zookeeper/node-03/data/myid |
## |
值为 3 |
8、 在防火墙中打开要用到的端口 218X、288X、388X
切换到 root 用户权限，执行以下命令：
# chkconfig iptables on
# service iptables start
编辑/etc/sysconfig/iptables
# vi /etc/sysconfig/iptables
如服务器 01 增加以下 3 行：
## zookeeper
-A INPUT -m state --state NEW -m tcp -p tcp --dport 2181 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 2881 -j ACCEPT
-A INPUT -m state --state NEW -m tcp -p tcp --dport 3881 -j ACCEPT
重启防火墙：
# service iptables restart
查看防火墙端口状态：
# service iptables status
9、 启动并测试 zookeeper（要用 wusc 用户启动，不要用 root）:
(1) 使用 wusc 用户到/home/wusc/zookeeper/node-0X/bin 目录中执行：
$ /home/wusc/zookeeper/node-01/bin/zkServer.sh start
$ /home/wusc/zookeeper/node-02/bin/zkServer.sh start
$ /home/wusc/zookeeper/node-03/bin/zkServer.sh start
(2) 输入jps 命令查看进程：
$ jps
1456
QuorumPeerMain
其中，QuorumPeerMain 是zookeeper 进程，说明启动正常
(3) 查看状态：
$ /home/wusc/zookeeper/node-01/bin/zkServer.sh status
(4) 查看 zookeeper 服务输出信息：
由于服务信息输出文件在/home/wusc/zookeeper/node-0X/bin/zookeeper.out
$ tail -500f zookeeper.out
10、停止 zookeeper 进程：
$ zkServer.sh stop
11、配置 zookeeper 开机使用 wusc 用户启动：
编辑 node-01、node-02、node-03 中的/etc/rc.local 文件，分别加入：
su - wusc -c '/home/wusc/zookeeper/node-01/bin/zkServer.sh start'
su - wusc -c '/home/wusc/zookeeper/node-02/bin/zkServer.sh start'
su - wusc -c '/home/wusc/zookeeper/node-03/bin/zkServer.sh start'
二、安装 Dubbo 管控台（主要是配置连接集群）：
Dubbo 管控台可以对注册到 zookeeper 注册中心的服务或服务消费者进行管理，但管控台是否正常对Dubbo 服务没有影响，管控台也不需要高可用，因此可以单节点部署。
IP: 192.168.1.81
部署容器：Tomcat7
端口：8080
1、 下载（或上传）最新版的 Tomcat7（apache-tomcat-7.0.57.tar.gz）到/home/wusc/
2、 解压：
$ tar -zxvf apache-tomcat-7.0.57.tar.gz
$ mv apache-tomcat-7.0.57 dubbo-admin-tomcat
3、 移除/home/wusc/dubbo-admin-tomcat/webapps 目录下的所有文件：
$ rm -rf *
4、 上传 Dubbo 管理控制台程序 dubbo-admin-2.5.3.war到/home/wusc/dubbo-admin-tomcat/webapps
5、 解压并把目录命名为 ROOT:
$ unzip dubbo-admin-2.5.3.war -d ROOT
把 dubbo-admin-2.5.3.war 移到/home/wusc/tools 目录备份
$ mv dubbo-admin-2.5.3.war /home/wusc/tools
6、 配置 dubbo.properties：
[[email protected] WEB-INF]# vi dubbo.properties[[email protected] WEB-INF]# cat dubbo.properties | grep re
dubbo.registry.address=zookeeper://192.168.1.81:2181?backup=192.168.1.82:2182,192.168.1.83:2183
三、测试集群高可用
启用edu-zk-03,这里是从节点
[[email protected] conf]# /home/wusc/zookeeper/node-03/bin/zkServer.sh start
JMX enabled by default
Using config: /home/wusc/zookeeper/node-03/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED
[[email protected] conf]# /home/wusc/zookeeper/node-03/bin/zkServer.sh status
JMX enabled by default
Using config: /home/wusc/zookeeper/node-03/bin/../conf/zoo.cfg
Mode: follower
我们再关掉edu-zk-02的leader节点
[[email protected] root]# /home/wusc/zookeeper/node-02/bin/zkServer.sh stop
JMX enabled by default
Using config: /home/wusc/zookeeper/node-02/bin/../conf/zoo.cfg
Stopping zookeeper ... STOPPED
我们再查看edu-zk-03 status
[[email protected] conf]# /home/wusc/zookeeper/node-03/bin/zkServer.sh status
JMX enabled by default
Using config: /home/wusc/zookeeper/node-03/bin/../conf/zoo.cfg
Mode: leader
这时edu-zk-03变成了leader,
provider控制台信息
016-04-15 16:53:15,516 WARN [ClientCnxn.java:1089] : Session 0x15418fd25210000 for server null, unexpected error, closing socket connection and attempting reconnect
java.net.ConnectException: Connection refused: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:735)
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:350)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
2016-04-15 16:53:15,517 DEBUG [ClientCnxnSocketNIO.java:192] : Ignoring exception during shutdown input
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:798)
at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:426)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:189)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:53:15,518 DEBUG [ClientCnxnSocketNIO.java:199] : Ignoring exception during shutdown output
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:815)
at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:434)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:196)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:53:16,506 INFO [ClientCnxn.java:966] : Opening socket connection to server 192.168.1.83/192.168.1.83:2183. Will not attempt to authenticate using SASL (unknown error)
2016-04-15 16:53:16,507 INFO [ClientCnxn.java:849] : Socket connection established to 192.168.1.83/192.168.1.83:2183, initiating session
2016-04-15 16:53:16,510 DEBUG [ClientCnxn.java:889] : Session establishment request sent on 192.168.1.83/192.168.1.83:2183
2016-04-15 16:53:16,515 INFO [ClientCnxn.java:1207] : Session establishment complete on server 192.168.1.83/192.168.1.83:2183, sessionid = 0x15418fd25210000, negotiated timeout = 30000
2016-04-15 16:53:16,515 DEBUG [ZkClient.java:351] : Received event: WatchedEvent state:SyncConnected type:None path:null
2016-04-15 16:53:16,516 INFO [ZkClient.java:449] : zookeeper state changed (SyncConnected)
2016-04-15 16:53:16,516 DEBUG [ZkEventThread.java:88] : New event: ZkEvent[State changed to SyncConnected sent to com.alib[email protected]20f8f517]
2016-04-15 16:53:16,516 DEBUG [ZkClient.java:395] : Leaving process event
2016-04-15 16:53:16,516 DEBUG [ZkEventThread.java:69] : Delivering event #2 ZkEvent[State changed to SyncConnected sent to com.alib[email protected]20f8f517]
2016-04-15 16:53:16,517 DEBUG [ZkEventThread.java:79] : Delivering event #2 done
JMX enabled by default
Using config: /home/yxq/zookeeper/node-03/bin/../conf/zoo.cfg
Mode: leader
我们再关闭edu-zk-01节点
这里provider控制台信息报错(集群节点没有过半),这时dubbo管理台是可以正常运行的，但是集群是无用，提供者服务是缓存的，如果重启dubbo管理控制台，会发现启动不了，但是如果再启动一个节点edu-zk-01或edu-zk-02,管理控制台又立即可以运行起来。
java.net.SocketException: Connection reset by peer: shutdown
at sun.nio.ch.Net.shutdown(Native Method)
at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:819)
at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:434)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:196)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:58:09,848 INFO [ClientCnxn.java:966] : Opening socket connection to server 192.168.1.81/192.168.1.81:2181. Will not attempt to authenticate using SASL (unknown error)
2016-04-15 16:58:10,848 WARN [ClientCnxn.java:1089] : Session 0x15418fd25210000 for server null, unexpected error, closing socket connection and attempting reconnect
java.net.ConnectException: Connection refused: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:735)
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:350)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
2016-04-15 16:58:10,848 DEBUG [ClientCnxnSocketNIO.java:192] : Ignoring exception during shutdown input
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:798)
at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:426)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:189)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:58:10,849 DEBUG [ClientCnxnSocketNIO.java:199] : Ignoring exception during shutdown output
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:815)
at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:434)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:196)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:58:11,552 INFO [ClientCnxn.java:966] : Opening socket connection to server 192.168.1.82/192.168.1.82:2182. Will not attempt to authenticate using SASL (unknown error)
2016-04-15 16:58:12,553 WARN [ClientCnxn.java:1089] : Session 0x15418fd25210000 for server null, unexpected error, closing socket connection and attempting reconnect
java.net.ConnectException: Connection refused: no further information
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:735)
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:350)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1068)
2016-04-15 16:58:12,554 DEBUG [ClientCnxnSocketNIO.java:192] : Ignoring exception during shutdown input
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownInput(SocketChannelImpl.java:798)
at sun.nio.ch.SocketAdaptor.shutdownInput(SocketAdaptor.java:426)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:189)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:58:12,555 DEBUG [ClientCnxnSocketNIO.java:199] : Ignoring exception during shutdown output
java.nio.channels.ClosedChannelException
at sun.nio.ch.SocketChannelImpl.shutdownOutput(SocketChannelImpl.java:815)
at sun.nio.ch.SocketAdaptor.shutdownOutput(SocketAdaptor.java:434)
at org.apache.zookeeper.ClientCnxnSocketNIO.cleanup(ClientCnxnSocketNIO.java:196)
at org.apache.zookeeper.ClientCnxn$SendThread.cleanup(ClientCnxn.java:1157)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1097)
2016-04-15 16:58:13,909 INFO [ClientCnxn.java:966] : Opening socket connection to server 192.168.1.83/192.168.1.83:2183. Will not attempt to authenticate using SASL (unknown error)
2016-04-15 16:58:13,910 INFO [ClientCnxn.java:849] : Socket connection established to 192.168.1.83/192.168.1.83:2183, initiating session
2016-04-15 16:58:13,911 DEBUG [ClientCnxn.java:889] : Session establishment request sent on 192.168.1.83/192.168.1.83:2183
2016-04-15 16:58:13,914 INFO [ClientCnxn.java:1085] : Unable to read additional data from server sessionid 0x15418fd25210000, likely server has closed socket, closing socket connection and attempting reconnect
2016-04-15 16:58:13,915 DEBUG [ClientCnxnSocketNIO.java:199] : Ignoring exception during shutdown output
四、注册中心的升级或者迁移