四、Zookeeper实战

4.1 分布式安装部署

1．集群规划
在hadoop102、hadoop103和hadoop104三个节点上部署Zookeeper。
2．解压安装
（1）解压Zookeeper安装包到/opt/module/目录下
$ tar -zxvf zookeeper-3.4.10.tar.gz -C /opt/module/
（2）同步/opt/module/zookeeper-3.4.10目录内容到hadoop103、hadoop104
$ xsync zookeeper-3.4.10/
3．配置服务器编号
（1）在/opt/module/zookeeper-3.4.10/这个目录下创建zkData
$ mkdir -p zkData
（2）在/opt/module/zookeeper-3.4.10/zkData目录下创建一个myid的文件
$ touch myid
添加myid文件，注意一定要在linux里面创建，在notepad++里面很可能乱码
（3）编辑myid文件
$ vi myid
    在文件中添加与server对应的编号：2
（4）拷贝配置好的zookeeper到其他机器上
$ xsync myid
并分别在hadoop102、hadoop103上修改myid文件中内容为3、4
4．配置zoo.cfg文件
（1）重命名/opt/module/zookeeper-3.4.10/conf这个目录下的zoo_sample.cfg为zoo.cfg
$ mv zoo_sample.cfg zoo.cfg
（2）打开zoo.cfg文件
$ vim zoo.cfg
修改数据存储路径配置
dataDir=/opt/module/zookeeper-3.4.10/zkData
增加如下配置
#######################cluster##########################
server.2=hadoop102:2888:3888
server.3=hadoop103:2888:3888
server.4=hadoop104:2888:3888
（3）同步zoo.cfg配置文件
$ xsync zoo.cfg
（4）配置参数解读
server.A=B:C:D。
A是一个数字，表示这个是第几号服务器；
集群模式下配置一个文件myid，这个文件在dataDir目录下，这个文件里面有一个数据就是A的值，Zookeeper启动时读取此文件，拿到里面的数据与zoo.cfg里面的配置信息比较从而判断到底是哪个server。
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。
4．集群操作
（1）分别启动Zookeeper
$ bin/zkServer.sh start
（2）查看状态
bin/zkServer.sh status
JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower
bin/zkServer.sh status
JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: leader
bin/zkServer.sh status
JMX enabled by default
Using config: /opt/module/zookeeper-3.4.10/bin/../conf/zoo.cfg
Mode: follower

4.2 客户端命令行操作

命令基本语法	功能描述
help	显示所有操作命令
ls path [watch]	使用 ls 命令来查看当前znode中所包含的内容
ls2 path [watch]	查看当前节点数据并能看到更新次数等数据
create	普通创建 -s 含有序列 -e 临时（重启或者超时消失）
get path [watch]	获得节点的值
set	设置节点的具体值
stat	查看节点状态
delete	删除节点
rmr	递归删除节点

1．启动客户端
$ bin/zkCli.sh
2．显示所有操作命令
[zk: localhost:2181(CONNECTED) 1] help
3．查看当前znode中所包含的内容
[zk: localhost:2181(CONNECTED) 0] ls /
[zookeeper]
4．查看当前节点详细数据
[zk: localhost:2181(CONNECTED) 1] ls2 /
[zookeeper]
cZxid = 0x0
ctime = Thu Jan 01 08:00:00 CST 1970
mZxid = 0x0
mtime = Thu Jan 01 08:00:00 CST 1970
pZxid = 0x0
cversion = -1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 0
numChildren = 1
5．分别创建2个普通节点
[zk: localhost:2181(CONNECTED) 3] create /sanguo "jinlian"
Created /sanguo
[zk: localhost:2181(CONNECTED) 4] create /sanguo/shuguo "liubei"
Created /sanguo/shuguo
6．获得节点的值
[zk: localhost:2181(CONNECTED) 5] get /sanguo
jinlian
cZxid = 0x100000003
ctime = Wed Aug 29 00:03:23 CST 2018
mZxid = 0x100000003
mtime = Wed Aug 29 00:03:23 CST 2018
pZxid = 0x100000004
cversion = 1
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 7
numChildren = 1
[zk: localhost:2181(CONNECTED) 6]
[zk: localhost:2181(CONNECTED) 6] get /sanguo/shuguo
liubei
cZxid = 0x100000004
ctime = Wed Aug 29 00:04:35 CST 2018
mZxid = 0x100000004
mtime = Wed Aug 29 00:04:35 CST 2018
pZxid = 0x100000004
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 6
numChildren = 0
7．创建短暂节点
[zk: localhost:2181(CONNECTED) 7] create -e /sanguo/wuguo "zhouyu"
Created /sanguo/wuguo
（1）在当前客户端是能查看到的
[zk: localhost:2181(CONNECTED) 3] ls /sanguo 
[wuguo, shuguo]
（2）退出当前客户端然后再重启客户端
[zk: localhost:2181(CONNECTED) 12] quit
$ bin/zkCli.sh
（3）再次查看根目录下短暂节点已经删除
[zk: localhost:2181(CONNECTED) 0] ls /sanguo
[shuguo]
8．创建带序号的节点
    （1）先创建一个普通的根节点/sanguo/weiguo
[zk: localhost:2181(CONNECTED) 1] create /sanguo/weiguo "caocao"
Created /sanguo/weiguo
    （2）创建带序号的节点
[zk: localhost:2181(CONNECTED) 2] create -s /sanguo/weiguo/xiaoqiao "jinlian"
Created /sanguo/weiguo/xiaoqiao0000000000
[zk: localhost:2181(CONNECTED) 3] create -s /sanguo/weiguo/daqiao "jinlian"
Created /sanguo/weiguo/daqiao0000000001
[zk: localhost:2181(CONNECTED) 4] create -s /sanguo/weiguo/diaocan "jinlian"
Created /sanguo/weiguo/diaocan0000000002
如果原来没有序号节点，序号从0开始依次递增。如果原节点下已有2个节点，则再排序时从2开始，以此类推。
9．修改节点数据值
[zk: localhost:2181(CONNECTED) 6] set /sanguo/weiguo "simayi"
10．节点的值变化监听
    （1）在hadoop104主机上注册监听/sanguo节点数据变化
[zk: localhost:2181(CONNECTED) 26] [zk: localhost:2181(CONNECTED) 8] get /sanguo watch
    （2）在hadoop103主机上修改/sanguo节点的数据
[zk: localhost:2181(CONNECTED) 1] set /sanguo "xisi"
    （3）观察hadoop104主机收到数据变化的监听
WATCHER::
WatchedEvent state:SyncConnected type:NodeDataChanged path:/sanguo
11．节点的子节点变化监听（路径变化）
    （1）在hadoop104主机上注册监听/sanguo节点的子节点变化
[zk: localhost:2181(CONNECTED) 1] ls /sanguo watch
[aa0000000001, server101]
    （2）在hadoop103主机/sanguo节点上创建子节点
[zk: localhost:2181(CONNECTED) 2] create /sanguo/jin "simayi"
Created /sanguo/jin
    （3）观察hadoop104主机收到子节点变化的监听
WATCHER::
WatchedEvent state:SyncConnected type:NodeChildrenChanged path:/sanguo
12．删除节点
[zk: localhost:2181(CONNECTED) 4] delete /sanguo/jin
13．递归删除节点
[zk: localhost:2181(CONNECTED) 15] rmr /sanguo/shuguo
14．查看节点状态
[zk: localhost:2181(CONNECTED) 17] stat /sanguo
cZxid = 0x100000003
ctime = Wed Aug 29 00:03:23 CST 2018
mZxid = 0x100000011
mtime = Wed Aug 29 00:21:23 CST 2018
pZxid = 0x100000014
cversion = 9
dataVersion = 1
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 4
numChildren = 1

4.3 API应用

4.3.1 环境搭建

1．创建一个Maven工程
2．添加pom文件
<dependencies>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.apache.logging.log4j</groupId>
            <artifactId>log4j-core</artifactId>
            <version>2.8.2</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.apache.zookeeper/zookeeper -->
        <dependency>
            <groupId>org.apache.zookeeper</groupId>
            <artifactId>zookeeper</artifactId>
            <version>3.4.10</version>
        </dependency>
</dependencies>
3．拷贝log4j.properties文件到项目根目录
需要在项目的src/main/resources目录下，新建一个文件，命名为“log4j.properties”，在文件中填入。
log4j.rootLogger=INFO, stdout  
log4j.appender.stdout=org.apache.log4j.ConsoleAppender  
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout  
log4j.appender.stdout.layout.ConversionPattern=%d %p [%c] - %m%n  
log4j.appender.logfile=org.apache.log4j.FileAppender  
log4j.appender.logfile.File=target/spring.log  
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout  
log4j.appender.logfile.layout.ConversionPattern=%d %p [%c] - %m%n  

4.3.2 创建ZooKeeper客户端

private static String connectString =
 "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zkClient = null;

    @Before
    public void init() throws Exception {

    zkClient = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

            @Override
            public void process(WatchedEvent event) {

                // 收到事件通知后的回调函数（用户的业务逻辑）
                System.out.println(event.getType() + "--" + event.getPath());

                // 再次启动监听
                try {
                    zkClient.getChildren("/", true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

4.3.3 创建子节点

// 创建子节点
@Test
public void create() throws Exception {
        // 参数1：要创建的节点的路径； 参数2：节点数据 ； 参数3：节点权限 ；参数4：节点的类型
        String nodeCreated = zkClient.create("/test", "jinlian".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}

4.3.4 获取子节点并监听节点变化

// 获取子节点
@Test
public void getChildren() throws Exception {

     List<String> children = zkClient.getChildren("/", true);

     for (String child : children) {
         System.out.println(child);
     }

     // 延时阻塞
     Thread.sleep(Long.MAX_VALUE);
}

4.3.5 判断Znode是否存在

// 判断znode是否存在
@Test
public void exist() throws Exception {

  Stat stat = zkClient.exists("/eclipse", false);

  System.out.println(stat == null ? "not exist" : "exist");
}

4.4 监听服务器节点动态上下线案例

具体实现
（0）先在集群上创建/servers节点
[zk: localhost:2181(CONNECTED) 10] create /servers "servers"
Created /servers
（1）服务器端向Zookeeper注册代码
package com.test.zkcase;
import java.io.IOException;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.ZooDefs.Ids;

public class DistributeServer {

    private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    private String parentNode = "/servers";
    
    // 创建到zk的客户端连接
    public void getConnect() throws IOException{
        
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

            @Override
            public void process(WatchedEvent event) {

            }
        });
    }
    
    // 注册服务器
    public void registServer(String hostname) throws Exception{

        String create = zk.create(parentNode + "/server", hostname.getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        
        System.out.println(hostname +" is online "+ create);
    }
    
    // 业务功能
    public void business(String hostname) throws Exception{
        System.out.println(hostname+" is working ...");
        
        Thread.sleep(Long.MAX_VALUE);
    }
    
    public static void main(String[] args) throws Exception {
        
// 1获取zk连接
        DistributeServer server = new DistributeServer();
        server.getConnect();
        
        // 2 利用zk连接注册服务器信息
        server.registServer(args[0]);
        
        // 3 启动业务功能
        server.business(args[0]);
    }
}
（2）客户端代码
package com.test.zkcase;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooKeeper;

public class DistributeClient {

    private static String connectString = "hadoop102:2181,hadoop103:2181,hadoop104:2181";
    private static int sessionTimeout = 2000;
    private ZooKeeper zk = null;
    private String parentNode = "/servers";

    // 创建到zk的客户端连接
    public void getConnect() throws IOException {
        zk = new ZooKeeper(connectString, sessionTimeout, new Watcher() {

            @Override
            public void process(WatchedEvent event) {

                // 再次启动监听
                try {
                    getServerList();
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    // 获取服务器列表信息
    public void getServerList() throws Exception {
        
        // 1获取服务器子节点信息，并且对父节点进行监听
        List<String> children = zk.getChildren(parentNode, true);

        // 2存储服务器信息列表
        ArrayList<String> servers = new ArrayList<>();
        
        // 3遍历所有节点，获取节点中的主机名称信息
        for (String child : children) {
            byte[] data = zk.getData(parentNode + "/" + child, false, null);

            servers.add(new String(data));
        }

        // 4打印服务器列表信息
        System.out.println(servers);
    }

    // 业务功能
    public void business() throws Exception{

        System.out.println("client is working ...");
Thread.sleep(Long.MAX_VALUE);
    }

    public static void main(String[] args) throws Exception {

        // 1获取zk连接
        DistributeClient client = new DistributeClient();
        client.getConnect();

        // 2获取servers的子节点信息，从中获取服务器信息列表
        client.getServerList();

        // 3业务进程启动
        client.business();
    }
}