Zookeeper的学习

今天药忘吃喽~ 2022-12-08 14:25 181阅读 0赞

### 环境：linux，jdk，zookeeper ###

### 使用Java访问zookeeper时应该注意的问题： ###

**需要在windows的hosts里映射域名，即**

192.168.60.101 hadoop01
    192.168.60.102 hadoop02
    192.168.60.103 hadoop03

**即可访问成功！！！**

**注意：有些新装的windows10里吗，没有hosts文件，只需新建一个hosts文件即可。**

package application;
    
    import org.apache.zookeeper.CreateMode;
    import org.apache.zookeeper.ZooDefs;
    import org.apache.zookeeper.ZooKeeper;
    import org.apache.zookeeper.data.Stat;
    import org.junit.Before;
    import org.junit.Test;
    
    import java.nio.charset.StandardCharsets;
    import java.util.List;
    import java.util.concurrent.TimeUnit;
    
    /**
     * @author: wtl
     * @License: (C) Copyright 2020, wtl Corporation Limited.
     * @Contact: 1050100468@qq.com
     * @Date: 2020-09-20 9:31
     * @Version: 1.0
     * @Description:
     */
    public class Main {
    
        private ZooKeeper zkClient = null;
    
        @Before
        public void init() throws Exception {
            String connectString = "192.168.60.101:2181,192.168.60.102:2181,192.168.60.103:2181";
            zkClient = new ZooKeeper(connectString, 2000, (watchedEvent) -> {
                System.out.println(watchedEvent.getType() + ";" + watchedEvent.getPath() + ";" + watchedEvent.getState());
                try {
                    /*
                     * 由于监听只有一次有效，因此，在new Zookeeper()里的监听里写上zkClient.getChildren("/", true
                     */
                    zkClient.getChildren("/", true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            });
        }
    
        @Test
        public void create() throws Exception {
            String path = zkClient.create("/application", "hello,world".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            System.out.println(path);
        }
    
        @Test
        public void getChildren() throws Exception {
            /*
             * 由于监听只有一次有效，因此，在new Zookeeper()里的监听里写上zkClient.getChildren("/", true
             */
            List<String> children = zkClient.getChildren("/", true);
            children.forEach(System.out::println);
            TimeUnit.SECONDS.sleep(Integer.MAX_VALUE);
        }
    
        @Test
        public void testExist() throws Exception {
            Stat stat = zkClient.exists("/application", true);
            String existStr = null != stat ? "存在" : "不存在";
            System.out.println(existStr);
        }
    
        @Test
        public void getData() throws Exception {
            byte[] data = zkClient.getData("/app", true, new Stat());
            System.out.println(new String(data, StandardCharsets.UTF_8));
        }
    
        @Test
        public void deletePath() throws Exception {
            zkClient.delete("/app",-1);
        }
    
        @Test
        public void setData() throws Exception {
            Stat stat = zkClient.setData("/application", "hello,world!!!".getBytes(), -1);
            System.out.println(stat.getCtime() + ";" + stat.getCversion() + ";" + stat.getDataLength());
        }
    }

# zookeeper的业务场景： #

## 1、服务器上线和下线的时候客户的卷会感知到。 ##

### 亮点： ###

### 服务器端在注册节点时用的是：CreateMode.EPHEMERAL\_SEQUENTIAL，可以保证服务型下线时zookeeper能感知到。 ###

package application.service.zookeeper;
    
    import org.apache.zookeeper.CreateMode;
    import org.apache.zookeeper.ZooDefs;
    import org.apache.zookeeper.ZooKeeper;
    import org.apache.zookeeper.data.Stat;
    
    import java.util.List;
    import java.util.concurrent.TimeUnit;
    
    /**
     * @author: wtl
     * @License: (C) Copyright 2020, wtl Corporation Limited.
     * @Contact: 1050100468@qq.com
     * @Date: 2020-09-20 14:20
     * @Version: 1.0
     * @Description:
     */
    public class ZkServer {
        private static final String CONNECT_STRING = "192.168.60.101:2181,192.168.60.102:2181,192.168.60.103:2181";
        private static final int SESSION_TIME_OUT = 2000;
        private static final String PARENT_NODE_PATH = "/server";
        private static ZooKeeper zkClient = null;
    
        public static void main(String[] args) throws Exception {
            String hostname = args[0];
    
             zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIME_OUT, (watchedEvent) -> {
                 try {
                     List<String> children = zkClient.getChildren(PARENT_NODE_PATH, false);
                     System.out.println(children);
                 }
                 catch (Exception e){
                     e.printStackTrace();
                 }
             });
    
            //注册zookeeper上的节点
            Stat exists = zkClient.exists(PARENT_NODE_PATH, false);
            if (null == exists){
                zkClient.create(PARENT_NODE_PATH,"server".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
            registerZk(zkClient,hostname);
    
            //业务场景上线
            doWork(hostname);
    
            TimeUnit.SECONDS.sleep(Long.MAX_VALUE);
        }
    
        /**
         * 注册到zookeeper
         * @param hostname 主机名
         * @throws Exception 异常
         */
        private static void registerZk(ZooKeeper zkClient,String hostname) throws Exception {
            zkClient.create(PARENT_NODE_PATH + "/" + hostname,hostname.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);
        }
    
        //业务场景
        private static void doWork(String hostname){
            System.out.println(hostname + "业务场景上线了......");
        }
    }

package application.service.zookeeper;
    
    import org.apache.zookeeper.ZooKeeper;
    
    import java.io.IOException;
    import java.util.List;
    import java.util.concurrent.TimeUnit;
    
    /**
     * @author: wtl
     * @License: (C) Copyright 2020, wtl Corporation Limited.
     * @Contact: 1050100468@qq.com
     * @Date: 2020-09-20 14:35
     * @Version: 1.0
     * @Description:
     */
    public class ZkClient {
        private static ZooKeeper zkClient = null;
        private static final String CONNECT_STRING = "192.168.60.101:2181,192.168.60.102:2181,192.168.60.103:2181";
        private static final int SESSION_TIME_OUT = 2000;
        private static final String PARENT_NODE_PATH = "/server";
    
    
        public static void main(String[] args) throws Exception {
            zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIME_OUT, (watchedEvent) -> {
                try {
                    List<String> children = zkClient.getChildren(PARENT_NODE_PATH, true);
                    System.out.println(children);
                }
                catch (Exception e){
                    e.printStackTrace();
                }
            });
    
            //获取注册信息
            List<String> children = zkClient.getChildren(PARENT_NODE_PATH, true);
            System.out.println(children);
    
            TimeUnit.SECONDS.sleep(Long.MAX_VALUE);
        }
    }

## 2、客户端对服务器随机访问。 ##

### 亮点： ###

### 服务器端在注册节点时用的是：UUID和list.stream().sorted().collect(); ###

package application.service.zookeeper;
    
    import org.apache.zookeeper.CreateMode;
    import org.apache.zookeeper.Watcher;
    import org.apache.zookeeper.ZooDefs.Ids;
    import org.apache.zookeeper.ZooKeeper;
    import org.apache.zookeeper.data.Stat;
    
    import java.util.Comparator;
    import java.util.List;
    import java.util.UUID;
    import java.util.concurrent.TimeUnit;
    import java.util.stream.Collectors;
    
    /**
     * @author: wtl
     * @License: (C) Copyright 2020, wtl Corporation Limited.
     * @Contact: 1050100468@qq.com
     * @Date: 2020-09-20 15:24
     * @Version: 1.0
     * @Description:
     */
    public class RRServerChoice {
        private ZooKeeper zkClient = null;
        private static final String CONNECT_STRING = "192.168.60.101:2181,192.168.60.102:2181,192.168.60.103:2181";
        private static final int SESSION_TIME_OUT = 2000;
        private static final String PARENT_NODE_PATH = "/lock";
        private static String thisPath = null;
        public static void main(String[] args) throws Exception {
            RRServerChoice rrServerChoice = new RRServerChoice();
            rrServerChoice.connectZookeeper(args[0]);
            rrServerChoice.registerZookeeper(args[0]);
            TimeUnit.SECONDS.sleep(Long.MAX_VALUE);
        }
    
        /**
         * 每个server都会连接zookeeper
         * @throws Exception 异常
         */
        public void connectZookeeper(String hostname) throws Exception {
            zkClient = new ZooKeeper(CONNECT_STRING, SESSION_TIME_OUT, (watchedEvent) -> {
                try {
                    System.out.println(watchedEvent);
                    if (watchedEvent.getType() == Watcher.Event.EventType.NodeChildrenChanged){
                        List<String> children = zkClient.getChildren(PARENT_NODE_PATH, true);
                        List<String> stringList = children.stream().
                                map(s -> {
                                    return s.replaceAll(hostname+"-","");
                                }).sorted(Comparator.comparing(String::toString).reversed()).collect(Collectors.toList());
    
                        System.out.println(stringList);
                        System.out.println(thisPath);
    
                        if (0 == stringList.indexOf(thisPath.split("/")[2].replaceAll(hostname + "-",""))){
                            doSomething(hostname);
                        }
                    }
                }
                catch (Exception e){
                    e.printStackTrace();
                }
            });
        }
    
        /**
         *
         */
        public void registerZookeeper(String hostname) throws Exception {
            Stat exists = zkClient.exists(PARENT_NODE_PATH, false);
            if (null == exists){
                zkClient.create(PARENT_NODE_PATH,"lock".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
    
            //进行选举
            zkClient.getChildren(PARENT_NODE_PATH,true);
            String uuid = UUID.randomUUID().toString();
            thisPath = zkClient.create(PARENT_NODE_PATH + "/" + hostname + "-" + uuid,hostname.getBytes(),Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL);
        }
    
        public void doSomething(String hostname) throws Exception {
            System.out.println(hostname + ":" + thisPath + "拿到了锁" + ";"  + System.nanoTime());
            TimeUnit.SECONDS.sleep(2);
            zkClient.delete(thisPath,-1);
            registerZookeeper(hostname);
        }
    }