用zookeeper体验监听服务器是否还活着

丛网络上及视频里学习的代码稍微改编了一下, 配合自己的情况(三台zookeeper 虚拟机 HSlave1 HSlave2 HSlave3) ,模拟server挂掉后客户端得到的通知情况.

步骤

1. 启动三个Server的线程分别代表三台Server, 每个线程对应一台Server

2. 启动客户端,可以启动许多个,也可以只启动一个

3. 将一台Server 断线(在控制台用root账户执行shutdown now ),然后重新启动但不注册

4. 将另外2台Server依序断线

Server程序如下:

package chuangzhi;import org.apache.zookeeper.*; import java.io.IOException;public class DistributedServer_HSlave2 {private static String ServerName="HSlave2";private static String connectString="HSlave2:2181";private static int sessionTimeout=30000;private static final String parentNode="/servers";private ZooKeeper zk=null;public void getConnection(){try {zk=new ZooKeeper(connectString,sessionTimeout, new Watcher() {@Overridepublic void process(WatchedEvent watchedEvent) {System.out.println("path:"+watchedEvent.getPath()+"---type:"+watchedEvent.getType());try {zk.getChildren("/",true);} catch (KeeperException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}});} catch (IOException e) {e.printStackTrace();}}public void registerServer(String hostname) throws KeeperException, InterruptedException {if(zk.exists(parentNode,null)==null){;zk.create(parentNode,"pareth".getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT);}String path=zk.create(parentNode+"/server",hostname.getBytes(),ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.EPHEMERAL_SEQUENTIAL);System.out.println(hostname+"is online ..."+path);}public void handleBusiness(String hostname){System.out.println(hostname+"is working...");}public static void main(String[] args) throws KeeperException, InterruptedException {DistributedServer_HSlave2 server=new DistributedServer_HSlave2();server.getConnection();server.registerServer(ServerName);server.handleBusiness(ServerName);Thread.sleep(Long.MAX_VALUE);} }

Client端的代码

package chuangzhi;import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooKeeper;import java.io.IOException; import java.util.ArrayList; import java.util.List;public class DistributedClient {private static String connectString="HSlave1:2181,HSlave2:2181,HSlave3:2181";private static int sessionTimeout=30000;private static final String parentNode="/servers";public ZooKeeper zk;//volatile高并发private volatile List<String > serverList;public void getConnection(){try {zk=new ZooKeeper(connectString,sessionTimeout, new Watcher() {@Overridepublic void process(WatchedEvent watchedEvent) {try {getServerList();zk.getChildren("/",true);} catch (KeeperException e) {e.printStackTrace();} catch (InterruptedException e) {e.printStackTrace();}}});} catch (IOException e) {e.printStackTrace();}}public void getServerList() throws KeeperException, InterruptedException {List<String> children =zk.getChildren(parentNode,true);List<String> services=new ArrayList<String>();for(String child: children){byte[] bytes=zk.getData(parentNode+"/"+child,null,null);services.add(new String(bytes));}serverList=services;System.out.println(services);}public void handleBusiness() throws InterruptedException {System.out.println("client is working...");Thread.sleep(Long.MAX_VALUE);}public static void main(String[] args) throws KeeperException, InterruptedException {DistributedClient client=new DistributedClient();client.getConnection();client.getServerList();client.handleBusiness();} }
运行结果如下

[INFO ][2017/08/09 19:48:53915][org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:852)]
Socket connection established to HSlave1/192.168.100.23:2181, initiating session
[INFO ][2017/08/09 19:48:53931][org.apache.zookeeper.ClientCnxn$SendThread.onConnected(ClientCnxn.java:1235)]
Session establishment complete on server HSlave1/192.168.100.23:2181, sessionid = 0x15dc6cda23f0004, negotiated timeout = 30000

#三台服务器(HSlave1 HSlave2 HSlave3)上线, 每台服务器由一个程序建立节点

[HSlave3, HSlave2, HSlave1]

#客户端上线

client is working...
[HSlave3, HSlave2, HSlave1]

# 将HSlave2关机,客户端更新服务器列表

[HSlave3, HSlave1]

[INFO ][2017/08/09 19:53:09639][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1098)]
Unable to read additional data from server sessionid 0x15dc6cda23f0004, likely server has closed socket, closing socket connection and attempting reconnect
[INFO ][2017/08/09 19:53:09898][org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:975)]
Opening socket connection to server HSlave3/192.168.100.25:2181. Will not attempt to authenticate using SASL (unknown error)
[INFO ][2017/08/09 19:53:09899][org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:852)]
Socket connection established to HSlave3/192.168.100.25:2181, initiating session
[INFO ][2017/08/09 19:53:09903][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1098)]
Unable to read additional data from server sessionid 0x15dc6cda23f0004, likely server has closed socket, closing socket connection and attempting reconnect
org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /servers
at org.apache.zookeeper.KeeperException.create(KeeperException.java:99)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1472)
at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1500)
at chuangzhi.DistributedClient.getServerList(DistributedClient.java:57)
at chuangzhi.DistributedClient$1.process(DistributedClient.java:32)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:522)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:498)
[INFO ][2017/08/09 19:53:10583][org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:975)]
Opening socket connection to server HSlave2/192.168.100.24:2181. Will not attempt to authenticate using SASL (unknown error)
[INFO ][2017/08/09 19:53:10585]

# 将HSlave2重新开机并开启zkService

[org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:852)]
Socket connection established to HSlave2/192.168.100.24:2181, initiating session
[INFO ][2017/08/09 19:53:10586][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1098)]
Unable to read additional data from server sessionid 0x15dc6cda23f0004, likely server has closed socket, closing socket connection and attempting reconnect
[INFO ][2017/08/09 19:53:11841][org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:975)]
Opening socket connection to server HSlave1/192.168.100.23:2181. Will not attempt to authenticate using SASL (unknown error)
[INFO ][2017/08/09 19:53:21842][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1096)]
Client session timed out, have not heard from server in 11155ms for sessionid 0x15dc6cda23f0004, closing socket connection and attempting reconnect
[INFO ][2017/08/09 19:53:22629][org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:975)]
Opening socket connection to server HSlave3/192.168.100.25:2181. Will not attempt to authenticate using SASL (unknown error)
[INFO ][2017/08/09 19:53:22630][org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:852)]
Socket connection established to HSlave3/192.168.100.25:2181, initiating session
[INFO ][2017/08/09 19:53:22632][org.apache.zookeeper.ClientCnxn$SendThread.onConnected(ClientCnxn.java:1235)]

Session establishment complete on server HSlave3/192.168.100.25:2181, sessionid = 0x15dc6cda23f0004, negotiated timeout = 30000

# HSlave2已经重新开机并开启zkService,但没有运行程序建立节点, 服务器列表没有改变
[HSlave3, HSlave1]

# 将HSlave1关机,客户端更新服务器列表
[HSlave3]

# 将最后一台HSlave3也关机,客户端凌乱了(HSlave2维持开机并连接zkService)

[INFO ][2017/08/09 19:55:57207][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1098)]
Unable to read additional data from server sessionid 0x15dc6cda23f0004, likely server has closed socket, closing socket connection and attempting reconnect
[INFO ][2017/08/09 19:55:5850 ][org.apache.zookeeper.ClientCnxn$SendThread.logStartConnect(ClientCnxn.java:975)]
Opening socket connection to server HSlave2/192.168.100.24:2181. Will not attempt to authenticate using SASL (unknown error)
[INFO ][2017/08/09 19:55:5851 ][org.apache.zookeeper.ClientCnxn$SendThread.primeConnection(ClientCnxn.java:852)]
Socket connection established to HSlave2/192.168.100.24:2181, initiating session
[INFO ][2017/08/09 19:55:5852 ][org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1098)]
Unable to read additional data from server sessionid 0x15dc6cda23f0004, likely server has closed socket, closing socket connection and attempting reconnect
org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /servers
at org.apache.zookeeper.KeeperException.create(KeeperException.java:99)
at org.apache.zookeeper.KeeperException.create(KeeperException.java:51)
at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1472)
at org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1500)
at chuangzhi.DistributedClient.getServerList(DistributedClient.java:57)
at chuangzhi.DistributedClient$1.process(DistributedClient.java:32)
at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:522)
at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:498)

以下省略

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