zookeeper如何实现服务节点,集群的管理

一.zookeeper如何实现服务节点,集群的管理

Zookeeper使用实例——服务节点管理
分布式处理中，总会存在多个服务节点同时工作，并且节点数量会随着网络规模的变化而动态增减，服务节点也有可能发生宕机与恢复。面对着动态增减的服务节点，我们如何保证客户请求被服务器正确处理呢。我们可以通过zookeeper临时节点创建与自动删除来掌握服务节点的动态增减。

思路为:

1. zookeeper 的apach jar包依赖支持 在zookeeper创建临时节点,当session断开时,自动删除临时节点
2. zookeeper 的apach jar包依赖支持 有监听器模式,能够监听到 临时节点的增加与删除

1、 服务器启动后 在zookeeper创建 (与session同步的 )临时目录

package com.coshaho.learn.zookeeper;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;

/**
*
* 服务节点启动后注册到zookeeper
* @author coshaho
*
*/
public class AppServer extends Thread
{
private String clusterNode = "Locks";
private String serverNode = "mylock";
private String serverName;
private long sleepTime;

public void run()
{
try
{
connectZookeeper(serverName);
}
catch (Exception e)
{
e.printStackTrace();
}
}
public void connectZookeeper(String address) throws Exception
{
ZooKeeper zk = new ZooKeeper("192.168.1.104:12181", 5000, new Watcher()
{
public void process(WatchedEvent event)
{}
});

// 关键方法，创建包含自增长id名称的目录，这个方法支持了分布式锁的实现
// 四个参数：
// 1、目录名称 2、目录文本信息
// 3、文件夹权限，Ids.OPEN_ACL_UNSAFE表示所有权限
// 4、目录类型，CreateMode.EPHEMERAL_SEQUENTIAL表示创建临时目录，session断开连接则目录自动删除
String createdPath = zk.create(
"/" + clusterNode + "/" + serverNode,
address.getBytes("utf-8"),
Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
System.out.println("create: " + createdPath);
Thread.sleep(sleepTime);
}

public AppServer(String serverName, long sleepTime)
{
this.serverName = serverName;
this.sleepTime = sleepTime;
}
}

2、 节点管理服务 监听zookeeper 临时目录节点 创建,删除事件

package com.coshaho.learn.zookeeper;

import java.util.ArrayList;
import java.util.List;

import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.EventType;
import org.apache.zookeeper.ZooKeeper;

/**
*
* 客户端注册监听server节点变化
* @author coshaho
*
*/
public class AppMaster
{
private String clusterNode = "Locks";
private ZooKeeper zk;
private volatile List<String> serverList;

public void connectZookeeper() throws Exception
{
// 注册全局默认watcher
zk = new ZooKeeper("192.168.1.104:12181", 5000, new Watcher()
{
public void process(WatchedEvent event)
{
if (event.getType() == EventType.NodeChildrenChanged
&& ("/" + clusterNode).equals(event.getPath()))
{
try
{
updateServerList();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
});

updateServerList();
}

private void updateServerList() throws Exception
{
List<String> newServerList = new ArrayList<String>();

// watcher注册后，只能监听事件一次，参数true表示继续使用默认watcher监听事件
List<String> subList = zk.getChildren("/" + clusterNode, true);
for (String subNode : subList)
{
// 获取节点数据
byte[] data = zk.getData("/" + clusterNode + "/" + subNode, false, null);
newServerList.add(new String(data, "utf-8"));
}

serverList = newServerList;
System.out.println("server list updated: " + serverList);
}

public static void main(String[] args) throws Exception
{
AppMaster ac = new AppMaster();
ac.connectZookeeper();
Thread.sleep(Long.MAX_VALUE);
}
}

3、 启动两个服务器 进行测试

package com.coshaho.learn.zookeeper;

public class Server1
{
public static void main(String[] args) throws Exception
{
AppServer server1 = new AppServer("Server1", 5000);
server1.start();
}
}

package com.coshaho.learn.zookeeper;

public class Server2
{
public static void main(String[] args) throws Exception
{
AppServer server1 = new AppServer("Server2", 10000);
server1.start();
}
}

4、 运行结果

log4j:WARN No appenders could be found for logger (org.apache.zookeeper.ZooKeeper).
log4j:WARN Please initialize the log4j system properly.
log4j:WARN See http://logging.apache.org/log4j/1.2/faq.html#noconfig for more info.
server list updated: []
server list updated: [Server1]
server list updated: [Server2, Server1]
server list updated: [Server2]
server list updated: []

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