分布式锁

在分布式环境中，为了保证数据的一致性，经常在程序运行的某个运行点。需要进行同步控制。

package master;import java.text.SimpleDateFormat;import java.util.Date;import java.util.concurrent.CountDownLatch;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.framework.recipes.locks.InterProcessLock;import org.apache.curator.framework.recipes.locks.InterProcessMultiLock;import org.apache.curator.framework.recipes.locks.InterProcessMutex;import org.apache.curator.retry.ExponentialBackoffRetry;public class Recipes_Lock {        static String lock_path="/lock_paht";    static CuratorFramework client = CuratorFrameworkFactory.builder().            connectString("192.168.64.60:2181")            .connectionTimeoutMs(5000).            retryPolicy(new ExponentialBackoffRetry(3000, 3))            .build();        public static void main(String[] args) {        client.start();        final InterProcessMutex lock= new InterProcessMutex(client,lock_path);        final CountDownLatch down = new CountDownLatch(1);                for (int i = 0; i <30; i++) {            new Thread(new  Runnable() {                public void run() {                    try {                        down.wait();                        lock.acquire();                    } catch (InterruptedException e) {                        // TODO Auto-generated catch block                        e.printStackTrace();                    } catch (Exception e) {                        // TODO Auto-generated catch block                        e.printStackTrace();                    }                    SimpleDateFormat dateFormat = new SimpleDateFormat("HH:mm:ss|SSS");                    String orderNo = dateFormat.format(new Date());                    System.out.println("生成的订单号是："+orderNo);                    try {                        lock.release();                    } catch (Exception e) {                        // TODO Auto-generated catch block                        e.printStackTrace();                    }                }            }).start();;                    }        down.countDown();    }}

 上面这个程序借助Curator来实现了一个简单的分布式锁。其核心接口如下：

 

 

 工具

 curator也提供了了很多的工具类，其中用的最多的就是zkPath和EnsurePath。

ZKPaths

ZKPaths提供了一些简单的API来构建ZNode路径，递归创建和删除节点等，

 

package utils;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.retry.ExponentialBackoffRetry;import org.apache.curator.utils.ZKPaths;import org.apache.curator.utils.ZKPaths.PathAndNode;import org.apache.zookeeper.ZooKeeper;public class ZKPaths_sample {        static String path="/zkpath_path";    static CuratorFramework client = CuratorFrameworkFactory.builder().            connectString("192.168.64.60:2181")            .connectionTimeoutMs(5000).            retryPolicy(new ExponentialBackoffRetry(3000, 3))            .build();        public static void main(String[] args) throws Exception {        client.start();                ZooKeeper zooKeeper = client.getZookeeperClient().getZooKeeper();        System.out.println(ZKPaths.fixForNamespace(path, "sub"));        System.out.println(ZKPaths.makePath(path, "sub"));        System.out.println(ZKPaths.getNodeFromPath("zkapth_path/sub1"));                PathAndNode pn = ZKPaths.getPathAndNode("/zkpath_path/sub1");        System.out.println(pn.getPath());        System.out.println(pn.getNode());                ZKPaths.mkdirs(zooKeeper, path+"/child1");        ZKPaths.mkdirs(zooKeeper, path+"/child2");        System.out.println(ZKPaths.getSortedChildren(zooKeeper, path));            }    }

 

 EnsurePath

提供了一种能够确保数据及诶单存在的机制。

 

 

 TestingServer

 为了便于开发人员进行zookeeper的开发与测试，curator提供了一种启动简易的zookeeper服务器服务的方法

——TestingServer。TestingServer允许开发人员非常方便的启动一个标准的zookeeper服务器。并进行一系列的单元测试。

 

 TestingCluster

TestingCluster是一个可以模拟zookeeper集群环境的curator工具类，能够便于开发人员在本地模拟由

n台机器组成的集群环境。下面我们模拟一个有3台机器构成的zookeeper集群场景。