简介

  在分布式环境下，为了防止多个服务同时修改同一个值，出现数据同步问题，通常用redis和zookeeper做分布式锁，在这里我们用zookeeper做分布式锁，并和单点环境中ReenTranLock锁相比较

1、ReenTranLock

 

package bjsxt.curator.lock;import java.util.concurrent.CountDownLatch;import java.util.concurrent.locks.ReentrantLock;public class Lock1 {    static ReentrantLock reentrantLock = new ReentrantLock();    static int count = 10;    public static void genarNo(){        try {            reentrantLock.lock();            count--;            System.out.println(count);        } finally {            reentrantLock.unlock();        }    }        public static void main(String[] args) throws Exception{                final CountDownLatch countdown = new CountDownLatch(1);        for(int i = 0; i < 10; i++){            new Thread(new Runnable() {                @Override                public void run() {                    try {                        countdown.await();                        genarNo();                    } catch (Exception e) {                        e.printStackTrace();                    } finally {                    }                }            },"t" + i).start();        }        Thread.sleep(50);        countdown.countDown();            }}

 

• 结果

9876543210

• 说明
• 本类开启了十个线程，来操作count值，从结果可以看出是线程安全的

2、zookeeper分布锁InterProcessMutex

package bjsxt.curator.lock;import java.text.SimpleDateFormat;import java.util.Date;import java.util.concurrent.CountDownLatch;import org.apache.curator.RetryPolicy;import org.apache.curator.framework.CuratorFramework;import org.apache.curator.framework.CuratorFrameworkFactory;import org.apache.curator.framework.recipes.locks.InterProcessMutex;import org.apache.curator.retry.ExponentialBackoffRetry;public class Lock2 {    /** zookeeper地址 */    static final String CONNECT_ADDR = "192.168.0.4:2181,192.168.0.9:2181,192.168.0.6:2181";    /** session超时时间 */    static final int SESSION_OUTTIME = 5000;        static int count = 10;    public static void genarNo(){        try {            count--;            System.out.println(count);        } finally {                }    }        public static void main(String[] args) throws Exception {                //1 重试策略：初试时间为1s 重试10次        RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 10);        //2 通过工厂创建连接        CuratorFramework cf = CuratorFrameworkFactory.builder()                    .connectString(CONNECT_ADDR)                    .sessionTimeoutMs(SESSION_OUTTIME)                    .retryPolicy(retryPolicy)//                    .namespace("super")                    .build();        //3 开启连接        cf.start();                //4 分布式锁        final InterProcessMutex lock = new InterProcessMutex(cf, "/super");        final CountDownLatch countdown = new CountDownLatch(1);                for(int i = 0; i < 10; i++){            new Thread(new Runnable() {                @Override                public void run() {                    try {                        countdown.await();                        //加锁                        lock.acquire();                        //-------------业务处理开始                        genarNo();                        //-------------业务处理结束                    } catch (Exception e) {                        e.printStackTrace();                    } finally {                        try {                            //释放                            lock.release();                        } catch (Exception e) {                            e.printStackTrace();                        }                    }                }            },"t" + i).start();        }        Thread.sleep(100);        countdown.countDown();    }}

• 结果
• 9876543210

  说明：

• 本类用InterProcessMutex做分布式锁，通过zookeeper节点不能重复的原理来让分布式环境的服务排队处理同一个数据