curator教程二——分布式鎖

簡介

  在分布式環境下，為了防止多個服務同時修改同一個值，出現數據同步問題，通常用redis和zookeeper做分布式鎖，在這里我們用zookeeper做分布式鎖，並和單點環境中ReenTranLock鎖相比較

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();

        
    }
}

 

• 結果

9
8
7
6
5
4
3
2
1
0

• 說明
• 本類開啟了十個線程，來操作count值，從結果可以看出是線程安全的

2、zookeeper分布鎖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超時時間 */
    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 重試策略：初試時間為1s 重試10次
        RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 10);
        //2 通過工廠創建連接
        CuratorFramework cf = CuratorFrameworkFactory.builder()
                    .connectString(CONNECT_ADDR)
                    .sessionTimeoutMs(SESSION_OUTTIME)
                    .retryPolicy(retryPolicy)
//                    .namespace("super")
                    .build();
        //3 開啟連接
        cf.start();
        
        //4 分布式鎖
        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();
                        //加鎖
                        lock.acquire();
                        //-------------業務處理開始
                        genarNo();
                        //-------------業務處理結束
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        try {
                            //釋放
                            lock.release();
                        } catch (Exception e) {
                            e.printStackTrace();
                        }
                    }
                }
            },"t" + i).start();
        }
        Thread.sleep(100);
        countdown.countDown();
    }
}

• 結果

• 9
  8
  7
  6
  5
  4
  3
  2
  1
  0

  說明：

• 本類用InterProcessMutex做分布式鎖，通過zookeeper節點不能重復的原理來讓分布式環境的服務排隊處理同一個數據