Curator与zookeeper版本问题，分布式锁

一. Curator与zookeeper版本如下pom.xml

        
        
            org.apache.zookeeper
            zookeeper
            3.4.8
            pom
            
            
                
                    org.slf4j
                    slf4j-log4j12
                
            
        
        
            com.101tec
            zkclient
            0.7
        

        
        
            org.apache.curator
            curator-recipes
            4.2.0
            
                
                    zookeeper
                    org.apache.zookeeper
                
            
        

二. 分布式锁

分布式编程时，比如最容易碰到的情况就是应用程序在线上多机部署，于是当多个应用同时访问某一资源时，就需要某种机制去协调它们。例如，现在一台应用正在rebuild缓存内容，要临时锁住某个区域暂时不让访问；又比如调度程序每次只想一个任务被一台应用执行等等。

下面的程序会启动两个线程t1和t2去争夺锁，拿到锁的线程会占用5秒。运行多次可以观察到，有时是t1先拿到锁而t2等待，有时又会反过来。Curator会用我们提供的lock路径的结点作为全局锁，这个结点的数据类似这种格式：[_c_64e0811f-9475-44ca-aa36-c1db65ae5350-lock-0000000005]，每次获得锁时会生成这种串，释放锁时清空数据。

分布式锁测试代码：

package com.robinboot.facade.test;

import org.apache.curator.framework.recipes.locks.InterProcessMutex;
import org.apache.curator.retry.RetryNTimes;

import java.util.concurrent.TimeUnit;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;

/**
 * @auther: TF12778
 * @date: 2020/7/15 10:37
 * @description: Curator framework's distributed lock test.
 *
 * https://blog.csdn.net/robinson_911/article/details/107357978
 */
public class CuratorDistrLockTest {

    /** Zookeeper info */
    private static final String ZK_ADDRESS = "localhost:2181";
    private static final String ZK_LOCK_PATH = "/zktest";

    public static void main(String[] args) throws InterruptedException {
        // 1.Connect to zk
        CuratorFramework client = CuratorFrameworkFactory.newClient(
                ZK_ADDRESS,
                new RetryNTimes(10, 5000)
        );
        client.start();
        System.out.println("zk client start successfully!");

        Thread t1 = new Thread(() -> {
            doWithLock(client);
        }, "t1");
        Thread t2 = new Thread(() -> {
            doWithLock(client);
        }, "t2");

        t1.start();
        t2.start();
    }

    private static void doWithLock(CuratorFramework client) {
        InterProcessMutex lock = new InterProcessMutex(client, ZK_LOCK_PATH);
        try {
            if (lock.acquire(10 * 1000, TimeUnit.SECONDS)) {
                System.out.println(Thread.currentThread().getName() + " hold lock");
                Thread.sleep(5000L);
                System.out.println(Thread.currentThread().getName() + " release lock");
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                lock.release();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

输出的日志：

参考：https://www.cnblogs.com/erbing/p/9799098.html

https://blog.csdn.net/weixin_44565095/article/details/100619725