Zookeeper入门实战(5)-分布式锁

在分布式环境中，当需要控制对某一资源的不同进程并发访问时就需要使用分布式锁；可以使用 ZooKeeper + Curator 来实现分布式锁，本文主要介绍 Curator 中分布式锁的使用，文中所使用到的软件版本：Java 1.8.0_341、Zookeeper 3.7.1、curator 5.4.0。

1、引入依赖

<dependency>
    <groupId>org.apache.curator</groupId>
    <artifactId>curator-recipes</artifactId>
    <version>5.4.0</version>
</dependency>

2、使用样例

2.1、可重入锁

@Test
public void interProcessMutex() throws InterruptedException {
    CuratorFramework cf = getCuratorFramework();
    cf.start();
    InterProcessLock lock = new InterProcessMutex(cf, "/test/lock");
    int size = 5;
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
        new Thread(() -> {
            try {
                lock.acquire();
                //同一线程中可重复获取
                lock.acquire();
                logger.info(Thread.currentThread().getName() + "获得了锁");
                Thread.sleep(1000 * 3);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                //获取了几次就要释放几次
                release(lock);
                release(lock);
                logger.info(Thread.currentThread().getName() + "释放了锁");
            }
            countDownLatch.countDown();
        }).start();
    }
    countDownLatch.await();
    cf.close();
}

2.2、不可重入锁

@Test
public void interProcessSemaphoreMutex() throws InterruptedException {
    CuratorFramework cf = getCuratorFramework();
    cf.start();
    InterProcessLock lock = new InterProcessSemaphoreMutex(cf, "/test/lock2");
    int size = 5;
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
        new Thread(() -> {
            try {
                lock.acquire();
                //同一线程中不可重复获取
                //lock.acquire();
                logger.info(Thread.currentThread().getName() + "获得了锁");
                Thread.sleep(1000 * 3);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                release(lock);
                logger.info(Thread.currentThread().getName() + "释放了锁");
            }
            countDownLatch.countDown();
        }).start();
    }
    countDownLatch.await();
    cf.close();
}

2.3、读写锁(可重入)

@Test
public void interProcessReadWriteLock() throws InterruptedException {
    CuratorFramework cf = getCuratorFramework();
    InterProcessReadWriteLock lock = new InterProcessReadWriteLock(cf, "/test/lock3");
    InterProcessReadWriteLock.ReadLock readLock = lock.readLock();
    InterProcessReadWriteLock.WriteLock writeLock = lock.writeLock();

    cf.start();
    int size = 5;
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
        new Thread(() -> {
            try {
                readLock.acquire();
                readLock.acquire();
                logger.info(Thread.currentThread().getName() + "获得了读锁");
                Thread.sleep(1000 * 2);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                //获取了几次就要释放几次
                release(readLock);
                release(readLock);
                logger.info(Thread.currentThread().getName() + "释放了读锁");
            }
            try {
                writeLock.acquire();
                logger.info(Thread.currentThread().getName() + "获得了写锁");
                Thread.sleep(1000 * 2);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                release(writeLock);
                logger.info(Thread.currentThread().getName() + "释放了写锁");
            }
            countDownLatch.countDown();
        }).start();
    }
    countDownLatch.await();
    cf.close();
}

2.4、信号量

信号量用于控制对资源同时访问的进程或线程数。

@Test
public void interProcessSemaphoreV2() throws InterruptedException {
    CuratorFramework cf = getCuratorFramework();
    InterProcessSemaphoreV2 semaphore = new InterProcessSemaphoreV2(cf, "/test/lock4", 3);

    cf.start();
    int size = 5;
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
        new Thread(() -> {
            Lease lease = null;
            try {
                //获取一个许可
                lease = semaphore.acquire();
                logger.info(Thread.currentThread().getName() + "获得了许可");
                Thread.sleep(1000 * 3);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                //释放一个许可
                semaphore.returnLease(lease);
                logger.info(Thread.currentThread().getName() + "释放了许可");
            }
            countDownLatch.countDown();
        }).start();
    }
    countDownLatch.await();
    cf.close();
}

2.5、多个锁作为单个实体管理

InterProcessMultiLock 主要功能是将多个锁合并为一个对象来操作，简化了代码量。

@Test
public void InterProcessMultiLock() throws InterruptedException {
    CuratorFramework cf = getCuratorFramework();
    InterProcessLock lock = new InterProcessMutex(cf, "/test/lock");
    InterProcessLock lock2 = new InterProcessSemaphoreMutex(cf, "/test/lock2");
    InterProcessMultiLock multiLock = new InterProcessMultiLock(Arrays.asList(lock, lock2));

    cf.start();
    int size = 5;
    CountDownLatch countDownLatch = new CountDownLatch(size);
    for (int i = 0; i < size; i++) {
        new Thread(() -> {
            try {
                //相当于 lock.acquire() 和 lock2.acquire()
                multiLock.acquire();
                logger.info(Thread.currentThread().getName() + "获得了锁");
                Thread.sleep(1000 * 3);
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                release(multiLock);
                logger.info(Thread.currentThread().getName() + "释放了锁");
            }
            countDownLatch.countDown();
        }).start();
    }
    countDownLatch.await();
    cf.close();
}

 

分布式锁使用样例的完整代码如下：

package com.abc.demo.general.zookeeper;

import org.apache.curator.RetryPolicy;
import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.locks.*;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Arrays;
import java.util.concurrent.CountDownLatch;

public class CuratorLockCase {
    private static Logger logger = LoggerFactory.getLogger(CuratorLockCase.class);

    private static String connectString = "10.49.196.33:2181";
    private static int sessionTimeout = 40 * 1000;
    private static int connectionTimeout = 60 * 1000;

    /**
     * 可重入锁
     */
    @Test
    public void interProcessMutex() throws InterruptedException {
        CuratorFramework cf = getCuratorFramework();
        cf.start();
        InterProcessLock lock = new InterProcessMutex(cf, "/test/lock");
        int size = 5;
        CountDownLatch countDownLatch = new CountDownLatch(size);
        for (int i = 0; i < size; i++) {
            new Thread(() -> {
                try {
                    lock.acquire();
                    //同一线程中可重复获取
                    lock.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了锁");
                    Thread.sleep(1000 * 3);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    //获取了几次就要释放几次
                    release(lock);
                    release(lock);
                    logger.info(Thread.currentThread().getName() + "释放了锁");
                }
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();
        cf.close();
    }

    /**
     * 不可重入锁
     */
    @Test
    public void interProcessSemaphoreMutex() throws InterruptedException {
        CuratorFramework cf = getCuratorFramework();
        cf.start();
        InterProcessLock lock = new InterProcessSemaphoreMutex(cf, "/test/lock2");
        int size = 5;
        CountDownLatch countDownLatch = new CountDownLatch(size);
        for (int i = 0; i < size; i++) {
            new Thread(() -> {
                try {
                    lock.acquire();
                    //同一线程中不可重复获取
                    //lock.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了锁");
                    Thread.sleep(1000 * 3);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    release(lock);
                    logger.info(Thread.currentThread().getName() + "释放了锁");
                }
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();
        cf.close();
    }

    /**
     * 读写锁(可重入)
     */
    @Test
    public void interProcessReadWriteLock() throws InterruptedException {
        CuratorFramework cf = getCuratorFramework();
        InterProcessReadWriteLock lock = new InterProcessReadWriteLock(cf, "/test/lock3");
        InterProcessReadWriteLock.ReadLock readLock = lock.readLock();
        InterProcessReadWriteLock.WriteLock writeLock = lock.writeLock();

        cf.start();
        int size = 5;
        CountDownLatch countDownLatch = new CountDownLatch(size);
        for (int i = 0; i < size; i++) {
            new Thread(() -> {
                try {
                    readLock.acquire();
                    readLock.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了读锁");
                    Thread.sleep(1000 * 2);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    //获取了几次就要释放几次
                    release(readLock);
                    release(readLock);
                    logger.info(Thread.currentThread().getName() + "释放了读锁");
                }
                try {
                    writeLock.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了写锁");
                    Thread.sleep(1000 * 2);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    release(writeLock);
                    logger.info(Thread.currentThread().getName() + "释放了写锁");
                }
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();
        cf.close();
    }

    /**
     * 信号量，用于控制对资源同时访问的进程或线程数
     */
    @Test
    public void interProcessSemaphoreV2() throws InterruptedException {
        CuratorFramework cf = getCuratorFramework();
        InterProcessSemaphoreV2 semaphore = new InterProcessSemaphoreV2(cf, "/test/lock4", 3);

        cf.start();
        int size = 5;
        CountDownLatch countDownLatch = new CountDownLatch(size);
        for (int i = 0; i < size; i++) {
            new Thread(() -> {
                Lease lease = null;
                try {
                    //获取一个许可
                    lease = semaphore.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了许可");
                    Thread.sleep(1000 * 3);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    //释放一个许可
                    semaphore.returnLease(lease);
                    logger.info(Thread.currentThread().getName() + "释放了许可");
                }
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();
        cf.close();
    }


    /**
     * 多个锁作为单个实体管理
     */
    @Test
    public void InterProcessMultiLock() throws InterruptedException {
        CuratorFramework cf = getCuratorFramework();
        InterProcessLock lock = new InterProcessMutex(cf, "/test/lock");
        InterProcessLock lock2 = new InterProcessSemaphoreMutex(cf, "/test/lock2");
        InterProcessMultiLock multiLock = new InterProcessMultiLock(Arrays.asList(lock, lock2));

        cf.start();
        int size = 5;
        CountDownLatch countDownLatch = new CountDownLatch(size);
        for (int i = 0; i < size; i++) {
            new Thread(() -> {
                try {
                    //相当于 lock.acquire() 和 lock2.acquire()
                    multiLock.acquire();
                    logger.info(Thread.currentThread().getName() + "获得了锁");
                    Thread.sleep(1000 * 3);
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    release(multiLock);
                    logger.info(Thread.currentThread().getName() + "释放了锁");
                }
                countDownLatch.countDown();
            }).start();
        }
        countDownLatch.await();
        cf.close();
    }

    private CuratorFramework getCuratorFramework() {
        RetryPolicy retryPolicy  = new ExponentialBackoffRetry(1000, 3);
        CuratorFramework cf = CuratorFrameworkFactory.builder()
                .connectString(connectString)
                .sessionTimeoutMs(sessionTimeout)
                .connectionTimeoutMs(connectionTimeout)
                .retryPolicy(retryPolicy)
                .build();
        return cf;
    }

    private void release(InterProcessLock lock) {
        if (lock != null) {
            try {
                lock.release();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}