Curator简介
目前市面上实现分布式锁还是有很多种方案，zookeeper就是其中一种，但是原生的api特别难用，所以就有curator框架诞生了，它就是对zookeeper原生api的一种封装。 curator提供的是流式编程风格，做的非常不错，是目前使用率最高的一种zookeeper框架。实现起来也是非常的简单。
1、引入 pom依赖
在这里要注意一下，这里pom中使用的zk版本最好与zk连接中使用的版本一致
<!--zookeeper的客户端依赖-->
<dependency>
<groupId>org.apache.zookeeper</groupId>
<artifactId>zookeeper</artifactId>
<version>3.5.9</version>
</dependency>
<!--curator-->
<dependency>
<groupId>org.apache.curator</groupId>
<artifactId>curator-recipes</artifactId>
<version>4.0.1</version>
</dependency>
2、具体实现
使用curator实现分布式锁主要有三个步骤：
public class TestLock2 {
// zk临时节点的父目录
private static final String LOCK_PATH = "/testLock";
// 客户端的数量
private static final int CLIENT_NUMS = 3;
// 线程堵塞计数器
private static CountDownLatch countDownLatch = new CountDownLatch(CLIENT_NUMS);
@Test
public void myTest2() {
for (int i = 0; i < CLIENT_NUMS; i++) {
new Thread(new Runnable() {
@Override
public void run() {
// 重试策略(重试时间，重试次数)
RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3);
// 获取连接
CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1:2181", retryPolicy);
client.start();
try {
// 可重入锁，可以加入重入操作执行
final InterProcessMutex lock = new InterProcessMutex(client, LOCK_PATH);
// 可让每个客户端请求多次锁资源进行测试
for (int j = 1; j <= 1; j++) {
try {
// 调用acquire获取锁成功后会在/testLock下创建临时节点，节点名称类似与：_c_723c6b99-f0ec-4539-ada2-3e17a48746ed-lock-0000000309
if (lock.acquire(10, TimeUnit.SECONDS)) {
System.out.println(Thread.currentThread().getName() + " get lock 1 ...");
// 模拟业务操作
Thread.sleep(10);
System.out.println(Thread.currentThread().getName() + " do 1 ... ");
} else {
throw new IllegalStateException(Thread.currentThread().getName() + " get lock 1 timeout ");
}
// 获取可重入锁
if (lock.acquire(10, TimeUnit.SECONDS)) {
System.out.println(Thread.currentThread().getName() + " get lock 2 ...");
Thread.sleep(10);
System.out.println(Thread.currentThread().getName() + " do 2 ... ");
} else {
throw new IllegalStateException(Thread.currentThread().getName() + " get lock 2 timeout");
}
} finally {
// 在finally中释放锁，申请几次释放几次，调用release释放锁删除acquire产生的临时节点
System.out.println(Thread.currentThread().getName() + " release lock 2");
lock.release();
System.out.println(Thread.currentThread().getName() + " release lock 1");
lock.release();
}
}
} catch (Exception e) {
e.printStackTrace();
} finally {
CloseableUtils.closeQuietly(client);
countDownLatch.countDown();
}
}
}).start();
}
// 阻塞等待线程计数器归零
try {
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("end ...");
}
// 测试结果
/*
Thread-2 get lock 1 ...
Thread-2 do 1 ...
Thread-2 get lock 2 ...
Thread-2 do 2 ...
Thread-2 release lock 2
Thread-2 release lock 1
2021-01-25 13:36:31,874 [myid:] - INFO [Curator-Framework-0:CuratorFrameworkImpl@937] - backgroundOperationsLoop exiting
Thread-1 get lock 1 ...
Thread-1 do 1 ...
Thread-1 get lock 2 ...
Thread-1 do 2 ...
Thread-1 release lock 2
Thread-1 release lock 1
2021-01-25 13:36:31,914 [myid:] - INFO [Curator-Framework-0:CuratorFrameworkImpl@937] - backgroundOperationsLoop exiting
Thread-0 get lock 1 ...
Thread-0 do 1 ...
Thread-0 get lock 2 ...
Thread-0 do 2 ...
Thread-0 release lock 2
Thread-0 release lock 1
2021-01-25 13:36:31,963 [myid:] - INFO [Curator-Framework-0:CuratorFrameworkImpl@937] - backgroundOperationsLoop exiting
2021-01-25 13:36:32,010 [myid:] - INFO [Thread-2:ZooKeeper@1422] - Session: 0x1008587bbf70003 closed
2021-01-25 13:36:32,010 [myid:] - INFO [Thread-2-EventThread:ClientCnxn$EventThread@524] - EventThread shut down for session: 0x1008587bbf70003
2021-01-25 13:36:32,109 [myid:] - INFO [Thread-0:ZooKeeper@1422] - Session: 0x1008587bbf70004 closed
2021-01-25 13:36:32,109 [myid:] - INFO [Thread-0-EventThread:ClientCnxn$EventThread@524] - EventThread shut down for session: 0x1008587bbf70004
2021-01-25 13:36:32,209 [myid:] - INFO [Thread-1:ZooKeeper@1422] - Session: 0x1008587bbf70005 closed
end ...
*/
}
Curator主要从以下几个方面降低了zk使用的复杂性:
