CentOS如何利用Zookeeper实现分布式锁

在CentOS上利用Zookeeper实现分布式锁，可以按照以下步骤进行：

1. 安装Zookeeper

首先，你需要在CentOS上安装Zookeeper。你可以从Apache Zookeeper的官方网站下载最新版本的Zookeeper，并按照官方文档进行安装和配置。

安装步骤：

下载Zookeeper：

wget https://archive.apache.org/dist/zookeeper/zookeeper-3.7.0/apache-zookeeper-3.7.0-bin.tar.gz

解压文件：

tar -xzf apache-zookeeper-3.7.0-bin.tar.gz mv apache-zookeeper-3.7.0-bin /opt/zookeeper

配置Zookeeper：编辑/opt/zookeeper/conf/zoo.cfg文件，添加以下内容：

tickTime=2000 dataDir=/var/lib/zookeeper clientPort=2181 initLimit=5 syncLimit=2 server.1=localhost:2888:3888

创建数据目录：

mkdir -p /var/lib/zookeeper chown -R hadoop:hadoop /var/lib/zookeeper

启动Zookeeper：
```
/opt/zookeeper/bin/zkServer.sh start 
```

2. 实现分布式锁

你可以使用Zookeeper的临时顺序节点来实现分布式锁。以下是一个简单的Java示例，展示如何使用Zookeeper实现分布式锁。

添加依赖

在你的项目中添加Zookeeper客户端依赖（例如，使用Maven）：

<dependency> <groupId>org.apache.zookeeper</groupId> <artifactId>zookeeper</artifactId> <version>3.7.0</version> </dependency>

实现分布式锁

import org.apache.zookeeper.CreateMode; import org.apache.zookeeper.KeeperException; import org.apache.zookeeper.WatchedEvent; import org.apache.zookeeper.Watcher; import org.apache.zookeeper.ZooDefs; import org.apache.zookeeper.ZooKeeper; import org.apache.zookeeper.data.Stat; import java.io.IOException; import java.util.Collections; import java.util.List; public class DistributedLock { private static final String ZK_ADDRESS = "localhost:2181"; private static final int SESSION_TIMEOUT = 3000; private static final String LOCK_ROOT = "/locks"; private static final String LOCK_NODE = LOCK_ROOT + "/lock_"; private ZooKeeper zk; private String lockPath; public DistributedLock() throws IOException, InterruptedException, KeeperException { zk = new ZooKeeper(ZK_ADDRESS, SESSION_TIMEOUT, new Watcher() { @Override public void process(WatchedEvent event) { // Do nothing for now } }); // Ensure the root lock node exists Stat stat = zk.exists(LOCK_ROOT, false); if (stat == null) { zk.create(LOCK_ROOT, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT); } } public void lock() throws KeeperException, InterruptedException { lockPath = zk.create(LOCK_NODE, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL); while (true) { List<String> children = zk.getChildren(LOCK_ROOT, false); Collections.sort(children); String smallestChild = children.get(0); if (lockPath.endsWith(smallestChild)) { // We have the lock return; } else { // Wait for the node to be deleted int index = Collections.binarySearch(children, lockPath.substring(LOCK_ROOT.length() + 1)); String watchNode = LOCK_ROOT + "/" + children.get(index - 1); Stat stat = zk.exists(watchNode, new Watcher() { @Override public void process(WatchedEvent event) { if (event.getType() == Event.EventType.NodeDeleted) { synchronized (this) { notifyAll(); } } } }); if (stat != null) { synchronized (this) { wait(); } } } } } public void unlock() throws KeeperException, InterruptedException { if (lockPath != null) { zk.delete(lockPath, -1); lockPath = null; } } public void close() throws InterruptedException { zk.close(); } public static void main(String[] args) { try { DistributedLock lock = new DistributedLock(); lock.lock(); System.out.println("Lock acquired"); // Perform some critical section operations lock.unlock(); System.out.println("Lock released"); lock.close(); } catch (Exception e) { e.printStackTrace(); } } }

3. 运行示例

编译并运行上述Java程序，确保Zookeeper服务正在运行。

javac -cp .:zookeeper-3.7.0.jar DistributedLock.java java -cp .:zookeeper-3.7.0.jar DistributedLock

通过以上步骤，你可以在CentOS上利用Zookeeper实现分布式锁。这个示例展示了如何创建临时顺序节点并监视前一个节点的删除事件，从而实现锁的获取和释放。