如何在CentOS上使用Zookeeper管理分布式锁

在CentOS上使用Zookeeper管理分布式锁，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。

下载并解压Zookeeper

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

配置Zookeeper

复制示例配置文件并进行必要的修改：

cp conf/zoo_sample.cfg conf/zoo.cfg

编辑conf/zoo.cfg文件，确保配置如下：

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

启动Zookeeper

bin/zkServer.sh start

2. 使用Zookeeper实现分布式锁

你可以使用Java客户端库来实现分布式锁。以下是一个简单的示例代码：

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);
            if (lockPath.endsWith(children.get(0))) {
                // We have the lock
                return;
            } else {
                // Wait for the node to be deleted
                String watchNode = null;
                for (String child : children) {
                    if (lockPath.endsWith(child)) {
                        watchNode = child;
                        break;
                    }
                }
                Stat stat = zk.exists(LOCK_ROOT + "/" + watchNode, true);
                if (stat == null) {
                    continue;
                }
                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();
            // Critical section
            System.out.println("Lock acquired");
            Thread.sleep(5000);
            lock.unlock();
            System.out.println("Lock released");
            lock.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3. 运行示例代码

编译并运行上述Java代码，确保Zookeeper服务正在运行并且可以连接。

javac DistributedLock.java
java DistributedLock

通过以上步骤，你可以在CentOS上使用Zookeeper实现分布式锁。这个示例代码展示了如何创建一个简单的分布式锁，并在临界区执行一些操作。你可以根据实际需求进行扩展和优化。