如何在CentOS上使用Zookeeper进行分布式锁

在CentOS上使用Zookeeper进行分布式锁，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：

1. 下载Zookeeper：

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

2. 解压文件：

   tar -xzf apache-zookeeper-3.7.0-bin.tar.gz
   

3. 移动到合适的位置：

   mv apache-zookeeper-3.7.0-bin /opt/zookeeper
   

4. 创建数据和日志目录：

   mkdir -p /var/lib/zookeeper/data
   mkdir -p /var/log/zookeeper
   

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

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

6. 启动Zookeeper：

   /opt/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zookeeper-3.x.x.jar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（如果你使用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));
                Stat stat = zk.exists(LOCK_ROOT + "/" + children.get(index - 1), 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();
            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代码，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上使用Zookeeper实现分布式锁。