Zookeeper实战之分布式锁

Zookeeper实战之分布式锁

最近整理资料的时候发现了两年前自己写的一些Zookeeper的例子，今天整理了一下，放到这里，也许以后用的着。

首先准备一个Zookeeper集群环境，这里使用单机模拟集群环境，并使用代码方式启动服务。

Zookeeper服务

这里假定启动三个Zookeeper服务做集群

package my.zookeeperstudy;

import org.apache.commons.io.FileUtils;
import org.apache.zookeeper.server.quorum.QuorumPeerConfig;
import org.apache.zookeeper.server.quorum.QuorumPeerMain;

import java.io.File;
import java.net.InetAddress;
import java.util.Properties;

public class ZKServer {
    protected String id = null;
    protected String dataDir = null;
    protected String clientPort = null;

    public ZKServer(String id, String dataDir, String clientPort) {
        this.id = id;
        this.dataDir = dataDir;
        this.clientPort = clientPort;
    }

    public void startServer() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Properties props = new Properties();
                    props.setProperty("tickTime", "2000");
                    props.setProperty("dataDir", dataDir);
                    FileUtils.write(new File(props.getProperty("dataDir"), "myid"), id);
                    props.setProperty("clientPort", clientPort);
                    props.setProperty("initLimit", "10");
                    props.setProperty("syncLimit", "5");
                    String hostname = InetAddress.getLocalHost().getHostName();
                    props.setProperty("server.1", hostname + ":2881:3881");
                    props.setProperty("server.2", hostname + ":2882:3882");
                    props.setProperty("server.3", hostname + ":2883:3883");

                    QuorumPeerConfig quorumConfig = new QuorumPeerConfig();
                    quorumConfig.parseProperties(props);

                    QuorumPeerMain quorumPeerMain = new QuorumPeerMain();
                    quorumPeerMain.runFromConfig(quorumConfig);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

}

package my.zookeeperstudy;

public class ZKServer1 {

    public static void main(String[] args) throws Exception {
        ZKServer zkServer = new ZKServer("1", "/tmp/zookeeper1/data", "2181");
        zkServer.startServer();
    }

}

package my.zookeeperstudy;

public class ZKServer2 {

    public static void main(String[] args) throws Exception {
        ZKServer zkServer = new ZKServer("2", "/tmp/zookeeper2/data", "2182");
        zkServer.startServer();
    }

}

package my.zookeeperstudy;

public class ZKServer3 {

    public static void main(String[] args) throws Exception {
        ZKServer zkServer = new ZKServer("3", "/tmp/zookeeper3/data", "2183");
        zkServer.startServer();
    }

}

分布式锁类DistributedLocker

package my.zookeeperstudy.lock;

import org.apache.zookeeper.*;

import java.util.Collections;
import java.util.List;

public class DistributedLocker {
    private final ZooKeeper zk;
    private final String lockBasePath;
    private final String lockName;
    private String lockPath;

    public DistributedLocker(ZooKeeper zk, String lockBasePath, String lockName) {
        this.zk = zk;
        this.lockBasePath = lockBasePath;
        this.lockName = lockName;
    }

    public void getLock() throws KeeperException, InterruptedException {
        if (zk.exists(lockBasePath, true) == null) {
            zk.create(lockBasePath, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }
        lockPath = zk.create(lockBasePath + "/" + lockName, null, ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        System.out.println("getLock path: " + lockPath);
        final Object lock = new Object();
        synchronized (lock) {
            while (true) {
                List<String> nodes = zk.getChildren(lockBasePath, new Watcher() {
                    @Override
                    public void process(WatchedEvent event) {
                        synchronized (lock) {
                            lock.notifyAll();
                        }
                    }
                });
                Collections.sort(nodes);
                System.out.println(nodes);
                if (lockPath.endsWith(nodes.get(0))) {
                    return;
                } else {
                    lock.wait();
                }
            }
        }
    }

    public void releaseLock() throws KeeperException, InterruptedException {
        zk.delete(lockPath, -1);
        lockPath = null;
    }
}

测试客户端类

这里仍然模拟有三个客户端

package my.zookeeperstudy.lock;

import org.apache.zookeeper.*;

public class ZKClient {
    private final String lockBasePath = "/mylocks";
    private final String lockName = "mylock";

    public void start(String url) throws Exception {
        final ZooKeeper zk = new ZooKeeper(url, 10000, new Watcher() {
            public void process(WatchedEvent event) {
                System.out.println("event: " + event.getType());
            }
        });

        try {
            DistributedLocker locker = new DistributedLocker(zk, lockBasePath, lockName);

            System.out.println("before get lock");
            locker.getLock();
            System.out.println("after get lock");

            System.out.println("do something");
            Thread.sleep(60 * 1000);

            System.out.println("before release lock");
            locker.releaseLock();
            System.out.println("after release lock");
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

}

package my.zookeeperstudy.lock;

public class ZKClient1 {
    public static void main(String[] args) throws Exception {
        ZKClient zkClient = new ZKClient();
        zkClient.start("localhost:2181");
    }
}

package my.zookeeperstudy.lock;

public class ZKClient2 {
    public static void main(String[] args) throws Exception {
        ZKClient zkClient = new ZKClient();
        zkClient.start("localhost:2182");
    }
}

package my.zookeeperstudy.lock;

public class ZKClient3 {
    public static void main(String[] args) throws Exception {
        ZKClient zkClient = new ZKClient();
        zkClient.start("localhost:2183");
    }
}

测试

• 首先依次启动ZKServer1，ZKServer2和ZKServer3，启动过程会有错误，可以忽略，那是因为检测别的节点的时候连接失败导致，生产环境可以针对具体情况忽略此类错误。

• 然后依次启动ZKClient1，ZKClient2和ZKClient3。

• 分别观察三个Client日志输出。

• 停止一个Client比如ZKClient1然后观察日志输出。

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