zookeeper应用：屏障、队列、分布式锁

zookeeper工具类：

获取连接实例；创建节点；获取子节点；设置节点数据；获取节点数据；访问控制等。

package org.windwant.zookeeper;

import org.apache.zookeeper.*;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;
import org.apache.zookeeper.server.auth.DigestAuthenticationProvider;

import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.util.List;

/**
 * zookeeper util
 */
public class ZookeeperUtil {
    private static final int SESSION_TIMEOUT = 30000;

    /**
     * 使用连接串创建连接
     * @param domain
     * @param w
     * @return
     */
    public static ZooKeeper getInstance(String domain, Watcher w){
        try {
            return new ZooKeeper(domain,SESSION_TIMEOUT, w);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }


    public static String createNode(ZooKeeper zk, String path, byte[] data){
        try {
            return zk.create(path, data, Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static List<String> getChildrenNode(ZooKeeper zk, String path){
        try {
            return zk.getChildren(path, false);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static Stat setNodeData(ZooKeeper zk, String path, byte[] data, int version){
        try {
            return zk.setData(path, data, version);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static byte[] getNodeData(ZooKeeper zk, String path){
        try {
            return zk.getData(path, false, null);
        } catch (KeeperException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }

    public static void deleteNode(ZooKeeper zk, String path, int version){
        try {
            zk.delete(path, version);
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }

    public static void closeZk(ZooKeeper zk){
        try {
            if(zk != null) {
                zk.close();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    public static void addAuth(ZooKeeper zk, String userName, String passwd){
        try {
            zk.addAuthInfo(String.valueOf(Ids.AUTH_IDS), DigestAuthenticationProvider.generateDigest(userName + ":" + passwd).getBytes());
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
//        try {
//            ZooKeeper zk = new ZooKeeper("localhost", 2181, null);
//            addAuth(zk, "roger", "123456");
//        } catch (IOException e) {
//            e.printStackTrace();
//        }
        try {
            System.out.println(DigestAuthenticationProvider.generateDigest("roger:123456"));
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
    }
}

继承父类：

SyncPrimitive

负责zookeeper连接及根节点的初始化。

实现zookeeper的Watcher

package org.windwant.zookeeper;

import org.apache.zookeeper.*;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class SyncPrimitive implements Watcher {

    protected ZooKeeper zk = null;
    protected Integer mutex;

    SyncPrimitive(Integer mutex) {
        this.mutex = mutex;
    }

    /**
     * 初始化zookeeper
     * @param domain
     */
    protected void initZK(String domain){
        System.out.println(Thread.currentThread().getName() + ": init zookeeper...");
        try {
            zk = new ZooKeeper(domain, 30000, this);
            System.out.println(Thread.currentThread().getName() + ": zookeeper connected " + zk);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * 初始化应用根节点 并发处理
     * @param root
     */
    protected void initZKRootNode(String root){
        //并发控制
        synchronized (mutex) {
            try {
                if (zk != null) {
                    if (zk.exists(root, false) != null) {
                        List<String> child = zk.getChildren(root, false);
                        if (child != null && !child.isEmpty()) {
                            //zookeeper multi操作；或者 Transaction（multi封装） commit操作；
                            List<Op> ops = new ArrayList<>();
                            child.forEach(c -> {
                                ops.add(Op.delete(root + "/" + c, -1));
                            });
                            List<OpResult> opRsts = zk.multi(ops);
                            System.out.println(Thread.currentThread().getName() + ": deleted child node success!");
                        }
                        zk.setData(root, String.valueOf(0).getBytes(), -1);
                        System.out.println(Thread.currentThread().getName() + ": app root node " + root + " init success! ");
                    } else {
                        zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,
                                CreateMode.PERSISTENT);
                        System.out.println(Thread.currentThread().getName() + ": app root node " + root + " create success! ");
                    }
                }
            } catch (KeeperException e) {
                e.printStackTrace();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void process(WatchedEvent event) {
        if(event.getState().equals(Event.KeeperState.SyncConnected)) {
        }
    }
}

zookeeper 屏障 Barrier：

SyncPrimitiveBarrier

enter()：加入屏障队列

leave()：离开屏障队列

package org.windwant.zookeeper;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;

import java.io.UnsupportedEncodingException;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

public class SyncPrimitiveBarrier extends SyncPrimitive {

    private String root;
    //屏障阈值
    private int size;
    private String name;

    /**
     * Barrier constructor
     *
     * @param domain
     * @param root
     * @param size
     */
    public SyncPrimitiveBarrier(String domain, String root, Integer size) {
        super(size);
        this.root = root;
        this.size = size;

        initZK(domain);
        initZKRootNode(root);

        // My node name
        try {
            name = new String(InetAddress.getLocalHost().getCanonicalHostName().toString());
        } catch (UnknownHostException e) {
            System.out.println(e.toString());
        }

    }

    /**
     * Join barrier
     *
     * @return
     * @throws KeeperException
     * @throws InterruptedException
     */

    boolean enter() throws KeeperException, InterruptedException{
        synchronized (mutex) {
            List<String> list = zk.getChildren(root, true);
            //当前节点数小于阈值，则创建节点，进入barrier
            if (list.size() < size) {
                System.out.println("node: " + list.size());
                this.name = zk.create(root + "/" + name, new byte[0], Ids.OPEN_ACL_UNSAFE,
                        CreateMode.EPHEMERAL_SEQUENTIAL);
                if (list.size() + 1 == size) {
                    System.out.println("set data node size" + list.size());
                    zk.setData(root, String.valueOf(list.size() + 1).getBytes(), -1);
                }
                System.out.println(Thread.currentThread().getName() + ": " + name + " enter barrier!");
                return true;
            } else {
                //否则不进入
                System.out.println(Thread.currentThread().getName() + ": " + name + " barrier full, inaccessible!");
                return false;
            }
        }
    }

    /**
     * Wait until all reach barrier
     *
     * @return
     * @throws KeeperException
     * @throws InterruptedException
     */

    boolean leave() throws KeeperException, InterruptedException, UnsupportedEncodingException {
        while (true) {
            int data = Integer.parseInt(new String(zk.getData(root, false, new Stat()), "UTF-8"));
            if (data == size) {
                System.out.println("leave size: " + data);
                //离开
                zk.delete(name, -1);
                System.out.println(Thread.currentThread().getName() + ": " + name + " left barrier!");
                return true;
            } else {
                System.out.println(Thread.currentThread().getName() + ": " + name + " waitting for others!");
                Thread.sleep(1000);//每秒检查一次
            }
        }
    }

    public static void main(String[] args) {
        for (int i = 0; i < 3; i++) {
            new Thread(() -> {
                SyncPrimitiveBarrier syncPrimitiveBarrier = new SyncPrimitiveBarrier("localhost:2181", "/barrier_test", 3);
                boolean flag = false;
                try {
                    //模拟需要到达barrier的时间
                    Thread.sleep(ThreadLocalRandom.current().nextInt(1,5)*1000);
                    flag = syncPrimitiveBarrier.enter();

                    //尝试离开barrier
                    syncPrimitiveBarrier.leave();
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }
            }).start();

        }
    }
}

zookeeper 消息队列：

SyncPrimitiveQueue

produce(int i)：生成消息放入队列

consume()：消费队列消息

package org.windwant.zookeeper;

import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.data.Stat;

import java.nio.ByteBuffer;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Producer-Consumer queue
 */
public class SyncPrimitiveQueue extends SyncPrimitive {

    private String root;
    private int queueSize;

    /**
     * Constructor of producer-consumer queue
     *
     * @param domain
     * @param name
     */

    SyncPrimitiveQueue(String domain, String name, Integer queueSize) {
        super(queueSize);
        this.root = name;
        this.queueSize = queueSize;
        initZK(domain);
        initZKRootNode(root);
    }

    /**
     * Add element to the queue.
     *
     * @param i
     * @return
     */

    public boolean produce(int i) throws KeeperException, InterruptedException{
        synchronized (mutex) {
            List<String> children = zk.getChildren(root, false);
            if(children != null && children.size()>=mutex){
                System.out.println(Thread.currentThread().getName() + ": producer queue full, waiting for consuming");
                mutex.wait();
            }
            ByteBuffer b = ByteBuffer.allocate(4);
            byte[] value;

            b.putInt(i);
            value = b.array();
            String node = zk.create(root + "/element", value, Ids.OPEN_ACL_UNSAFE,
                    CreateMode.PERSISTENT_SEQUENTIAL);
            System.out.println(Thread.currentThread().getName() + ": produce value: " + node);
            mutex.notifyAll();//通知消费
            return true;
        }
    }


    /**
     * Remove first element from the queue.
     *
     * @return
     * @throws KeeperException
     * @throws InterruptedException
     */
    int consume() throws KeeperException, InterruptedException{
        int retvalue = -1;
        Stat stat = null;

        // Get the first element available
        while (true) {
            synchronized (mutex) {
                List<String> list = zk.getChildren(root, true);
                if (list.size() == 0) {
                    System.out.println(Thread.currentThread().getName() + ": resource not awailable, waitting for produce!");
                    mutex.wait();
                } else {
                    list.sort((String s1, String s2) -> s1.compareTo(s2)); //消费序号最小的节点
                    String dest = list.get(0);
                    System.out.println(Thread.currentThread().getName() + ": cosume value: " + root + "/" + dest);
                    byte[] b = zk.getData(root + "/" + dest,
                            false, stat);
                    zk.delete(root + "/" + dest, 0); //消费后删除
                    ByteBuffer buffer = ByteBuffer.wrap(b);
                    retvalue = buffer.getInt();
                    mutex.notifyAll();
                    return retvalue;
                }
            }
        }
    }

    public static void main(String[] args) {
        SyncPrimitiveQueue syncPrimitiveQueue = new SyncPrimitiveQueue("localhost:2181", "/queue_test", 10);
        //生产 每隔三秒 模拟慢生产
        new Thread(() -> {
            for (int i = 0; i < Integer.MAX_VALUE; i++) {
                try {
                    syncPrimitiveQueue.produce(i);
                    Thread.sleep(ThreadLocalRandom.current().nextInt(0, 3)*1000);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        try {
            Thread.sleep(10000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        //消费 每隔一秒 模拟快消费
        new Thread(() -> {
            for (int i = 0; i < Integer.MAX_VALUE ; i++) {
                try {
                    syncPrimitiveQueue.consume();
                    Thread.sleep(ThreadLocalRandom.current().nextInt(0, 3)*1000);
                } catch (KeeperException e) {
                    e.printStackTrace();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}

zookeeper分布式锁：

SynZookeeperLock

getInstance(String domain)：获取zookeeper实例

tryLock(String domain, String path, byte[] data, CountDownLatch c)：尝试获取分布式锁。

package org.windwant.zookeeper;

import org.apache.zookeeper.*;
import org.apache.zookeeper.ZooDefs.Ids;

import java.io.IOException;
import java.util.concurrent.*;

/**
 * zookeeper 分布式锁
 */
public class SynZookeeperLock {
    private static final int SESSION_TIMEOUT = 30000;

    public static ZooKeeper getInstance(String domain){
        try {
            CountDownLatch c = new CountDownLatch(1);
            ZooKeeper zk = new ZooKeeper(domain, SESSION_TIMEOUT, new Watcher() {
                @Override
                public void process(WatchedEvent event) {
                    if (event.getState() == Watcher.Event.KeeperState.SyncConnected) {
                        c.countDown(); // 唤醒当前正在执行的线程
                    }
                }
            });
            //阻塞直到连接完成
            c.await();
            return zk;
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        return null;
    }
    /**
     * 获取分布式锁
     * 使用临时节点，避免进程获取锁后，down掉未释放锁问题
     * @param domain
     * @param path
     * @param data
     * @param c
     */
    public static void tryLock(String domain, String path, byte[] data, CountDownLatch c){
        //每次获取锁使用新的会话连接
        ZooKeeper zk = getInstance(domain);
        zk.create(path, data, Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL, (rc, path1, ctx, name) -> {
            //节点创建成功，获取锁
            if (rc == 0) {
                System.out.println(Thread.currentThread().getName() + "：result " + rc + " lock " + path + ", created!");
                try {
                    //模拟获取锁后3秒释放
                    Thread.sleep(3000);
                    System.out.println(Thread.currentThread().getName() + "：task complete，try release lock！");
                    zk.delete(path, -1, (rc1, path2, ctx1) -> {
                        if(rc1 == 0){
                            System.out.println(Thread.currentThread().getName() + "：lock released！");
                        }
                    }, null);

                } catch (InterruptedException e) {
                    e.printStackTrace();
                }finally {
                    //释放等待
                    c.countDown();
                }
            } else if(rc == -110) {//节点已存在，则说明锁已被其它进程获取，则创建watch，并阻塞等待
                System.out.println(Thread.currentThread().getName() + "：result " + rc + " lock " + path + " already created, waiting!");
                try {
                    zk.exists(path, event -> {
                        //watch 到锁删除事件，则触发重新获取锁
                        if (event.getType().equals(Watcher.Event.EventType.NodeDeleted)) {
                            System.out.println(Thread.currentThread().getName() + "：get node deleted event! try lock!");
                            //释放连接，避免服务器因为连接数限制
                            try {
                                zk.close();
                            } catch (InterruptedException e) {
                                e.printStackTrace();
                            }
                            SynZookeeperLock.tryLock(domain, path, data, c);
                            c.countDown();
                        }
                    });
                } catch (KeeperException e) {
                    //包括ConnectionLossException（网络，服务器故障） 需要确认客户端重连执行情况 之前的请求是否需要重新执行
                    e.printStackTrace();
                    c.countDown();
                } catch (InterruptedException e) {
                    //线程中断，打断请求
                    e.printStackTrace();
                    c.countDown();
                }
            }else {
                //-4 -112
                System.out.println(Thread.currentThread().getName() + ": connection lose or session invalid");
                c.countDown();
//                tryLock(domain, path, data, c);
            }
        }, new Object());
        try {
            //阻塞等待结果
            c.await();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            c.countDown();
        }
    }

    public static void main(String[] args) {
        String lockPath = "/testlock";
        byte[] lock = "lock".getBytes();
        String domain = "127.0.0.1:2181";
        //测试获取锁线程 注意服务器最大连接数限制
        for (int i = 0; i < 20; i++) {
            Thread tmp = new Thread( () -> tryLock(domain, lockPath, lock, new CountDownLatch(1)));
            tmp.start();
        }
    }
}

项目地址：https://github.com/windwant/windwant-demo/tree/master/zookeeper-service