zookeeper 实现分布式锁

package com.concurrent;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
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;

public class DistributedLock implements Lock, Watcher {
    private ZooKeeper zk;
    private String root = "/locks";// 根
    private String lockName;// 竞争资源的标志
    private String waitNode;// 等待前一个锁
    private String myZnode;// 当前锁
    private CountDownLatch latch;// 计数器
    private int sessionTimeout = 30000;
    private List<Exception> exception = new ArrayList<Exception>();

    /**
     * 创建分布式锁,使用前请确认config配置的zookeeper服务可用
     * 
     * @param config
     *            127.0.0.1:2181
     * @param lockName
     *            竞争资源标志,lockName中不能包含单词lock
     */
    public DistributedLock(String config, String lockName) {
        this.lockName = lockName;
        // 创建一个与服务器的连接
        try {
            zk = new ZooKeeper(config, sessionTimeout, this);
            Stat stat = zk.exists(root, false);
            if (stat == null) {
                // 创建根节点
                zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
            }
        } catch (IOException e) {
            exception.add(e);
        } catch (KeeperException e) {
            exception.add(e);
        } catch (InterruptedException e) {
            exception.add(e);
        }
    }

    /**
     * zookeeper节点的监视器
     */
    public void process(WatchedEvent event) {
        if (this.latch != null) {
            this.latch.countDown();
        }
    }

    public void lock() {
        if (exception.size() > 0) {
            throw new LockException(exception.get(0));
        }
        try {
            if (this.tryLock()) {
                System.out.println("Thread " + Thread.currentThread().getId() + " " + myZnode + " get lock true");
                return;
            } else {
                waitForLock(waitNode, sessionTimeout);// 等待锁
            }
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
    }

    public boolean tryLock() {
        try {
            String splitStr = "_lock_";
            if (lockName.contains(splitStr))
                throw new LockException("lockName can not contains \\u000B");
            // 创建临时子节点
            myZnode = zk.create(root + "/" + lockName + splitStr, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
            System.out.println(myZnode + " is created ");
            // 取出所有子节点
            List<String> subNodes = zk.getChildren(root, false);
            // 取出所有lockName的锁
            List<String> lockObjNodes = new ArrayList<String>();
            for (String node : subNodes) {
                String _node = node.split(splitStr)[0];
                if (_node.equals(lockName)) {
                    lockObjNodes.add(node);
                }
            }
            Collections.sort(lockObjNodes);
            System.out.println(myZnode + "==" + lockObjNodes.get(0));
            if (myZnode.equals(root + "/" + lockObjNodes.get(0))) {
                // 如果是最小的节点,则表示取得锁
                return true;
            }
            // 如果不是最小的节点，找到比自己小1的节点
            String subMyZnode = myZnode.substring(myZnode.lastIndexOf("/") + 1);
            waitNode = lockObjNodes.get(Collections.binarySearch(lockObjNodes, subMyZnode) - 1);
        } catch (KeeperException e) {
            throw new LockException(e);
        } catch (InterruptedException e) {
            throw new LockException(e);
        }
        return false;
    }

    public boolean tryLock(long time, TimeUnit unit) {
        try {
            if (this.tryLock()) {
                return true;
            }
            return waitForLock(waitNode, time);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }

    private boolean waitForLock(String lower, long waitTime) throws InterruptedException, KeeperException {
        Stat stat = zk.exists(root + "/" + lower, true);
        // 判断比自己小一个数的节点是否存在,如果不存在则无需等待锁,同时注册监听
        if (stat != null) {
            System.out.println("Thread " + Thread.currentThread().getId() + " waiting for " + root + "/" + lower);
            this.latch = new CountDownLatch(1);
            this.latch.await(waitTime, TimeUnit.MILLISECONDS);
            this.latch = null;
        }
        return true;
    }

    public void unlock() {
        try {
            System.out.println("unlock " + myZnode);
            zk.delete(myZnode, -1);
            myZnode = null;
            zk.close();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } catch (KeeperException e) {
            e.printStackTrace();
        }
    }

    public void lockInterruptibly() throws InterruptedException {
        this.lock();
    }

    public Condition newCondition() {
        return null;
    }

    public class LockException extends RuntimeException {
        private static final long serialVersionUID = 1L;

        public LockException(String e) {
            super(e);
        }

        public LockException(Exception e) {
            super(e);
        }
    }
}

package com.concurrent;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;

public class ConcurrentTest {
    private CountDownLatch startSignal = new CountDownLatch(1);// 开始阀门
    private CountDownLatch doneSignal = null;// 结束阀门
    private CopyOnWriteArrayList<Long> list = new CopyOnWriteArrayList<Long>();
    private AtomicInteger err = new AtomicInteger();// 原子递增
    private ConcurrentTask[] task = null;

    public ConcurrentTest(ConcurrentTask... task) {
        this.task = task;
        if (task == null) {
            System.out.println("task can not null");
            System.exit(1);
        }
        doneSignal = new CountDownLatch(task.length);
        start();
    }

    /**
     * @param args
     * @throws ClassNotFoundException
     */
    private void start() {
        // 创建线程，并将所有线程等待在阀门处
        createThread();
        // 打开阀门
        startSignal.countDown();// 递减锁存器的计数，如果计数到达零，则释放所有等待的线程
        try {
            doneSignal.await();// 等待所有线程都执行完毕
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        // 计算执行时间
        getExeTime();
    }

    /**
     * 初始化所有线程，并在阀门处等待
     */
    private void createThread() {
        long len = doneSignal.getCount();
        for (int i = 0; i < len; i++) {
            final int j = i;
            new Thread(new Runnable() {
                public void run() {
                    try {
                        startSignal.await();// 使当前线程在锁存器倒计数至零之前一直等待
                        long start = System.currentTimeMillis();
                        task[j].run();
                        long end = (System.currentTimeMillis() - start);
                        list.add(end);
                    } catch (Exception e) {
                        err.getAndIncrement();// 相当于err++
                    }
                    doneSignal.countDown();
                }
            }).start();
        }
    }

    /**
     * 计算平均响应时间
     */
    private void getExeTime() {
        int size = list.size();
        List<Long> _list = new ArrayList<Long>(size);
        _list.addAll(list);
        Collections.sort(_list);
        long min = _list.get(0);
        long max = _list.get(size - 1);
        long sum = 0L;
        for (Long t : _list) {
            sum += t;
        }
        long avg = sum / size;
        System.out.println("min: " + min);
        System.out.println("max: " + max);
        System.out.println("avg: " + avg);
        System.out.println("err: " + err.get());
    }

    public interface ConcurrentTask {
        void run();
    }
}

package com.concurrent;

import com.concurrent.ConcurrentTest.ConcurrentTask;

public class ZkTest {
    public static void main(String[] args) {
        Runnable task1 = new Runnable() {
            public void run() {
                DistributedLock lock = null;
                try {
                    lock = new DistributedLock("127.0.0.1:2181", "test1");
                    // lock = new DistributedLock("127.0.0.1:2182","test2");
                    lock.lock();
                    Thread.sleep(3000);
                    System.out.println("===Thread " + Thread.currentThread().getId() + " running");
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (lock != null)
                        lock.unlock();
                }

            }

        };
        new Thread(task1).start();
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e1) {
            e1.printStackTrace();
        }
        ConcurrentTask[] tasks = new ConcurrentTask[6];
        for (int i = 0; i < tasks.length; i++) {
            ConcurrentTask task3 = new ConcurrentTask() {
                public void run() {
                    DistributedLock lock = null;
                    try {
                        lock = new DistributedLock("127.0.0.1:2181", "test2");
                        lock.lock();
                        System.out.println("Thread " + Thread.currentThread().getId() + " running");
                    } catch (Exception e) {
                        e.printStackTrace();
                    } finally {
                        lock.unlock();
                    }

                }
            };
            tasks[i] = task3;
        }
        new ConcurrentTest(tasks);
    }
}