实现互斥锁

package com.zookeeper.lock;import java.util.Collections;import java.util.Comparator;import java.util.List;import java.util.concurrent.CountDownLatch;import java.util.concurrent.TimeUnit;import org.I0Itec.zkclient.IZkDataListener;import org.I0Itec.zkclient.ZkClient;import org.I0Itec.zkclient.exception.ZkNoNodeException;public class BaseDistributedLock {    private final ZkClient client;    private final String path;    // zookeeper中locker节点的路径    private final String basePath;    private final String lockName;    private static final Integer MAX_RETRY_COUNT = 10;    public BaseDistributedLock(ZkClient client, String path, String lockName) {        this.client = client;        this.basePath = path;        this.path = path.concat("/").concat(lockName);        this.lockName = lockName;    }    private void deleteOurPath(String ourPath) throws Exception {        client.delete(ourPath);    }    private String createLockNode(ZkClient client, String path)            throws Exception {        return client.createEphemeralSequential(path, null);    }    private boolean waitToLock(long startMillis, Long millisToWait,            String ourPath) throws Exception {        boolean haveTheLock = false;        boolean doDelete = false;        try {            while (!haveTheLock) {                // 获取lock节点下的所有节点                List children = getSortedChildren();                String sequenceNodeName = ourPath                        .substring(basePath.length() + 1);                // 获取当前节点的在所有节点列表中的位置                int ourIndex = children.indexOf(sequenceNodeName);                // 节点位置小于0,说明没有找到节点                if (ourIndex < 0) {                    throw new ZkNoNodeException("节点没有找到: " + sequenceNodeName);                }                // 节点位置大于0说明还有其他节点在当前的节点前面，就需要等待其他的节点都释放                boolean isGetTheLock = ourIndex == 0;                String pathToWatch = (String) (isGetTheLock ? null : children                        .get(ourIndex - 1));                if (isGetTheLock) {                    haveTheLock = true;                } else {                    String previousSequencePath = basePath.concat("/").concat(                            pathToWatch);                    final CountDownLatch latch = new CountDownLatch(1);                    final IZkDataListener previousListener = new IZkDataListener() {                        public void handleDataDeleted(String dataPath)                                throws Exception {                            latch.countDown();                        }                        public void handleDataChange(String dataPath,                                Object data) throws Exception {                            // ignore                        }                    };                    try {                        // 如果节点不存在会出现异常                        client.subscribeDataChanges(previousSequencePath,                                previousListener);                        if (millisToWait != null) {                            millisToWait -= (System.currentTimeMillis() - startMillis);                            startMillis = System.currentTimeMillis();                            if (millisToWait <= 0) {                                doDelete = true; // timed out - delete our node                                break;                            }                            latch.await(millisToWait, TimeUnit.MICROSECONDS);                        } else {                            latch.await();                        }                    } catch (ZkNoNodeException e) {                        // ignore                    } finally {                        client.unsubscribeDataChanges(previousSequencePath,                                previousListener);                    }                }            }        } catch (Exception e) {            // 发生异常需要删除节点            doDelete = true;            throw e;        } finally {            // 如果需要删除节点            if (doDelete) {                deleteOurPath(ourPath);            }        }        return haveTheLock;    }    private String getLockNodeNumber(String str, String lockName) {        int index = str.lastIndexOf(lockName);        if (index >= 0) {            index += lockName.length();            return index <= str.length() ? str.substring(index) : "";        }        return str;    }    List
      
        getSortedChildren() throws Exception {        try {            List
       
         children = client.getChildren(basePath);            Collections.sort(children, new Comparator
        
         () {                public int compare(String lhs, String rhs) {                    return getLockNodeNumber(lhs, lockName).compareTo(                            getLockNodeNumber(rhs, lockName));                }            });            return children;        } catch (ZkNoNodeException e) {            client.createPersistent(basePath, true);            return getSortedChildren();        }    }    protected void releaseLock(String lockPath) throws Exception {        deleteOurPath(lockPath);    }    protected String attemptLock(long time, TimeUnit unit) throws Exception {        final long startMillis = System.currentTimeMillis();        final Long millisToWait = (unit != null) ? unit.toMillis(time) : null;        String ourPath = null;        boolean hasTheLock = false;        boolean isDone = false;        int retryCount = 0;        // 网络闪断需要重试一试        while (!isDone) {            isDone = true;            try {                ourPath = createLockNode(client, path);                hasTheLock = waitToLock(startMillis, millisToWait, ourPath);            } catch (ZkNoNodeException e) {                if (retryCount++ < MAX_RETRY_COUNT) {                    isDone = false;                } else {                    throw e;                }            }        }        if (hasTheLock) {            return ourPath;        }        return null;    }}
        
       
      

接口类

package com.zookeeper.lock;import java.util.concurrent.TimeUnit;public interface DistributedLock {    /** 获取锁，如果没有得到就等待 */    public void acquire() throws Exception;    /**     * 获取锁，直到超时     *      * @param time     *            超时时间     * @param unit     *            参数的单位     * @return 是否获取到锁     * @throws Exception     */    public boolean acquire(long time, TimeUnit unit) throws Exception;    /**     * 释放锁     *      * @throws Exception     */    public void release() throws Exception;}

测试类

package com.zookeeper.lock;import org.I0Itec.zkclient.ZkClient;import org.I0Itec.zkclient.serialize.BytesPushThroughSerializer;import coom.zookeeperdemo.lock.SimpleDistributedLockMutex;public class TestDistributedLock {    public static void main(String[] args) {        final ZkClient zkClientExt1 = new ZkClient("192.168.1.105:2181",                5000, 5000, new BytesPushThroughSerializer());        final SimpleDistributedLockMutex mutex1 = new SimpleDistributedLockMutex(                zkClientExt1, "/Mutex");        final ZkClient zkClientExt2 = new ZkClient("192.168.1.105:2181",                5000, 5000, new BytesPushThroughSerializer());        final SimpleDistributedLockMutex mutex2 = new SimpleDistributedLockMutex(                zkClientExt2, "/Mutex");        try {            mutex1.acquire();            System.out.println("Client1 locked");            Thread client2Thd = new Thread(new Runnable() {                public void run() {                    try {                        mutex2.acquire();                        System.out.println("Client2 locked");                        mutex2.release();                        System.out.println("Client2 released lock");                    } catch (Exception e) {                        e.printStackTrace();                    }                }            });            client2Thd.start();            Thread.sleep(5000);            mutex1.release();            System.out.println("Client1 released lock");            client2Thd.join();        } catch (Exception e) {            e.printStackTrace();        }    }}

 

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