zkDistributedLock

package cn.wpeace.zktest; 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.Watcher.Event.KeeperState; import org.apache.zookeeper.data.Stat; /** * @author peace * */ 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 CountDownLatch connectedSignal=new CountDownLatch(1); private int sessionTimeout = 30000; /** * 创建分布式锁,使用前请确认config配置的zookeeper服务可用 * @param config 192.168.1.127:2181 * @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); connectedSignal.await(); Stat stat = zk.exists(root, false);//此去不执行 Watcher if(stat == null){ // 创建根节点 zk.create(root, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT); } } catch (IOException e) { throw new LockException(e); } catch (KeeperException e) { throw new LockException(e); } catch (InterruptedException e) { throw new LockException(e); } } /** * zookeeper节点的监视器 */ public void process(WatchedEvent event) { //建立连接用 if(event.getState()==KeeperState.SyncConnected){ connectedSignal.countDown(); return; } //其他线程放弃锁的标志 if(this.latch != null) { this.latch.countDown(); } } public void lock() { 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); if(myZnode.equals(root+"/"+lockObjNodes.get(0))){ //如果是最小的节点,则表示取得锁 System.out.println(myZnode + "==" + lockObjNodes.get(0)); 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);//找到前一个子节点 } 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);//同时注册监听。 //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);//等待，这里应该一直等待其他线程释放锁 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); } } }