分布式系统中经常需要协调多进程,多个jvm,或者多台机器之间的同步问题,得益于zookeeper,实现了一个分布式的共享锁,方便在多台服务器之间竞争资源时,来协调各系统之间的协作和同步。
package com.zookeeper.lock.server; 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; /** DistributedLock lock = null; try { lock = new DistributedLock("127.0.0.1:2182","test"); lock.lock(); //do something... } catch (Exception e) { e.printStackTrace(); } finally { if(lock != null) lock.unlock(); } * @author xueliang * */ 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.zookeeper.lock.client; 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; /** ConcurrentTask[] task = new ConcurrentTask[5]; for(int i=0;i<task.length;i++){ task[i] = new ConcurrentTask(){ public void run() { System.out.println("=============="); }}; } new ConcurrentTest(task); * @author xueliang * */ public class ConcurrentClient { 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 ConcurrentClient(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.zookeeper.lock.test; import com.zookeeper.lock.client.ConcurrentClient; import com.zookeeper.lock.client.ConcurrentClient.ConcurrentTask; import com.zookeeper.lock.server.DistributedLock; public class Test { public static void main(String[] args) { Runnable task1 = new Runnable(){ public void run() { DistributedLock lock = null; try { lock = new DistributedLock("127.0.0.1:2182","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[5]; 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 ConcurrentClient(tasks); } }
测试结果:
/locks/test1_lock_0000004356 is created /locks/test1_lock_0000004356==test1_lock_0000004356 Thread 8 /locks/test1_lock_0000004356 get lock true /locks/test2_lock_0000004357 is created /locks/test2_lock_0000004359 is created /locks/test2_lock_0000004358 is created /locks/test2_lock_0000004363 is created /locks/test2_lock_0000004361 is created /locks/test2_lock_0000004360 is created /locks/test2_lock_0000004362 is created /locks/test2_lock_0000004366 is created /locks/test2_lock_0000004365 is created /locks/test2_lock_0000004364 is created /locks/test2_lock_0000004357==test2_lock_0000004357 Thread 14 /locks/test2_lock_0000004357 get lock true Thread 14 running unlock /locks/test2_lock_0000004357 /locks/test2_lock_0000004358==test2_lock_0000004357 /locks/test2_lock_0000004361==test2_lock_0000004357 /locks/test2_lock_0000004359==test2_lock_0000004357 /locks/test2_lock_0000004362==test2_lock_0000004357 Thread 12 waiting for /locks/test2_lock_0000004360 /locks/test2_lock_0000004366==test2_lock_0000004357 Thread 18 waiting for /locks/test2_lock_0000004357 /locks/test2_lock_0000004363==test2_lock_0000004357 Thread 18 running unlock /locks/test2_lock_0000004358 Thread 13 waiting for /locks/test2_lock_0000004362 /locks/test2_lock_0000004365==test2_lock_0000004358 Thread 16 waiting for /locks/test2_lock_0000004361 Thread 19 waiting for /locks/test2_lock_0000004358 /locks/test2_lock_0000004360==test2_lock_0000004358 Thread 15 waiting for /locks/test2_lock_0000004365 /locks/test2_lock_0000004364==test2_lock_0000004358 Thread 11 waiting for /locks/test2_lock_0000004364 Thread 20 waiting for /locks/test2_lock_0000004359 Thread 19 running unlock /locks/test2_lock_0000004359 Thread 17 waiting for /locks/test2_lock_0000004363 Thread 20 running unlock /locks/test2_lock_0000004360 Thread 12 running unlock /locks/test2_lock_0000004361 Thread 16 running unlock /locks/test2_lock_0000004362 Thread 13 running unlock /locks/test2_lock_0000004363 Thread 17 running unlock /locks/test2_lock_0000004364 Thread 11 running unlock /locks/test2_lock_0000004365 Thread 15 running unlock /locks/test2_lock_0000004366 min: 506 max: 1481 avg: 968 err: 0 ===Thread 8 running unlock /locks/test1_lock_0000004356
关于zookeeper的很好的文章:
https://www.ibm.com/developerworks/cn/opensource/os-cn-zookeeper/
这个分布式共享锁就是参考这篇文章实现的。
来自:http://my.oschina.net/shenxueliang/blog/135865
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