Zookeeper lock

来源：互联网发布：矩阵式大灯编辑：程序博客网时间：2024/05/16 08:02
获得锁：1.创建根节点"/root"2.在根节点下新建子节点"/root/c-xxxxxx"，SEQUENTIAL模式3.对根节点调用getChildren()，如果第2步创建的节点是所有子节点中序号最小的，则获得锁；否则进入第4步4.在序号最小的子节点上调用exists()，当序号最小的子节点被删除后返回第3步释放锁：删除自己创建的子节点即可
package com.lock;/** * Created by bcm on 15-3-13. */import java.io.IOException;import java.net.InetAddress;import java.util.List;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.Ids;import org.apache.zookeeper.ZooKeeper;import org.apache.zookeeper.data.Stat;public class Locks implements Watcher{    static ZooKeeper zk=null;    static Integer mutex=null;    String name=null;    String path=null;    @Override    synchronized public void process(WatchedEvent event) {        System.out.println("process:"+event.toString());        synchronized(mutex){            mutex.notify();        }    }    Locks(String address){        try{            zk=new ZooKeeper(address,30000000,this);//            zk.create("/lock", new byte[0], Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);            mutex=new Integer(-1);            name = new String(InetAddress.getLocalHost().getCanonicalHostName().toString());        }catch(IOException e){            zk=null;        }//        catch (KeeperException e) {//            e.printStackTrace();//        } catch (InterruptedException e) {//            e.printStackTrace();//        }    }    private String  minSeq(List<String> list){        int min=Integer.parseInt(list.get(0).substring(11));        String minString ="";        minString =  list.get(0).substring(11);        for(int i=1;i<list.size();i++){            if(min>Integer.parseInt(list.get(i).substring(11))){                min=Integer.parseInt(list.get(i).substring(11));                minString = list.get(i).substring(11);            }        }        return minString;    }    boolean getLock() throws KeeperException, InterruptedException{        //create方法返回新建的节点的完整路径        path=zk.create("/lock/"+name+"-", new byte[0], Ids.OPEN_ACL_UNSAFE,CreateMode.PERSISTENT_SEQUENTIAL);        String minStr;        while(true){            synchronized(mutex){                List<String> list=zk.getChildren("/lock", true);                minStr=minSeq(list);                //如果刚建的节点是根节点的所有子节点中序号最小的，则获得了锁，可以返回true                if(Integer.parseInt(minStr)==Integer.parseInt(path.substring(17))){                    return true;                }else{                    mutex.wait();       //等待事件（新建节点或删除节点）发生                    while(true){                       zk.getChildren("/lock", true); //必须再注册watcher，以便监听znode节点。                        Stat s=zk.exists("/lock/"+name+"-"+minStr, true);      //查看序号最小的子节点还在不在                        if(s!=null)     //如果还在，则继续等待事件发生                            mutex.wait();                        else            //如果不在，则跳外层循环中，查看新的最小序号的子节点是谁                            break;                    }                }            }        }    }    boolean releaseLock() throws KeeperException, InterruptedException{        if(path!=null){            zk.delete(path, -1);            path=null;        }        return true;    }    public static void main(String []args) throws KeeperException, InterruptedException{        Locks lock1=new Locks("localhost:2181");        if(lock1.getLock()){            System.out.println("T1 Get lock at "+System.currentTimeMillis());            for(int i=0;i<1000;++i)                Thread.sleep(5000);            lock1.releaseLock();        }        Locks lock2=new Locks("localhost:2181");        if(lock2.getLock()){            System.out.println("T2 Get lock at "+System.currentTimeMillis());            lock2.releaseLock();        }    }}
0 0