zookeeper锁原理(如何实现分布式锁)

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zookeeper分布式锁的使用会涉及到分布式事物
因此封装有@Transactional的方法如下：

@Override
    public BizReturn<String> insertMagicCubeVehicles(MagicCubeVehicleSaveRequest request) throws BizException { 
   
        ZooKeeperSession zkSession = ZooKeeperSession.getInstance();
        zkSession.acquireDistributedLock("/magicCube-lock-"+request.getVehicleNumber());
        try{ 
   
            BizReturn<String> bizReturn = insertMagicCubeVehicle(request);
            return bizReturn;
        }finally { 
   
            // 释放分布式锁
            zkSession.releaseDistributedLock("/magicCube-lock-"+request.getVehicleNumber());
        }
    }

封装的方法：

insertMagicCubeVehicle(request);

ZooKeeperSession的工具类：

package tf56.magiccube.util.zookeeper;
import java.util.concurrent.CountDownLatch;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.WatchedEvent;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.Watcher.Event.KeeperState;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.Stat;
/** * ZooKeeperSession * @author Administrator * */
public class ZooKeeperSession { 

private static CountDownLatch connectedSemaphore = new CountDownLatch(1);
private ZooKeeper zookeeper;
public ZooKeeperSession() { 

// 去连接zookeeper server，创建会话的时候，是异步去进行的
// 所以要给一个监听器，说告诉我们什么时候才是真正完成了跟zk server的连接
try { 

this.zookeeper = new ZooKeeper(
"mt-zookeeper-vip:2181",
50000,
new ZooKeeperWatcher());
// 给一个状态CONNECTING，连接中
System.out.println(zookeeper.getState());
try { 

// CountDownLatch
// java多线程并发同步的一个工具类
// 会传递进去一些数字，比如说1,2 ，3 都可以
// 然后await()，如果数字不是0，那么久卡住，等待
// 其他的线程可以调用coutnDown()，减1
// 如果数字减到0，那么之前所有在await的线程，都会逃出阻塞的状态
// 继续向下运行
connectedSemaphore.await();
} catch(InterruptedException e) { 

e.printStackTrace();
}
System.out.println("ZooKeeper session established......");
} catch (Exception e) { 

e.printStackTrace();
}
}
/** * 获取分布式锁 * @param productId */
public void acquireDistributedLock(Long productId) { 

String path = "/product-lock-" + productId;
try { 

zookeeper.create(path, "".getBytes(),
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println("success to acquire lock for product[id=" + productId + "]");
} catch (Exception e) { 

// 如果那个车辆对应的锁的node，已经存在了，就是已经被别人加锁了，那么就这里就会报错
// NodeExistsException
int count = 0;
while(true) { 

try { 

Thread.sleep(1000);
zookeeper.create(path, "".getBytes(),
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
} catch (Exception e2) { 

count++;
System.out.println("the " + count + " times try to acquire lock for product[id=" + productId + "]......");
continue;
}
System.out.println("success to acquire lock for product[id=" + productId + "] after " + count + " times try......");
break;
}
}
}
/** * 获取分布式锁 * @param path */
public void acquireDistributedLock(String path) { 

try { 

zookeeper.create(path, "".getBytes(),
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println("success to acquire lock for " + path);
} catch (Exception e) { 

// 如果那个车辆对应的锁的node，已经存在了，就是已经被别人加锁了，那么就这里就会报错
// NodeExistsException
int count = 0;
while(true) { 

try { 

Thread.sleep(1000);
zookeeper.create(path, "".getBytes(),
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
} catch (Exception e2) { 

count++;
System.out.println("the " + count + " times try to acquire lock for " + path + "......");
continue;
}
System.out.println("success to acquire lock for " + path + " after " + count + " times try......");
break;
}
}
}
/** * 获取分布式锁 * @param path */
public boolean acquireFastFailedDistributedLock(String path) { 

try { 

zookeeper.create(path, "".getBytes(),
Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL);
System.out.println("success to acquire lock for " + path);
return true;
} catch (Exception e) { 

System.out.println("fail to acquire lock for " + path);
}
return false;
}
/** * 释放掉一个分布式锁 * @param productId */
public void releaseDistributedLock(Long productId) { 

String path = "/product-lock-" + productId;
try { 

zookeeper.delete(path, -1);
System.out.println("release the lock for product[id=" + productId + "]......");
} catch (Exception e) { 

e.printStackTrace();
}
}
/** * 释放掉一个分布式锁 * @param path */
public void releaseDistributedLock(String path) { 

try { 

zookeeper.delete(path, -1);
System.out.println("release the lock for " + path + "......");
} catch (Exception e) { 

e.printStackTrace();
}
}
public String getNodeData(String path) { 

try { 

return new String(zookeeper.getData(path, false, new Stat()));
} catch (Exception e) { 

e.printStackTrace();
}
return "";
}
public void setNodeData(String path, String data) { 

try { 

zookeeper.setData(path, data.getBytes(), -1);
} catch (Exception e) { 

e.printStackTrace();
}
}
public void createNode(String path) { 

try { 

zookeeper.create(path, "".getBytes(), Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
} catch (Exception e) { 

}
}
/** * 建立zk session的watcher * @author Administrator * */
private class ZooKeeperWatcher implements Watcher { 

public void process(WatchedEvent event) { 

System.out.println("Receive watched event: " + event.getState());
if(KeeperState.SyncConnected == event.getState()) { 

connectedSemaphore.countDown();
}
}
}
/** * 封装单例的静态内部类 * @author Administrator * */
private static class Singleton { 

private static ZooKeeperSession instance;
static { 

instance = new ZooKeeperSession();
}
public static ZooKeeperSession getInstance() { 

return instance;
}
}
/** * 获取单例 * @return */
public static ZooKeeperSession getInstance() { 

return Singleton.getInstance();
}
/** * 初始化单例的便捷方法 */
public static void init() { 

getInstance();
}
}