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package cn.ac.iie.utils.zookeeper;
import cn.ac.iie.common.FlowWriteConfig;
import cn.ac.iie.utils.system.SnowflakeId;
import org.apache.log4j.Logger;
import org.apache.zookeeper.*;
import org.apache.zookeeper.data.Stat;
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;
/**
* @author qidaijie
*/
public class DistributedLock implements Lock, Watcher {
private static Logger logger = Logger.getLogger(DistributedLock.class);
private ZooKeeper zk = null;
/**
* 根节点
*/
private final String ROOT_LOCK = "/locks";
/**
* 竞争的资源
*/
private String lockName;
/**
* 等待的前一个锁
*/
private String waitLock;
/**
* 当前锁
*/
private String currentLock;
/**
* 计数器
*/
private CountDownLatch countDownLatch;
private int sessionTimeout = 2000;
private List<Exception> exceptionList = new ArrayList<Exception>();
/**
* 配置分布式锁
*
* @param config 连接的url
* @param lockName 竞争资源
*/
public DistributedLock(String config, String lockName) {
this.lockName = lockName;
try {
// 连接zookeeper
zk = new ZooKeeper(config, sessionTimeout, this);
Stat stat = zk.exists(ROOT_LOCK, false);
if (stat == null) {
// 如果根节点不存在，则创建根节点
zk.create(ROOT_LOCK, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
}
} catch (IOException | InterruptedException | KeeperException e) {
logger.error("Node already exists!");
}
}
// 节点监视器
@Override
public void process(WatchedEvent event) {
if (this.countDownLatch != null) {
this.countDownLatch.countDown();
}
}
@Override
public void lock() {
if (exceptionList.size() > 0) {
throw new LockException(exceptionList.get(0));
}
try {
if (this.tryLock()) {
System.out.println(Thread.currentThread().getName() + " " + lockName + "获得了锁");
} else {
// 等待锁
waitForLock(waitLock, sessionTimeout);
}
} catch (InterruptedException | KeeperException e) {
e.printStackTrace();
}
}
@Override
public boolean tryLock() {
try {
String splitStr = "_lock_";
if (lockName.contains(splitStr)) {
throw new LockException("锁名有误");
}
// 创建临时有序节点
currentLock = zk.create(ROOT_LOCK + "/" + lockName + splitStr, new byte[0],
ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
// 取所有子节点
List<String> subNodes = zk.getChildren(ROOT_LOCK, false);
// 取出所有lockName的锁
List<String> lockObjects = new ArrayList<String>();
for (String node : subNodes) {
String tmpNode = node.split(splitStr)[0];
if (tmpNode.equals(lockName)) {
lockObjects.add(node);
}
}
Collections.sort(lockObjects);
// 若当前节点为最小节点，则获取锁成功
if (currentLock.equals(ROOT_LOCK + "/" + lockObjects.get(0))) {
return true;
}
// 若不是最小节点，则找到自己的前一个节点
String prevNode = currentLock.substring(currentLock.lastIndexOf("/") + 1);
waitLock = lockObjects.get(Collections.binarySearch(lockObjects, prevNode) - 1);
} catch (InterruptedException | KeeperException e) {
e.printStackTrace();
}
return false;
}
@Override
public boolean tryLock(long timeout, TimeUnit unit) {
try {
if (this.tryLock()) {
return true;
}
return waitForLock(waitLock, timeout);
} catch (Exception e) {
e.printStackTrace();
}
return false;
}
// 等待锁
private boolean waitForLock(String prev, long waitTime) throws KeeperException, InterruptedException {
Stat stat = zk.exists(ROOT_LOCK + "/" + prev, true);
if (stat != null) {
this.countDownLatch = new CountDownLatch(1);
// 计数等待，若等到前一个节点消失，则precess中进行countDown，停止等待，获取锁
this.countDownLatch.await(waitTime, TimeUnit.MILLISECONDS);
this.countDownLatch = null;
}
return true;
}
@Override
public void unlock() {
try {
zk.delete(currentLock, -1);
currentLock = null;
zk.close();
} catch (InterruptedException | KeeperException e) {
e.printStackTrace();
}
}
@Override
public Condition newCondition() {
return null;
}
@Override
public void lockInterruptibly() throws InterruptedException {
this.lock();
}
public class LockException extends RuntimeException {
private static final long serialVersionUID = 1L;
public LockException(String e) {
super(e);
}
public LockException(Exception e) {
super(e);
}
}
public static void main(String[] args) {
ZookeeperUtils zookeeperUtils = new ZookeeperUtils();
Runnable runnable = new Runnable() {
@Override
public void run() {
DistributedLock lock = null;
try {
// lock = new DistributedLock(FlowWriteConfig.ZOOKEEPER_SERVERS, "disLocks1");
// lock.lock();
System.out.println(SnowflakeId.generateId());
} finally {
if (lock != null) {
lock.unlock();
}
}
}
};
for (int i = 0; i < 10; i++) {
Thread t = new Thread(runnable);
t.start();
}
}
}
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