依赖Zookeeper生成全局唯一序列号

下面2张图来自：http://www.open-open.com/doc/view/2e0a82e0081d489dace301a2c512053c

关于Zookeeper服务安装，配置，启动, 客户端操作参见：
/article/4249738.html
/article/4249737.html

1.利用Zookeeper的znode数据版本生成序列号




利用zkClient封装包操作实现：

//提前创建好存储Seq的"/createSeq"结点 CreateMode.PERSISTENT
public static final String SEQ_ZNODE = "/seq"

//通过znode数据版本实现分布式seq生成
public static class Task1 implements Runnable {

private final String taskName;

public Task1(String taskName) {
this.taskName = taskName;
}

@Override
public void run() {
ZkClient zkClient = new ZkClient("192.168.88.153:2181", 3000, 1000);
Stat stat = zkClient.writeData(SEQ_ZNODE, new byte[0], -1);
int versionAsSeq = stat.getVersion();
System.out.println(taskName + " obtain seq=" + versionAsSeq);
zkClient.close();
}
}

//main
final ExecutorService service = Executors.newFixedThreadPool(20);

for (int i = 0; i < 20; i++) {
service.execute(new Task1("[Concurrent-" + i + "]"));
}

2.利用临时带序列号的znode实现和分布式锁持久化znode实现

2.1 下图是利用分布式锁持久化znode实现

客户端采用apache curator 框架，代码：https://code.csdn.net/snippets/929300





2.2利用临时带序列号的znode实现
客户端采用：zkClient （https://github.com/adyliu/zkclient）

//提前创建好锁对象的结点"/lock" CreateMode.PERSISTENT
public static final String LOCK_ZNODE = "/lock";

//分布式锁实现分布式seq生成
public static class Task2 implements Runnable, IZkChildListener {

private final String taskName;

private final ZkClient zkClient;

private final String lockPrefix = "/loc";

private final String selfZnode;

public Task2(String taskName) {
this.taskName = taskName;
zkClient = new ZkClient("192.168.88.153:2181", 30000, 10000);
selfZnode = zkClient.createEphemeralSequential(LOCK_ZNODE + lockPrefix, new byte[0]);
}

@Override
public void run() {
zkClient.subscribeChildChanges(LOCK_ZNODE, this);
do {
} while (zkClient.isConnected());
}

private void createSeq() {
Stat stat = new Stat();
byte[] oldData = zkClient.readData(LOCK_ZNODE, stat);
byte[] newData = update(oldData);
zkClient.writeData(LOCK_ZNODE, newData);
System.out.println(taskName + selfZnode + " obtain seq=" + new String(newData));
}

private byte[] update(byte[] currentData) {
String s = new String(currentData);
int d = Integer.parseInt(s);
d = d + 1;
s = String.valueOf(d);
return s.getBytes();
}

@Override
public void handleChildChange(String parentPath, List<String> currentChildren) throws Exception {
String[] childrensZnode = currentChildren.toArray(new String[currentChildren.size()]);
Arrays.sort(childrensZnode);
String minZnode = LOCK_ZNODE + "/" + childrensZnode[0];
if (selfZnode.equals(minZnode)) {
createSeq();
zkClient.unsubscribeChildChanges(LOCK_ZNODE, this);
zkClient.delete(selfZnode);
zkClient.close();
}
}
}

完整代码参见：https://code.csdn.net/snippets/929320
本文出自 “野马红尘” 博客，请务必保留此出处http://aiilive.blog.51cto.com/1925756/1685614