在我们自己的分布式业务系统中，可能会存在某种资源，需要被整个系统的各台服务器共享访问，但是只允许一台服务器同时访问
public class DistributedClientMy {
// 超时时间
private static final int SESSION_TIMEOUT = 5000;
// zookeeper server列表
private String hosts = "spark01:2181,spark02:2181,spark03:2181";
private String groupNode = "locks";
private String subNode = "sub";
private boolean haveLock = false;
private ZooKeeper zk;
// 当前client创建的子节点
private volatile String thisPath;
/**
* 连接zookeeper
*/
public void connectZookeeper() throws Exception {
zk = new ZooKeeper("spark01:2181", SESSION_TIMEOUT, new Watcher() {
public void process(WatchedEvent event) {
try {
// 子节点发生变化
if (event.getType() == EventType.NodeChildrenChanged && event.getPath().equals("/" + groupNode)) {
// thisPath是否是列表中的最小节点
List<String> childrenNodes = zk.getChildren("/" + groupNode, true);
String thisNode = thisPath.substring(("/" + groupNode + "/").length());
// 排序
Collections.sort(childrenNodes);
if (childrenNodes.indexOf(thisNode) == 0) {
doSomething();
thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
}
}
} catch (Exception e) {
e.printStackTrace();
}
}
});
// 创建子节点
thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
// wait一小会, 让结果更清晰一些
Thread.sleep(new Random().nextInt(1000));
// 监听子节点的变化
List<String> childrenNodes = zk.getChildren("/" + groupNode, true);
// 列表中只有一个子节点, 那肯定就是thisPath, 说明client获得锁
if (childrenNodes.size() == 1) {
doSomething();
thisPath = zk.create("/" + groupNode + "/" + subNode, null, Ids.OPEN_ACL_UNSAFE,
CreateMode.EPHEMERAL_SEQUENTIAL);
}
}
/**
* 共享资源的访问逻辑写在这个方法中
*/
private void doSomething() throws Exception {
try {
System.out.println("gain lock: " + thisPath);
Thread.sleep(2000);
// do something
} finally {
System.out.println("finished: " + thisPath);
// 将thisPath删除, 监听thisPath的client将获得通知
// 相当于释放锁
zk.delete(this.thisPath, -1);
}
}
public static void main(String[] args) throws Exception {
DistributedClientMy dl = new DistributedClientMy();
dl.connectZookeeper();
Thread.sleep(Long.MAX_VALUE);
}
}
相关资源：敏捷开发V1.0.pptx