使用 ZooKeeper 实现分布式队列、分布式锁和选举详解！

由于这个问题涉及的内容较多，我将给出ZooKeeper实现分布式队列和分布式锁的核心代码示例。

分布式队列示例:

public class DistributedQueue {
    private ZooKeeper zk;
    private String queuePath;
 
    public DistributedQueue(ZooKeeper zk, String queuePath) {
        this.zk = zk;
        this.queuePath = queuePath;
        // 确保队列路径存在
        if (exists(queuePath, false) == null) {
            create(queuePath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }
    }
 
    public void put(String nodeData) throws KeeperException, InterruptedException {
        String path = queuePath + "/node-";
        // 创建临时顺序节点
        String newNodePath = create(path, nodeData.getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT_SEQUENTIAL);
    }
 
    public String take() throws KeeperException, InterruptedException {
        List<String> children = getChildren(queuePath, true); // 注册子节点变更监听
        if (children.isEmpty()) {
            return null; // 队列为空
        }
        // 取最小序号节点
        String firstNode = Collections.min(children, new Comparator<String>() {
            public int compare(String lhs, String rhs) {
                return Integer.parseInt(lhs.substring(nodePath.length())) - Integer.parseInt(rhs.substring(nodePath.length()));
            }
        });
        // 删除并返回节点数据
        return new String(getData(queuePath + "/" + firstNode, false, null));
    }
}

分布式锁示例:

public class DistributedLock {
    private ZooKeeper zk;
    private String lockPath;
 
    public DistributedLock(ZooKeeper zk, String lockPath) {
        this.zk = zk;
        this.lockPath = lockPath;
        // 确保锁路径存在
        if (exists(lockPath, false) == null) {
            create(lockPath, new byte[0], ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.PERSISTENT);
        }
    }
 
    public void lock() throws KeeperException, InterruptedException {
        String lockNode = lockPath + "/lock-";
        // 创建临时序列节点
        String newNodePath = create(lockNode, "lock".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE, CreateMode.EPHEMERAL_SEQUENTIAL);
        List<String> children = getChildren(lockPath, false);
        // 获取所有锁节点
        Collections.sort(children);
        // 判断是否获得锁
        if (newNodePath.equals(lockPath + "/" + children.get(0))) {
            // 获得锁
        } else {
            // 等待前一个节点被删除
            waitForDeletion(children.get(0));
            // 再次尝试获得锁