2分钟了解[Apache]Curator 2分钟了解[Apache]Curator

一句话告诉我Curator是什么?
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(Zookeeper的背景就不在这里介绍了.)
Curator是对ZK的高阶封装. 与操作原生的Zookeeper相比, 它提供了对ZK的完美封装, 简化了对集群的连接, 错误的处理; 实现了一系列经典"模式", 比如分布式锁, Leader选举等.
既然是为了简单首先, 获取一个连接实例(CuratorFramework). 对于每个集群, 只需要创建一个实例.

CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy)

这里我们需要指定一个retryPolicy, 这里用一个指数补偿策略:

RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3) CuratorFramework client = CuratorFrameworkFactory.newClient(zookeeperConnectionString, retryPolicy); client.start();

然后我们就可以调用Zookeeper的一系列操作了, 比如创建:

client.create().forPath("/my/path", myData)

【2分钟了解[Apache]Curator】这里如果出现了连接问题,curator也会帮你自动重连. 所以, 很简单咯?
我们继续, C/R/U/D:

// this will create the given ZNode with the given data client.create().forPath(path, payload); // set data for the given node client.setData().forPath(path, payload); // set data for the given node asynchronously. The completion notification // is done via the CuratorListener. client.setData().inBackground().forPath(path, payload); // delete the given node client.delete().forPath(path); public static List watchedGetChildren(CuratorFramework client, String path) throws Exception { /** * Get children and set a watcher on the node. The watcher notification will come through the * CuratorListener (see setDataAsync() above). */ return client.getChildren().watched().forPath(path); }

模式分布式锁

InterProcessMutex lock = new InterProcessMutex(client, lockPath); if ( lock.acquire(maxWait, waitUnit) ) { try { // do some work inside of the critical section here } finally { lock.release(); } }

Leader选举

LeaderSelectorListener listener = new LeaderSelectorListenerAdapter() { public void takeLeadership(CuratorFramework client) throws Exception { // this callback will get called when you are the leader // do whatever leader work you need to and only exit // this method when you want to relinquish leadership } }LeaderSelector selector = new LeaderSelector(client, path, listener); selector.autoRequeue(); // not required, but this is behavior that you will probably expect selector.start();

事务

Collectionresults = client.inTransaction() .create().forPath("/a/path", "some data".getBytes()) .and() .setData().forPath("/another/path", "other data".getBytes()) .and() .delete().forPath("/yet/another/path") .and() .commit(); // IMPORTANT! The transaction is not submitted until commit() is called

附录

模块	简介
Framework	简化Zookeeper的使用,提供了一系列高阶API, 在Zookeeper集群连接的管理, 以及重连操作上化繁为简.
Receipts	实现了一些ZooKeeper的基本"模式", 该实现基于Curator Framework.
Utilities	一系列工具
Client	ZooKeeper类的替代
Errors	定义了curator如何处理错误,连接问题,可恢复的异常等.
Extensions	实现了一些Zookeeper文档中提及的通用模式.