本文主要是介绍使用Apache Curator监控Zookeeper的Node和Path的状态,希望对大家解决编程问题提供一定的参考价值,需要的开发者们随着小编来一起学习吧!
1.Zookeeper经常被我们用来做配置管理,配置的管理在分布式应用环境中很常见,例如同一个应用系统需要多台 PC Server 运行,但是它们运行的应用系统的某些配置项是相同的,如果要修改这些相同的配置项,那么就必须同时修改每台运行这个应用系统的 PC Server,这样非常麻烦而且容易出错。像这样的配置信息完全可以交给 Zookeeper 来管理,将配置信息保存在 Zookeeper 的某个目录节点中,然后将所有需要修改的应用机器监控配置信息的状态,一旦配置信息发生变化,每台应用机器就会收到 Zookeeper 的通知,然后从 Zookeeper 获取新的配置信息应用到系统中。
我们通过Curator是如何实现的呢? 那就是NodeCache,关于如何实现,后面代码给出说明。
假如我们有多个服务保存在Zookeeper的/services下,例如/services/service1,/services/service2......在service1,servce2下,保存的有服务的ip,端口等信息。如果我们需要增加服务,或者某个服务不可用了,从Zookeeper中删除了,或者我们修改了某个Service下的ip和端口值,我们有必要第一时间内收到通知,已进行相应的处理,这时候可以怎么办呢? Curator提供了一个pathChildrenCache来满足我们的需求。下面我们给出代码来说明两个的用法.
package com.hupengcool.cache;import org.apache.curator.framework.CuratorFramework;
import org.apache.curator.framework.CuratorFrameworkFactory;
import org.apache.curator.framework.recipes.cache.ChildData;
import org.apache.curator.framework.recipes.cache.NodeCache;
import org.apache.curator.framework.recipes.cache.NodeCacheListener;
import org.apache.curator.framework.recipes.cache.PathChildrenCache;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheEvent;
import org.apache.curator.framework.recipes.cache.PathChildrenCacheListener;
import org.apache.curator.retry.ExponentialBackoffRetry;
import org.apache.curator.utils.CloseableUtils;
import org.apache.curator.utils.EnsurePath;import java.util.List;/*** Created by hupeng on 2014/9/19.*/
public class Cache {public static PathChildrenCache pathChildrenCache(CuratorFramework client, String path, Boolean cacheData) throws Exception {final PathChildrenCache cached = new PathChildrenCache(client, path, cacheData);cached.getListenable().addListener(new PathChildrenCacheListener() { @Overridepublic void childEvent(CuratorFramework client, PathChildrenCacheEvent event) throws Exception {PathChildrenCacheEvent.Type eventType = event.getType();switch (eventType) {case CONNECTION_RECONNECTED:cached.rebuild();break;case CONNECTION_SUSPENDED:case CONNECTION_LOST:System.out.println("Connection error,waiting...");break;default:System.out.println("PathChildrenCache changed : {path:" + event.getData().getPath() + " data:" +new String(event.getData().getData()) + "}");}}});return cached;}public static NodeCache nodeCache(CuratorFramework client, String path) {final NodeCache cache = new NodeCache(client, path);cache.getListenable().addListener(new NodeCacheListener() {@Overridepublic void nodeChanged() throws Exception {System.out.println("NodeCache changed, data is: " + new String(cache.getCurrentData().getData()));}});return cache;}public static void main(String[] args) throws Exception {ExponentialBackoffRetry retryPolicy = new ExponentialBackoffRetry(1000, 3);CuratorFramework client = CuratorFrameworkFactory.newClient("127.0.0.1", retryPolicy);client.start();EnsurePath ensurePath = client.newNamespaceAwareEnsurePath("/create/test");ensurePath.ensure(client.getZookeeperClient());/*** pathChildrenCache*/PathChildrenCache cache = pathChildrenCache(client, "/create", true);cache.start(PathChildrenCache.StartMode.BUILD_INITIAL_CACHE);List<ChildData> datas = cache.getCurrentData();for (ChildData data : datas) {System.out.println("pathcache:{" + data.getPath() + ":" + new String(data.getData())+"}");}/*** NodeCache*/NodeCache nodeCache = nodeCache(client, "/create/test");nodeCache.start(true);client.setData().forPath("/create/test", "1111".getBytes());System.out.println(new String(nodeCache.getCurrentData().getData()));Thread.sleep(10000);CloseableUtils.closeQuietly(cache);CloseableUtils.closeQuietly(client);}
}
转载自:http://www.cnblogs.com/hupengcool/p/3982301.html
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