使用Apache Curator监控Zookeeper的Node和Path的状态

　1.Zookeeper常常被咱们用来作配置管理，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须要多台 PC Server 运行，可是它们运行的应用系统的某些配置项是相同的，若是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，这样很是麻烦并且容易出错。像这样的配置信息彻底能够交给 Zookeeper 来管理，将配置信息保存在 Zookeeper 的某个目录节点中，而后将全部须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，而后从 Zookeeper 获取新的配置信息应用到系统中。                                                                                      

　　咱们经过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。

　　假如咱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。若是咱们须要增长服务，或者某个服务不可用了，从Zookeeper中删除了，或者咱们修改了某个Service下的ip和端口值，咱们有必要第一时间内收到通知，已进行相应的处理，这时候能够怎么办呢？ Curator提供了一个pathChildrenCache来知足咱们的需求。下面咱们给出代码来讲明两个的用法.

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() { 
            @Override
            public 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() {
            @Override
            public 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);
    }
}

 

Curator Cache简介：https://www.cnblogs.com/francisYoung/p/5483777.html?utm_source=tuicool&utm_medium=referral

Zookeeper开源客户端框架Curator简介：http://macrochen.iteye.com/blog/1366136/