最近在工作中，为了完善公司集群服务的架构，提高可用性，降低运维成本，因此开始学习ZooKeeper。
至于什么是ZooKeeper？它能做什么？如何安装ZooKeeper？我就不一一介绍了，类似这些资料网上到处都是。我主要是把在开发过程中，以及个人对ZooKeeper的一些了解记录下来，大家如果遇到类似场景时，希望我的文章能够给你提供一些思路。 我使用的ZooKeeper（以下简称：ZK）客户端是Curator Framework，是Apache的项目，它主要的功能是为ZK的客户端使用提供了高可用的封装。在Curator Framework基础上封装的curator-recipes，实现了很多经典场景。比如：集群管理（Leader选举）、共享锁、队列、Counter等等。可以总结Curator主要解决以下三类问题：- 封装ZK Client与Server之间的连接处理；
- 提供了一套Fluent风格的操作API；
- 提供ZK各种应用场景的抽象封装；
本文主要完成的目标是：Spring PropertyPlaceholderConfigurer配置文件加载器集成ZooKeeper来实现远程配置读取。
配置管理（Configuration Management）。
在集群服务中，可能都会遇到一个问题：那就是当需要修改配置的时候，必须要对每个实例都进行修改，这是一个很繁琐的事情，并且易出错。当然可以使用脚本来解决，但这不是最好的解决办法。OK，Let's go！
我们先看看项目结构
ZooKeeperPropertyPlaceholderConfigurer.java
继承org.springframework.beans.factory.config.PropertyPlaceholderConfigurer，重写processProperties(beanFactoryToProcess, props)来完成远端配置加载的实现
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | package org.bigmouth.common.zookeeper.config.spring; import java.io.UnsupportedEncodingException; import java.util.Properties; import org.apache.commons.lang.StringUtils; import org.bigmouth.common.zookeeper.config.Config; import org.bigmouth.common.zookeeper.config.ZooKeeperConfig; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer; public class ZooKeeperPropertyPlaceholderConfigurer extends PropertyPlaceholderConfigurer { public static final String PATH = "zoo.paths" ; @Override protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props) throws BeansException { super .processProperties(beanFactoryToProcess, props); try { fillCustomProperties(props); System.out.println(props); } catch (Exception e) { // Ignore e.printStackTrace(); } } private void fillCustomProperties(Properties props) throws Exception { byte [] data = getData(props); fillProperties(props, data); } private void fillProperties(Properties props, byte [] data) throws UnsupportedEncodingException { String cfg = new String(data, "UTF-8" ); if (StringUtils.isNotBlank(cfg)) { // 完整的应该还需要处理：多条配置、value中包含=、忽略#号开头 String[] cfgItem = StringUtils.split(cfg, "=" ); props.put(cfgItem[ 0 ], cfgItem[ 1 ]); } } private byte [] getData(Properties props) throws Exception { String path = props.getProperty(PATH); Config config = new ZooKeeperConfig(); return config.getConfig(path); } } |
Config.java
配置操作接口| 1 2 3 4 5 6 7 | package org.bigmouth.common.zookeeper.config; public interface Config { byte [] getConfig(String path) throws Exception; } |
Startup.java
程序启动入口
| 1 2 3 4 5 6 7 8 9 10 11 12 | package org.bigmouth.common.zookeeper.config; import org.springframework.context.support.ClassPathXmlApplicationContext; public class Startup { public static void main(String[] args) { new ClassPathXmlApplicationContext( "classpath:/config/applicationContext.xml" ); } } |
ZooKeeperConfig.java
配置操作接口ZooKeeper的实现
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 | package org.bigmouth.common.zookeeper.config; import org.apache.curator.framework.CuratorFramework; import org.apache.zookeeper.data.Stat; public class ZooKeeperConfig implements Config { @Override public byte [] getConfig(String path) throws Exception { CuratorFramework client = ZooKeeperFactory.get(); if (!exists(client, path)) { throw new RuntimeException( "Path " + path + " does not exists." ); } return client.getData().forPath(path); } private boolean exists(CuratorFramework client, String path) throws Exception { Stat stat = client.checkExists().forPath(path); return !(stat == null ); } } |
ZooKeeperFactory.java
管理ZooKeeper客户端连接
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 | package org.bigmouth.common.zookeeper.config; import org.apache.curator.RetryPolicy; import org.apache.curator.framework.CuratorFramework; import org.apache.curator.framework.CuratorFrameworkFactory; import org.apache.curator.retry.ExponentialBackoffRetry; public class ZooKeeperFactory { public static final String CONNECT_STRING = "172.16.3.42:2181,172.16.3.65:2181,172.16.3.24:2181" ; public static final int MAX_RETRIES = 3 ; public static final int BASE_SLEEP_TIMEMS = 3000 ; public static final String NAME_SPACE = "cfg" ; public static CuratorFramework get() { RetryPolicy retryPolicy = new ExponentialBackoffRetry(BASE_SLEEP_TIMEMS, MAX_RETRIES); CuratorFramework client = CuratorFrameworkFactory.builder() .connectString(CONNECT_STRING) .retryPolicy(retryPolicy) .namespace(NAME_SPACE) .build(); client.start(); return client; } } |
applicationContext.xml
配置加载器使用我们自己创建的ZooKeeperPropertyPlaceholderConfigurer，因为它重写了processProperties方法。这个方法里会去读取远程配置。
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | <? xml version = "1.0" encoding = "UTF-8" ?> <!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" ""> < beans > < bean class = "org.bigmouth.common.zookeeper.config.spring.ZooKeeperPropertyPlaceholderConfigurer" > < property name = "systemPropertiesModeName" value = "SYSTEM_PROPERTIES_MODE_OVERRIDE" /> < property name = "ignoreResourceNotFound" value = "true" /> < property name = "locations" > < list > < value >classpath:application.properties</ value > </ list > </ property > </ bean > </ beans > |
application.properties
项目配置文件，里面除了配置ZooKeeper服务器地址和读取的节点以外，其他所有的配置都应该保存在ZooKeeper中。
| 1 | zoo.paths=/properties |
设置ZooKeeper数据
登录ZooKeeper中为节点 /cfg/properties 添加一条配置项：
如图所示：我创建了一个节点 /cfg/properties 并设置内容为：jdbc.driver=org.postgresql.Driver
运行Startup.java
OK 了，zoo.paths是本地application.properties文件中的，jdbc.driver是远程ZooKeeper服务器中的。
项目中需要依赖的jar包
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | < dependency > < groupId >commons-lang</ groupId > < artifactId >commons-lang</ artifactId > < version >2.4</ version > </ dependency > < dependency > < groupId >org.springframework</ groupId > < artifactId >spring-core</ artifactId > < version >3.0.3.RELEASE</ version > </ dependency > < dependency > < groupId >org.springframework</ groupId > < artifactId >spring-context</ artifactId > < version >3.0.3.RELEASE</ version > </ dependency > < dependency > < groupId >org.springframework</ groupId > < artifactId >spring-tx</ artifactId > < version >3.0.3.RELEASE</ version > </ dependency > < dependency > < groupId >org.springframework</ groupId > < artifactId >spring-context-support</ artifactId > < version >3.0.3.RELEASE</ version > </ dependency > <!-- ZooKeeper --> < dependency > < groupId >org.apache.zookeeper</ groupId > < artifactId >zookeeper</ artifactId > < version >3.4.6</ version > </ dependency > < dependency > < groupId >org.apache.curator</ groupId > < artifactId >curator-framework</ artifactId > < version >2.4.2</ version > </ dependency > < dependency > < groupId >org.apache.curator</ groupId > < artifactId >curator-recipes</ artifactId > < version >2.4.2</ version > </ dependency > |