看过Zookeeper相关文档后都知道它可以实现分布式集群的配置管理,本文以一个简单的实例来演示它是如何实现的并工作的。
情景需要,简单理解为下图:
一个web集群,需要通过zk来控制集群的日志输出级别,比如管理员需要在生产环境下查看一下DEBUG日志,他可以临时将集群的日志输出级别改为DEBUG,获取他想要的信息后还要将级别调回到INFO或者ERROR级别。
今天的主角是Curator-Framework,它的存在使得我们操作ZK变得简单有趣起来!
环境,框架,工具
- Zookeeper集群
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- Maven + IDEA
POM
依赖关系和jetty插件
org.springframework spring-context 3.2.3.RELEASE org.springframework spring-web 3.2.3.RELEASE org.springframework spring-webmvc 3.2.3.RELEASE org.apache.zookeeper zookeeper 3.4.5 log4j log4j org.slf4j slf4j-log4j12 org.apache.curator curator-framework 2.0.1-incubating org.apache.curator curator-recipes 2.0.1-incubating ch.qos.logback logback-classic 1.0.13 1.7.5 org.slf4j slf4j-api org.testng testng 6.8.5 test zookeeper-configuration org.mortbay.jetty jetty-maven-plugin 8.1.7.v20120910 pbase 8080
WEB.XML
这个不用解释了,地球人都知道
Archetype Created Web Application contextConfigLocation classpath*:/applicationContext.xml org.springframework.web.context.ContextLoaderListener springServlet org.springframework.web.servlet.DispatcherServlet contextConfigLocation classpath*:/spring-mvc.xml 1 springServlet /
Spring 配置
applicationContext.xml
spring-mvc.xml
Zookeeper配置管理实现相关类
ZookeeperFactoryBean.java
在Spring Context加载过程中创建Zookeeper链接对像并设置触发监听,通过Curator.
package cn.bg.zk.core;public class ZookeeperFactoryBean implements FactoryBean , InitializingBean, DisposableBean { private Logger logger = LoggerFactory.getLogger(this.getClass()); private CuratorFramework zkClient; //设置Zookeeper启动后需要调用的监听或者,或者需要做的初始化工作。 public void setListeners(List listeners) { this.listeners = listeners; } private List listeners; //设置ZK链接串 public void setZkConnectionString(String zkConnectionString) { this.zkConnectionString = zkConnectionString; } private String zkConnectionString; @Override public CuratorFramework getObject() { return zkClient; } @Override public Class getObjectType() { return CuratorFramework.class; } @Override public boolean isSingleton() { return true; } @Override public void destroy() throws Exception { zkClient.close(); } //创建ZK链接 @Override public void afterPropertiesSet(){ //1000 是重试间隔时间基数,3 是重试次数 RetryPolicy retryPolicy = new ExponentialBackoffRetry(1000, 3); zkClient = createWithOptions(zkConnectionString, retryPolicy, 2000, 10000); registerListeners(zkClient); zkClient.start(); } /** * 通过自定义参数创建 */ public CuratorFramework createWithOptions(String connectionString, RetryPolicy retryPolicy, int connectionTimeoutMs, int sessionTimeoutMs) { return CuratorFrameworkFactory.builder() .connectString(connectionString) .retryPolicy(retryPolicy) .connectionTimeoutMs(connectionTimeoutMs) .sessionTimeoutMs(sessionTimeoutMs) .build(); } //注册需要监听的监听者对像. private void registerListeners(CuratorFramework client){ client.getConnectionStateListenable().addListener(new ConnectionStateListener() { @Override public void stateChanged(CuratorFramework client, ConnectionState newState) { logger.info("CuratorFramework state changed: {}", newState); if(newState == ConnectionState.CONNECTED || newState == ConnectionState.RECONNECTED){ for(IZKListener listener : listeners){ listener.executor(client); logger.info("Listener {} executed!", listener.getClass().getName()); } } } }); client.getUnhandledErrorListenable().addListener(new UnhandledErrorListener() { @Override public void unhandledError(String message, Throwable e) { logger.info("CuratorFramework unhandledError: {}", message); } }); }}
监听事件接口
所有需要在ZK客户端链接成功后需要做的事件,需要实现这个接口,由上面的ZookeeperFactoryBean统一调度。
package cn.bg.zk.core;import org.apache.curator.framework.CuratorFramework;public interface IZKListener { void executor(CuratorFramework client);}
Logback监听实现
这里主要用到Curator的NodeCache类,它的主要功能是用来监听znode本身的变化,并可以获取当前值,而且会自动重复监听,简化了原生API开发的繁琐过程。
package cn.bg.zk.configuration;public class LogbackLevelListener implements IZKListener { //获取logback实例 Logger log = (Logger) LoggerFactory.getLogger(this.getClass()); private String path; //Logback日志级别ZNode public LogbackLevelListener(String path) { this.path = path; } @Override public void executor(CuratorFramework client) { //使用Curator的NodeCache来做ZNode的监听,不用我们自己实现重复监听 final NodeCache cache = new NodeCache(client, path); cache.getListenable().addListener(new NodeCacheListener() { @Override public void nodeChanged() throws Exception { byte[] data = cache.getCurrentData().getData(); //设置日志级别 if (data != null) { String level = new String(data); Logger logger = (Logger) LoggerFactory.getLogger("root"); Level newLevel = Level.fromLocationAwareLoggerInteger(Integer.parseInt(level)); logger.setLevel(newLevel); System.out.println("Setting logback new level to :" + newLevel.levelStr); } } }); try { cache.start(true); } catch (Exception e) { log.error("Start NodeCache error for path: {}, error info: {}", path, e.getMessage()); } }}
通过WEB端查看当前日志级别
写一个controller来读取logback的日志级别
MainController.java
package cn.bg.controller;@Controllerpublic class MainController { @RequestMapping("/") @ResponseBody public String logbackLevel() throws Exception { Logger logger = (Logger) LoggerFactory.getLogger("root"); String levelStr = logger.getLevel().levelStr; return levelStr; }}
运行
在ZK集群端启动zkCli创建/zk_test/logbacklevel的znode,设置值为10,或20在控制台来查看logback的日志输出情况,logback日志级别数据表示如下:
TRACE_INT = 0DEBUG_INT = 10INFO_INT = 20WARN_INT = 30ERROR_INT = 40
到此就实现了一个简单的ZK配置管理情境,有了Curator-Framework后一切变的简单起来,我们主要精力只要解决业务相关的的需要,而ZK相关的实现由Curator来解决。
下一篇介绍Curator分布式队列实现。