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Springboot源码分析之apollo配置 文章目录 系列文章目录前言一、apollo是如何完成初始化的,拉取配置的呢1. apollo的初始化阶段2.初始化RemoteConfigRepository3.同步远程配置4.发布ConfigFileChangeEvent事件 总结 前言
配置中心我相信有一年开发经验的程序员都…系列文章目录
Springboot源码分析之apollo配置 文章目录 系列文章目录前言一、apollo是如何完成初始化的,拉取配置的呢1. apollo的初始化阶段2.初始化RemoteConfigRepository3.同步远程配置4.发布ConfigFileChangeEvent事件 总结 前言
配置中心我相信有一年开发经验的程序员都听过吧有三年开发经验的程序100%都使用过配置中心配置吧。apollo做为常用的配置中心你知道它的原理吗你知道它是怎么集成到springboot的吗 本篇文章带你了解其原理让你也能够自定义组件。 一、apollo是如何完成初始化的,拉取配置的呢
1. apollo的初始化阶段
Springboot环境准备阶段发布ApplicationEnvironmentPreparedEvent 事件EnvironmentPostProcessorApplicationListener 监听到事件之后 执行 postProcessEnvironment方法。apollo 中 的初始化类 ApolloApplicationContextInitializer 就实现EnvironmentPostProcessor接口。 ApolloApplicationContextInitializer public void postProcessEnvironment(ConfigurableEnvironment configurableEnvironment, SpringApplication springApplication) {// should always initialize system properties like app.id in the first placeinitializeSystemProperty(configurableEnvironment);Boolean eagerLoadEnabled configurableEnvironment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_EAGER_LOAD_ENABLED, Boolean.class, false);//EnvironmentPostProcessor should not be triggered if you dont want Apollo Loading before Logging System Initializationif (!eagerLoadEnabled) {return;}Boolean bootstrapEnabled configurableEnvironment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, Boolean.class, false);if (bootstrapEnabled) {DeferredLogger.enable();//重点实现逻辑的方法initialize(configurableEnvironment);}}2.初始化RemoteConfigRepository
经过initialize()方法层层调用最后进入到RemoteConfigRepository init public RemoteConfigRepository(String namespace) {m_namespace namespace;m_configCache new AtomicReference();m_configUtil ApolloInjector.getInstance(ConfigUtil.class);m_httpClient ApolloInjector.getInstance(HttpClient.class);m_serviceLocator ApolloInjector.getInstance(ConfigServiceLocator.class);remoteConfigLongPollService ApolloInjector.getInstance(RemoteConfigLongPollService.class);m_longPollServiceDto new AtomicReference();m_remoteMessages new AtomicReference();m_loadConfigRateLimiter RateLimiter.create(m_configUtil.getLoadConfigQPS());m_configNeedForceRefresh new AtomicBoolean(true);m_loadConfigFailSchedulePolicy new ExponentialSchedulePolicy(m_configUtil.getOnErrorRetryInterval(),m_configUtil.getOnErrorRetryInterval() * 8);//下面三个方法就是拉去配置的核心代码了 //同步远程配置 this.trySync();//固定频率刷新、内部实现也是调用trySync()this.schedulePeriodicRefresh();//轮询访问远程配置中心每次访问直到超时或者apollo 配置发生变化this.scheduleLongPollingRefresh();}3.同步远程配置
AbstractConfigRepository.trySync()同步远程配置方法方法内部主要实现逻辑在sync()中
protected synchronized void sync() {Transaction transaction Tracer.newTransaction(Apollo.ConfigService, syncRemoteConfig);try {//m_configCache ApolloConfig previous m_configCache.get();//加载 远程 apollo configApolloConfig current loadApolloConfig();//reference equals means HTTP 304if (previous ! current) {logger.debug(Remote Config refreshed!);m_configCache.set(current);//getConfig 方法 将apollo配置放进 properties中this.fireRepositoryChange(m_namespace, this.getConfig());}if (current ! null) {Tracer.logEvent(String.format(Apollo.Client.Configs.%s, current.getNamespaceName()),current.getReleaseKey());}transaction.setStatus(Transaction.SUCCESS);} catch (Throwable ex) {transaction.setStatus(ex);throw ex;} finally {transaction.complete();}}private volatile AtomicReferenceApolloConfig m_configCache; 使用了volatile 修饰原子引用类型进行封装引用这就是看源码的意义吧 4.发布ConfigFileChangeEvent事件
sync() 方法中的 调用fireRepositoryChange(),最后会调用到AbstractConfigFile.fireConfigChange()方法 private void fireConfigChange(final ConfigFileChangeEvent changeEvent) {for (final ConfigFileChangeListener listener : m_listeners) {m_executorService.submit(new Runnable() {Overridepublic void run() {String listenerName listener.getClass().getName();Transaction transaction Tracer.newTransaction(Apollo.ConfigFileChangeListener, listenerName);try {//listner 是一个PropertySourcesProcessor 中的一个lambda 类//ConfigChangeListener configChangeEventPublisher changeEvent -//applicationEventPublisher.publishEvent(new ApolloConfigChangeEvent(changeEvent));listener.onChange(changeEvent);transaction.setStatus(Transaction.SUCCESS);} catch (Throwable ex) {transaction.setStatus(ex);Tracer.logError(ex);logger.error(Failed to invoke config file change listener {}, listenerName, ex);} finally {transaction.complete();}}});}}因此我们可以监听ApolloConfigChangeEvent事件来监听apollo配置是否发生产变化 eg
public class ListenerApollo implements ConfigChangeListener, ApplicationListenerApolloConfigChangeEvent {Overridepublic void onChange(ConfigChangeEvent configChangeEvent) {//核心线程配置发生变化、重新setConfigChange coreSize configChangeEvent.getChange(threadPool.corePoolSize);if( coreSize! null){ThreadPoolExecutor executor SpringUtil.getBean(ThreadPoolExecutor.class);executor.setCorePoolSize(Integer.valueOf(coreSize.getNewValue()));}}Overridepublic void onApplicationEvent(ApolloConfigChangeEvent event) {this.onChange(event.getConfigChangeEvent());}
}总结
分析apollo在Springboot启动的哪个环节被集成初始化的以及跟了同步远程配置的逻辑初始化时同步一次定时同步长轮询监听配置是否发生变化发生变化又通知程序进行同步。并且同步后也会发布一个ApolloConfigChangeEvent事件,放开发者去监听配置变化。
