9Nacos配置中心之加载配置客户端和服务端的处理

一 客户端配置中心之加载配置

我们接着上个文章说的，Springboot启动的时候调用prep在reEnvironment()进行环境准备，
prepareEnvironment()进行环境准备，在启动类执行完prepareEnvironment后，执行prepareContext进行刷新应用上下文件的准备
代码如下：

public ConfigurableApplicationContext run(String... args) {
   StopWatch stopWatch = new StopWatch();
   stopWatch.start();
   ConfigurableApplicationContext context = null;
   Collection<SpringBootExceptionReporter> exceptionReporters = new ArrayList<>();
   configureHeadlessProperty();
   SpringApplicationRunListeners listeners = getRunListeners(args);
   listeners.starting();
   try {
      ApplicationArguments applicationArguments = new DefaultApplicationArguments(
            args);
       //环境准备
      ConfigurableEnvironment environment = prepareEnvironment(listeners,
            applicationArguments);
      configureIgnoreBeanInfo(environment);
      Banner printedBanner = printBanner(environment);
      context = createApplicationContext();
      exceptionReporters = getSpringFactoriesInstances(
            SpringBootExceptionReporter.class,
            new Class[] { ConfigurableApplicationContext.class }, context);
      prepareContext(context, environment, listeners, applicationArguments,
            printedBanner);
      refreshContext(context);
      afterRefresh(context, applicationArguments);
      stopWatch.stop();
      if (this.logStartupInfo) {
         new StartupInfoLogger(this.mainApplicationClass)
               .logStarted(getApplicationLog(), stopWatch);
      }
      listeners.started(context);
      callRunners(context, applicationArguments);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, listeners);
      throw new IllegalStateException(ex);
   }

   try {
      listeners.running(context);
   }
   catch (Throwable ex) {
      handleRunFailure(context, ex, exceptionReporters, null);
      throw new IllegalStateException(ex);
   }
   return context;
}

我们看一下prepareContext()准备上下文方法做了什么

prepareContext()方法

private void prepareContext(ConfigurableApplicationContext context,
      ConfigurableEnvironment environment, SpringApplicationRunListeners listeners,
      ApplicationArguments applicationArguments, Banner printedBanner) {
   context.setEnvironment(environment);
   postProcessApplicationContext(context);
   applyInitializers(context);
   listeners.contextPrepared(context);
   if (this.logStartupInfo) {
      logStartupInfo(context.getParent() == null);
      logStartupProfileInfo(context);
   }
   // Add boot specific singleton beans
   ConfigurableListableBeanFactory beanFactory = context.getBeanFactory();
   beanFactory.registerSingleton("springApplicationArguments", applicationArguments);
   if (printedBanner != null) {
      beanFactory.registerSingleton("springBootBanner", printedBanner);
   }
   if (beanFactory instanceof DefaultListableBeanFactory) {
      ((DefaultListableBeanFactory) beanFactory)
            .setAllowBeanDefinitionOverriding(this.allowBeanDefinitionOverriding);
   }
   // Load the sources
   Set<Object> sources = getAllSources();
   Assert.notEmpty(sources, "Sources must not be empty");
   load(context, sources.toArray(new Object[0]));
   listeners.contextLoaded(context);
}

1. 调用applyInitializers()方法
2. 注册打印banner图的单例bean
3. 加载资源

我们再看一下applyInitializers()方法是做什么的

applyInitializers()方法

@SuppressWarnings({ "rawtypes", "unchecked" })
protected void applyInitializers(ConfigurableApplicationContext context) {
   for (ApplicationContextInitializer initializer : getInitializers()) {
      Class<?> requiredType = GenericTypeResolver.resolveTypeArgument(
            initializer.getClass(), ApplicationContextInitializer.class);
      Assert.isInstanceOf(requiredType, context, "Unable to call initializer.");
      initializer.initialize(context);
   }
}

PropertySourceBootstrapConfiguration实现了ApplicationContextInitializer接口，所以会调用PropertySourceBootstrapConfiguration的initialize()方法

PropertySourceBootstrapConfiguration的initialize()方法

@Override
public void initialize(ConfigurableApplicationContext applicationContext) {
   CompositePropertySource composite = new CompositePropertySource(
         BOOTSTRAP_PROPERTY_SOURCE_NAME);
   AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
   boolean empty = true;
   ConfigurableEnvironment environment = applicationContext.getEnvironment();
   for (PropertySourceLocator locator : this.propertySourceLocators) {
      PropertySource<?> source = null;
       //加载
      source = locator.locate(environment);
      if (source == null) {
         continue;
      }
      logger.info("Located property source: " + source);
      composite.addPropertySource(source);
      empty = false;
   }
   if (!empty) {
      MutablePropertySources propertySources = environment.getPropertySources();
      String logConfig = environment.resolvePlaceholders("${logging.config:}");
      LogFile logFile = LogFile.get(environment);
      if (propertySources.contains(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
         propertySources.remove(BOOTSTRAP_PROPERTY_SOURCE_NAME);
      }
      insertPropertySources(propertySources, composite);
      reinitializeLoggingSystem(environment, logConfig, logFile);
      setLogLevels(applicationContext, environment);
      handleIncludedProfiles(environment);
   }
}

locator.locate(environment)方法会调用NacosPropertySourceLocator的locate方法，这就是加载配置的关键代码了

NacosPropertySourceLocator的locate()方法

@Override
public PropertySource<?> locate(Environment env) {

   ConfigService configService = nacosConfigProperties.configServiceInstance();

   if (null == configService) {
      log.warn("no instance of config service found, can't load config from nacos");
      return null;
   }
   long timeout = nacosConfigProperties.getTimeout();
   nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService,
         timeout);
   String name = nacosConfigProperties.getName();

   String dataIdPrefix = nacosConfigProperties.getPrefix();
   if (StringUtils.isEmpty(dataIdPrefix)) {
      dataIdPrefix = name;
   }

   if (StringUtils.isEmpty(dataIdPrefix)) {
      dataIdPrefix = env.getProperty("spring.application.name");
   }

   CompositePropertySource composite = new CompositePropertySource(
         NACOS_PROPERTY_SOURCE_NAME);

   loadSharedConfiguration(composite);
   loadExtConfiguration(composite);
   loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);

   return composite;
}

1. 初始化ConfigService对象，ConfigService是Nacos客户端提供的用于访问实现配置中心基本操作的类
2. 如果为空打印支持没有ConfigService实例，不能加载配置，返回空
3. 如果不为空，按照顺序分别加载共享配置、扩展配置、应用名称对应的配置。

进入loadApplicationConfiguration-》loadNacosDataIfPresent-》loadNacosPropertySource-》build-》loadNacosData

loadNacosData()方法

private Properties loadNacosData(String dataId, String group, String fileExtension) {
   String data = null;
   try {
      data = configService.getConfig(dataId, group, timeout);
      if (StringUtils.isEmpty(data)) {
         log.warn(
               "Ignore the empty nacos configuration and get it based on dataId[{}] & group[{}]",
               dataId, group);
         return EMPTY_PROPERTIES;
      }
      log.info(String.format(
            "Loading nacos data, dataId: '%s', group: '%s', data: %s", dataId,
            group, data));

      Properties properties = NacosDataParserHandler.getInstance()
            .parseNacosData(data, fileExtension);
      return properties == null ? EMPTY_PROPERTIES : properties;
   }
   catch (NacosException e) {
      log.error("get data from Nacos error,dataId:{}, ", dataId, e);
   }
   catch (Exception e) {
      log.error("parse data from Nacos error,dataId:{},data:{},", dataId, data, e);
   }
   return EMPTY_PROPERTIES;
}

configService.getConfig方法从Nacos配置中心上加载配置进行填充

private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {
    group = null2defaultGroup(group);
    ParamUtils.checkKeyParam(dataId, group);
    ConfigResponse cr = new ConfigResponse();

    cr.setDataId(dataId);
    cr.setTenant(tenant);
    cr.setGroup(group);

    // 优先使用本地配置
    String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant);
    if (content != null) {
        LOGGER.warn("[{}] [get-config] get failover ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
            dataId, group, tenant, ContentUtils.truncateContent(content));
        cr.setContent(content);
        configFilterChainManager.doFilter(null, cr);
        content = cr.getContent();
        return content;
    }

    try {
        content = worker.getServerConfig(dataId, group, tenant, timeoutMs);

        cr.setContent(content);

        configFilterChainManager.doFilter(null, cr);
        content = cr.getContent();

        return content;
    } catch (NacosException ioe) {
        if (NacosException.NO_RIGHT == ioe.getErrCode()) {
            throw ioe;
        }
        LOGGER.warn("[{}] [get-config] get from server error, dataId={}, group={}, tenant={}, msg={}",
            agent.getName(), dataId, group, tenant, ioe.toString());
    }

    LOGGER.warn("[{}] [get-config] get snapshot ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
        dataId, group, tenant, ContentUtils.truncateContent(content));
    content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant);
    cr.setContent(content);
    configFilterChainManager.doFilter(null, cr);
    content = cr.getContent();
    return content;
}

方法中优先加载本地的配置，如果不为空就返回结果，否则这里又会调用ClientWork的getServerConfig()方法获取内容然后返回结果

ClientWork的getServerConfig()方法

public String getServerConfig(String dataId, String group, String tenant, long readTimeout)
    throws NacosException {
    if (StringUtils.isBlank(group)) {
        group = Constants.DEFAULT_GROUP;
    }

    HttpResult result = null;
    try {
        List<String> params = null;
        if (StringUtils.isBlank(tenant)) {
            params = Arrays.asList("dataId", dataId, "group", group);
        } else {
            params = Arrays.asList("dataId", dataId, "group", group, "tenant", tenant);
        }
        //发起请求
        result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);
    } catch (IOException e) {
        String message = String.format(
            "[%s] [sub-server] get server config exception, dataId=%s, group=%s, tenant=%s", agent.getName(),
            dataId, group, tenant);
        LOGGER.error(message, e);
        throw new NacosException(NacosException.SERVER_ERROR, e);
    }

    switch (result.code) {
        case HttpURLConnection.HTTP_OK:
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.content);
            return result.content;
        case HttpURLConnection.HTTP_NOT_FOUND:
            LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null);
            return null;
        case HttpURLConnection.HTTP_CONFLICT: {
            LOGGER.error(
                "[{}] [sub-server-error] get server config being modified concurrently, dataId={}, group={}, "
                    + "tenant={}", agent.getName(), dataId, group, tenant);
            throw new NacosException(NacosException.CONFLICT,
                "data being modified, dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
        }
        case HttpURLConnection.HTTP_FORBIDDEN: {
            LOGGER.error("[{}] [sub-server-error] no right, dataId={}, group={}, tenant={}", agent.getName(), dataId,
                group, tenant);
            throw new NacosException(result.code, result.content);
        }
        default: {
            LOGGER.error("[{}] [sub-server-error]  dataId={}, group={}, tenant={}, code={}", agent.getName(), dataId,
                group, tenant, result.code);
            throw new NacosException(result.code,
                "http error, code=" + result.code + ",dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
        }
    }
}

现在水落石出了，这里调用客户端向服务端发送请求，agent.httpGet()发起请求，请求路径：/v1/cs/configs

二 服务端/v1/cs/configs接口的处理

服务端在nacos.config包下，ConfigController类的getConfig()方法

@GetMapping
@Secured(action = ActionTypes.READ, signType = SignType.CONFIG)
public void getConfig(HttpServletRequest request, HttpServletResponse response,
        @RequestParam("dataId") String dataId, @RequestParam("group") String group,
        @RequestParam(value = "tenant", required = false, defaultValue = StringUtils.EMPTY) String tenant,
        @RequestParam(value = "tag", required = false) String tag)
        throws IOException, ServletException, NacosException {
    // check tenant
    ParamUtils.checkTenant(tenant);
    tenant = NamespaceUtil.processNamespaceParameter(tenant);
    // check params
    ParamUtils.checkParam(dataId, group, "datumId", "content");
    ParamUtils.checkParam(tag);
    
    final String clientIp = RequestUtil.getRemoteIp(request);
    String isNotify = request.getHeader("notify");
    inner.doGetConfig(request, response, dataId, group, tenant, tag, isNotify, clientIp);
}

调用了ConfigServletInner的doGetConfig()方法，调用tryConfigReadLock()方法加入读锁，查看缓存中有没有nacos中配置的key 有的话就加锁成功了，加锁成功后调用ConfigCacheService.getContentCache()获取CacheItem实例，然后判断，然后根据配置信息等选择从数据库取数据还是获取本地文件，然后返回文件内容返回给客户端

总结

启动类执行完prepareEnvironment后，执行prepareContext进行刷新应用上下文件的准备，调用applyInitializers，调用NacosPropertySourceLocator的locate方法，初始化ConfigService对象，按照顺序分别加载共享配置、扩展配置、应用名称对应的配置，进入loadNacosData方法，然后configService.getConfig方法从Nacos配置中心上加载配置进行填充。

这就是nacos初始化的大体流程，如果我们在工作中遇到获取nacos数据获取不到的时候，我们可以试着跟踪一下nacos加载数据的流程，分析问题，定位问题，及时解决。