Apollo源码解析-RemoteConfigRepository

鲁班同学 2019-10-18

1026

RemoteConfigRepository：远程Repository，实现从ConfigService拉取配置，并缓存，支持实时，定时

  public RemoteConfigRepository(String namespace) {
    m_namespace = namespace;
    m_configCache = new AtomicReference<>();
    m_configUtil = ApolloInjector.getInstance(ConfigUtil.class);
    m_httpUtil = ApolloInjector.getInstance(HttpUtil.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);
    gson = new Gson();
    //尝试同步配置
    this.trySync();
//    初始化定时刷新配置定时
    this.schedulePeriodicRefresh();
//    注册自己到RemoteConfigLongPullService，实现配置更新实时通知
    this.scheduleLongPollingRefresh();
  }

解释：构造函数，初次尝试同步配置，初始化刷新配置定时任务，之后注册自己到RemoteConfigLongPollService

进入trySync()

/**
   * 尝试同步
   * @return 是否成功
   */
  protected boolean trySync() {
    try {
      sync();
      return true;
    } catch (Throwable ex) {
      Tracer.logEvent("ApolloConfigException", ExceptionUtil.getDetailMessage(ex));
      logger
          .warn("Sync config failed, will retry. Repository {}, reason: {}", this.getClass(), ExceptionUtil
              .getDetailMessage(ex));
    }
    return false;
  }

解释：这一步主要是尝试同步，返回是否成功

进入sync()

protected synchronized void sync() {
    Transaction transaction = Tracer.newTransaction("Apollo.ConfigService", "syncRemoteConfig");


    try {
//      缓存中的ApolloConfig
      ApolloConfig previous = m_configCache.get();
//      从ConfigServer获得ApolloConfig
      ApolloConfig current = loadApolloConfig();


      //reference equals means HTTP 304
//    如果不相等说明有更新，更新缓存
      if (previous != current) {
        logger.debug("Remote Config refreshed!");
        m_configCache.set(current);
        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();
    }
  }

解释：

1、进入同步，分别从缓存和Config-Service里获取ApolloConfig，对比如果两个不相等，说明有更新，之后更新缓存

2、loadApolloConfig：是从Config-Service实时获取，对应主流程中的4.3实时查询

进入fireRepositoryChange（触发监听者们）

/**
* 触发监听器们
* @param namespace
* @param newProperties
*/
  protected void fireRepositoryChange(String namespace, Properties newProperties) {
    for (RepositoryChangeListener listener : m_listeners) {
      try {
      //通知本地监听者，更新内存配置，本地文件备份
        listener.onRepositoryChange(namespace, newProperties);
      } catch (Throwable ex) {
        Tracer.logError(ex);
        logger.error("Failed to invoke repository change listener {}", listener.getClass(), ex);
      }
    }
  }

总结：

1、初始化RemoteConfigRepository时查询Config-Service的变更配置

2、跟缓存做对比，如果不一样说明有变更

3、通知本地监听者修改本地缓存，备份文件的值

备注：本文主要讲RemoteConfigRepository触发同步，将同步结果更新本地缓存，备份文件操作，具体如何同步请期待下节

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Apollo源码解析-RemoteConfigRepository

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