code: public static FaultToleranceConfig getConfig(String appName) {
          if (appName == null) {
              return DEFAULT_CFG;
          } else {
              FaultToleranceConfig config = APP_CONFIGS.get(appName);
              return config == null ? DEFAULT_CFG : config;
          }
      }
docs: Get config if absent, else return default
  
  @param appName App name
  @return FaultToleranceConfig of this app, or default config