apollo-client/src/main/java/com/ctrip/framework/apollo/internals/DefaultConfig.java/DefaultConfig/tryWarnLog
class DefaultConfig:  protected void tryWarnLog(String value) {
    if (value == null && m_configProperties.get() == null && m_warnLogRateLimiter.tryAcquire()) {
      logger.warn(
          "Could not load config for namespace {} from Apollo, please check whether the configs are released in Apollo! Return default value now!",
          m_namespace);
    }
  }