apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/component/config/PortalConfig.java/PortalConfig/getMetaServers
class PortalConfig:  public Map<String, String> getMetaServers() {
    final String key = "apollo.portal.meta.servers";
    String jsonContent = getValue(key);
    if (null == jsonContent) {
      return Collections.emptyMap();
    }

    // watch out that the format of content may be wrong
    // that will cause exception
    Map<String, String> map = Collections.emptyMap();
    try {
      // try to parse
      map = GSON.fromJson(jsonContent, META_SERVERS);
    } catch (Exception e) {
      logger.error("Wrong format for: {}", key, e);
    }
    return map;
  }