apollo-core/src/main/java/com/ctrip/framework/apollo/core/MetaDomainConsts.java/MetaDomainConsts/getDomain
class MetaDomainConsts:  public static String getDomain(Env env) {
    String metaServerAddress = getMetaServerAddress(env);
    // if there is more than one address, need to select one
    if (metaServerAddress.contains(",")) {
      return selectMetaServerAddress(metaServerAddress);
    }
    return metaServerAddress;
  }