apollo-biz/src/main/java/com/ctrip/framework/apollo/biz/service/NamespaceBranchService.java/NamespaceBranchService/findBranchGrayRules
class NamespaceBranchService:  public GrayReleaseRule findBranchGrayRules(String appId, String clusterName, String namespaceName,
                                             String branchName) {
    return grayReleaseRuleRepository
        .findTopByAppIdAndClusterNameAndNamespaceNameAndBranchNameOrderByIdDesc(appId, clusterName, namespaceName, branchName);
  }