apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/service/NamespaceBranchService.java/NamespaceBranchService/deleteBranch
class NamespaceBranchService:  public void deleteBranch(String appId, Env env, String clusterName, String namespaceName,
                           String branchName, String operator) {
    namespaceBranchAPI.deleteBranch(appId, env, clusterName, namespaceName, branchName, operator);

    Tracer.logEvent(TracerEventType.DELETE_GRAY_RELEASE,
            String.format("%s+%s+%s+%s", appId, env, clusterName, namespaceName));
  }