fix response to omitempty (#5953)

Signed-off-by: Ben Ye <benye@amazon.com>

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [ENHANCEMENT] Distributor/Ring: Allow disabling detailed ring metrics by ring member. #5931
 * [ENHANCEMENT] KV: Etcd Added etcd.ping-without-stream-allowed parameter to disable/enable  PermitWithoutStream #5933
 * [CHANGE] Upgrade Dockerfile Node version from 14x to 18x. #5906
+* [CHANGE] Query Frontend/Ruler: Omit empty data field in API response. #5953
 * [BUGFIX] Configsdb: Fix endline issue in db password. #5920
 * [BUGFIX] Ingester: Fix `user` and `type` labels for the `cortex_ingester_tsdb_head_samples_appended_total` TSDB metric. #5952
 

pkg/ruler/api_test.go

@@ -337,15 +337,15 @@ func TestRuler_DeleteNamespace(t *testing.T) {
 
 	router.ServeHTTP(w, req)
 	require.Equal(t, http.StatusAccepted, w.Code)
-	require.Equal(t, "{\"status\":\"success\",\"data\":null,\"errorType\":\"\",\"error\":\"\"}", w.Body.String())
+	require.Equal(t, "{\"status\":\"success\",\"errorType\":\"\",\"error\":\"\"}", w.Body.String())
 
 	// On Partial failures
 	req = requestFor(t, http.MethodDelete, "https://localhost:8080/api/v1/rules/namespace2", nil, "user1")
 	w = httptest.NewRecorder()
 
 	router.ServeHTTP(w, req)
 	require.Equal(t, http.StatusInternalServerError, w.Code)
-	require.Equal(t, "{\"status\":\"error\",\"data\":null,\"errorType\":\"server_error\",\"error\":\"unable to delete rg\"}", w.Body.String())
+	require.Equal(t, "{\"status\":\"error\",\"errorType\":\"server_error\",\"error\":\"unable to delete rg\"}", w.Body.String())
 }
 
 func TestRuler_LimitsPerGroup(t *testing.T) {
@@ -430,7 +430,7 @@ rules:
 - record: up_rule
   expr: up{}
 `,
-			output: "{\"status\":\"success\",\"data\":null,\"errorType\":\"\",\"error\":\"\"}",
+			output: "{\"status\":\"success\",\"errorType\":\"\",\"error\":\"\"}",
 		},
 		{
 			name:   "when exceeding the rule group limit after sending the first group",
@@ -490,7 +490,7 @@ rules:
   expr: |2+
     up{}
 `,
-			output: "{\"status\":\"success\",\"data\":null,\"errorType\":\"\",\"error\":\"\"}",
+			output: "{\"status\":\"success\",\"errorType\":\"\",\"error\":\"\"}",
 		},
 		{
 			name:   "when pushing group that CANNOT be safely converted from RuleGroupDesc to RuleGroup yaml",

pkg/util/api/response.go

@@ -19,7 +19,7 @@ const (
 // Response defines the Prometheus response format.
 type Response struct {
 	Status    string       `json:"status"`
-	Data      interface{}  `json:"data"`
+	Data      interface{}  `json:"data,omitempty"`
 	ErrorType v1.ErrorType `json:"errorType"`
 	Error     string       `json:"error"`
 	Warnings  []string     `json:"warnings,omitempty"`