feat: Handle 409 status code returned by DELETE prepared_scale_down (#343)

* handle of 409 error

* add comment about callPrepareDownscaleAndReturnElapsedDurationsSinceInitiatedDownscale

Author: Segflow

pkg/controller/controller_test.go

@@ -941,6 +941,25 @@ func TestRolloutController_ReconcileStatefulsetWithDownscaleDelay(t *testing.T)
 				"DELETE http://ingester-zone-b-2.ingester-zone-b.test.svc.cluster.local./prepare-delayed-downscale",
 			},
 		},
+
+		"scale up succeeds even if DELETE returns 409 Conflict (i.e partition state locked)": {
+			statefulSets: []runtime.Object{
+				mockStatefulSet("ingester-zone-b", withReplicas(2, 2),
+					withMirrorReplicasAnnotations("test", customResourceGVK),
+					withDelayedDownscaleAnnotations(time.Hour, "http://pod/prepare-delayed-downscale")),
+			},
+			httpResponses: map[string]httpResponse{
+				"DELETE http://ingester-zone-b-0.ingester-zone-b.test.svc.cluster.local./prepare-delayed-downscale": {statusCode: http.StatusConflict, body: "partition state is locked"},
+				"DELETE http://ingester-zone-b-1.ingester-zone-b.test.svc.cluster.local./prepare-delayed-downscale": {statusCode: http.StatusConflict, body: "partition state is locked"},
+			},
+			customResourceScaleSpecReplicas:   5,
+			customResourceScaleStatusReplicas: 2,
+			expectedPatchedSets:               map[string][]string{"ingester-zone-b": {`{"spec":{"replicas":5}}`}},
+			expectedHttpRequests: []string{
+				"DELETE http://ingester-zone-b-0.ingester-zone-b.test.svc.cluster.local./prepare-delayed-downscale",
+				"DELETE http://ingester-zone-b-1.ingester-zone-b.test.svc.cluster.local./prepare-delayed-downscale",
+			},
+		},
 	}
 
 	for testName, testData := range tests {

pkg/controller/delay.go

@@ -200,6 +200,8 @@ func callPrepareDownscaleAndReturnElapsedDurationsSinceInitiatedDownscale(ctx co
 			}
 
 			if resp.StatusCode/100 != 2 {
+				// Unlike `callCancelDelayedDownscale`, here we consider all non 2xx status code as error and should block the downscale.
+				// this includes the case where we fail because a partition state change is locked.
 				level.Error(epLogger).Log("msg", "unexpected status code returned when calling POST on endpoint", "status", resp.StatusCode, "response_body", string(body))
 				return fmt.Errorf("HTTP POST request returned non-2xx status code: %v", resp.StatusCode)
 			}
@@ -260,8 +262,15 @@ func callCancelDelayedDownscale(ctx context.Context, logger log.Logger, client h
 			defer resp.Body.Close()
 
 			if resp.StatusCode/100 != 2 {
-				err := errors.New("HTTP DELETE request returned non-2xx status code")
 				body, readError := io.ReadAll(resp.Body)
+
+				// Handle 409 Conflict separately - this typically means that the partition state is locked by an engineer
+				if resp.StatusCode == http.StatusConflict {
+					level.Info(epLogger).Log("msg", "HTTP DELETE request returned 409 status code, delayed downscale cancellation skipped", "status", resp.StatusCode, "response_body", string(body))
+					return nil
+				}
+
+				err := errors.New("HTTP DELETE request returned non-2xx status code")
 				level.Error(epLogger).Log("msg", "unexpected status code returned when calling DELETE on endpoint", "status", resp.StatusCode, "response_body", string(body))
 				return errors.Join(err, readError)
 			}