Prometheus: Fix interpolating minStep for range queries when incremental querying enabled (#107715)

* return calculatedMinStep in first frame of the response

* update test files

* make the custom metadata as type of map[string]any

* append calculatedMinStep to custom metadata

* fix exemplar frame checking

packages/grafana-prometheus/src/querycache/QueryCache.test.ts

@@ -646,7 +646,7 @@ describe('QueryCache: Prometheus', function () {
 });
 
 describe('findDataPointStep', () => {
-  it('should interpolate custom interval', () => {
+  it('should interpolate custom interval when there is no calculatedMinStep in response', () => {
     const mockApplyInterpolation = jest.fn().mockImplementation(() => '1m');
     const req = mockPromRequest();
     req.targets[0].interval = '$interval';
@@ -654,4 +654,20 @@ describe('findDataPointStep', () => {
     findDatapointStep(req, respFrames, mockApplyInterpolation);
     expect(mockApplyInterpolation).toBeCalledTimes(1);
   });
+
+  it('should use the calculated minStep coming in response frame', () => {
+    const mockApplyInterpolation = jest.fn().mockImplementation(() => '1m');
+    const req = mockPromRequest();
+    // Cannot be interpolated on frontend as it was calculated on backend.
+    req.targets[0].interval = '$__rate_interval';
+    const respFrames = trimmedFirstPointInPromFrames as unknown as DataFrame[];
+    const expectedMinStep = 60000;
+    respFrames[0].meta = {
+      custom: {
+        calculatedMinStep: expectedMinStep,
+      },
+    };
+    const result = findDatapointStep(req, respFrames, mockApplyInterpolation);
+    expect(result).toBe(expectedMinStep);
+  });
 });

packages/grafana-prometheus/src/querycache/QueryCache.ts

@@ -282,7 +282,9 @@ export function findDatapointStep(
 
   let dataPointStep = request.intervalMs;
   if (target?.interval) {
-    const minStepMs = rangeUtil.intervalToMs(applyInterpolation(target.interval));
+    const minStepMs =
+      respFrames[0].meta?.custom?.['calculatedMinStep'] ??
+      rangeUtil.intervalToMs(applyInterpolation(target.interval, request.scopedVars));
     if (minStepMs > request.intervalMs) {
       dataPointStep = minStepMs;
     }

pkg/promlib/converter/prom.go

@@ -1140,8 +1140,8 @@ streamField:
 	return parsedLabelsMap, structuredMetadataMap, nil
 }
 
-func resultTypeToCustomMeta(resultType string) map[string]string {
-	return map[string]string{"resultType": resultType}
+func resultTypeToCustomMeta(resultType string) map[string]any {
+	return map[string]any{"resultType": resultType}
 }
 
 func timeFromFloat(fv float64) time.Time {

pkg/promlib/models/result.go

@@ -20,7 +20,7 @@ func ResultTypeFromFrame(frame *data.Frame) ResultType {
 	if frame.Meta.Custom == nil {
 		return ResultTypeUnknown
 	}
-	custom, ok := frame.Meta.Custom.(map[string]string)
+	custom, ok := frame.Meta.Custom.(map[string]any)
 	if !ok {
 		return ResultTypeUnknown
 	}

pkg/promlib/querydata/response.go

@@ -54,6 +54,14 @@ func (s *QueryData) parseResponse(ctx context.Context, q *models.Query, res *htt
 			addMetadataToMultiFrame(q, frame)
 			if i == 0 {
 				frame.Meta.ExecutedQueryString = executedQueryString(q)
+				if frame.Meta.Custom == nil {
+					frame.Meta.Custom = make(map[string]any)
+				}
+				if custom, ok := frame.Meta.Custom.(map[string]any); ok {
+					// This is required for incremental querying feature
+					// Knowing the calculated minStep is required for merging and caching the frames on frontend side
+					custom["calculatedMinStep"] = q.Step.Milliseconds()
+				}
 			}
 		}
 

pkg/promlib/testdata/range_auto.result.golden.jsonc

@@ -7,6 +7,7 @@
 //          1
 //      ],
 //      "custom": {
+//          "calculatedMinStep": 1000,
 //          "resultType": "matrix"
 //      },
 //      "executedQueryString": "Expr: histogram_quantile(0.95, sum(rate(tns_request_duration_seconds_bucket[4s])) by (le))\nStep: 1s"
@@ -44,6 +45,7 @@
             1
           ],
           "custom": {
+            "calculatedMinStep": 1000,
             "resultType": "matrix"
           },
           "executedQueryString": "Expr: histogram_quantile(0.95, sum(rate(tns_request_duration_seconds_bucket[4s])) by (le))\nStep: 1s"

pkg/promlib/testdata/range_infinity.result.golden.jsonc

@@ -7,6 +7,7 @@
 //          1
 //      ],
 //      "custom": {
+//          "calculatedMinStep": 1000,
 //          "resultType": "matrix"
 //      },
 //      "executedQueryString": "Expr: 1 / 0\nStep: 1s"
@@ -37,6 +38,7 @@
             1
           ],
           "custom": {
+            "calculatedMinStep": 1000,
             "resultType": "matrix"
           },
           "executedQueryString": "Expr: 1 / 0\nStep: 1s"

pkg/promlib/testdata/range_missing.result.golden.jsonc

@@ -7,6 +7,7 @@
 //          1
 //      ],
 //      "custom": {
+//          "calculatedMinStep": 1000,
 //          "resultType": "matrix"
 //      },
 //      "executedQueryString": "Expr: test1\nStep: 1s"
@@ -37,6 +38,7 @@
             1
           ],
           "custom": {
+            "calculatedMinStep": 1000,
             "resultType": "matrix"
           },
           "executedQueryString": "Expr: test1\nStep: 1s"

pkg/promlib/testdata/range_nan.result.golden.jsonc

@@ -7,6 +7,7 @@
 //          1
 //      ],
 //      "custom": {
+//          "calculatedMinStep": 1000,
 //          "resultType": "matrix"
 //      },
 //      "executedQueryString": "Expr: \nStep: 1s"
@@ -37,6 +38,7 @@
             1
           ],
           "custom": {
+            "calculatedMinStep": 1000,
             "resultType": "matrix"
           },
           "executedQueryString": "Expr: \nStep: 1s"

pkg/promlib/testdata/range_simple.result.golden.jsonc

@@ -7,6 +7,7 @@
 //          1
 //      ],
 //      "custom": {
+//          "calculatedMinStep": 1000,
 //          "resultType": "matrix"
 //      },
 //      "executedQueryString": "Expr: \nStep: 1s"
@@ -60,6 +61,7 @@
             1
           ],
           "custom": {
+            "calculatedMinStep": 1000,
             "resultType": "matrix"
           },
           "executedQueryString": "Expr: \nStep: 1s"