From eabf3b9f731e03912428cc9f1a5b2d5290a1f63e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Philippe=20Qu=C3=A9m=C3=A9ner?=
 <JohnnyQQQQ@users.noreply.github.com>
Date: Thu, 12 Sep 2024 15:33:00 +0200
Subject: [PATCH] feat(alerting): add support for query service instant vectors
 (#92091)

---
 pkg/services/ngalert/eval/eval.go      | 62 ++++++++++++++++++--------
 pkg/services/ngalert/eval/eval_test.go | 46 +++++++++++++++++++
 2 files changed, 90 insertions(+), 18 deletions(-)

diff --git a/pkg/services/ngalert/eval/eval.go b/pkg/services/ngalert/eval/eval.go
index 548724ab0c8..0f0bf3074c1 100644
--- a/pkg/services/ngalert/eval/eval.go
+++ b/pkg/services/ngalert/eval/eval.go
@@ -15,7 +15,6 @@ import (
 
 	"github.com/grafana/grafana-plugin-sdk-go/backend"
 	"github.com/grafana/grafana-plugin-sdk-go/data"
-
 	"github.com/grafana/grafana/pkg/apimachinery/errutil"
 	"github.com/grafana/grafana/pkg/expr"
 	"github.com/grafana/grafana/pkg/expr/classic"
@@ -648,6 +647,9 @@ func datasourceUIDsToRefIDs(refIDsToDatasourceUIDs map[string]string) map[string
 // Each non-empty Frame must be a single Field of type []*float64 and of length 1.
 // Also, each Frame must be uniquely identified by its Field.Labels or a single Error result will be returned.
 //
+// An exception to this is data that is returned by the query service, which might have a timestamp and single value.
+// Those are handled with the appropriated logic.
+//
 // Per Frame, data becomes a State based on the following rules:
 //
 // If no value is set:
@@ -702,6 +704,13 @@ func evaluateExecutionResult(execResults ExecutionResults, ts time.Time) Results
 			continue
 		}
 
+		// The query service returns instant vectors from prometheus as scalars. We need to handle them accordingly.
+		if val, ok := scalarInstantVector(f); ok {
+			r := buildResult(f, val, ts)
+			evalResults = append(evalResults, r)
+			continue
+		}
+
 		if len(f.TypeIndices(data.FieldTypeTime, data.FieldTypeNullableTime)) > 0 {
 			appendErrRes(&invalidEvalResultFormatError{refID: f.RefID, reason: "looks like time series data, only reduced data can be alerted on."})
 			continue
@@ -734,23 +743,7 @@ func evaluateExecutionResult(execResults ExecutionResults, ts time.Time) Results
 		}
 
 		val := f.Fields[0].At(0).(*float64) // type checked by data.FieldTypeNullableFloat64 above
-
-		r := Result{
-			Instance:           f.Fields[0].Labels,
-			EvaluatedAt:        ts,
-			EvaluationDuration: time.Since(ts),
-			EvaluationString:   extractEvalString(f),
-			Values:             extractValues(f),
-		}
-
-		switch {
-		case val == nil:
-			r.State = NoData
-		case *val == 0:
-			r.State = Normal
-		default:
-			r.State = Alerting
-		}
+		r := buildResult(f, val, ts)
 
 		evalResults = append(evalResults, r)
 	}
@@ -776,6 +769,39 @@ func evaluateExecutionResult(execResults ExecutionResults, ts time.Time) Results
 	return evalResults
 }
 
+func buildResult(f *data.Frame, val *float64, ts time.Time) Result {
+	r := Result{
+		Instance:           f.Fields[0].Labels,
+		EvaluatedAt:        ts,
+		EvaluationDuration: time.Since(ts),
+		EvaluationString:   extractEvalString(f),
+		Values:             extractValues(f),
+	}
+	switch {
+	case val == nil:
+		r.State = NoData
+	case *val == 0:
+		r.State = Normal
+	default:
+		r.State = Alerting
+	}
+	return r
+}
+
+func scalarInstantVector(f *data.Frame) (*float64, bool) {
+	defaultReturnValue := 0.0
+	if len(f.Fields) != 2 {
+		return &defaultReturnValue, false
+	}
+	if f.Fields[0].Len() > 1 || (f.Fields[0].Type() != data.FieldTypeNullableTime && f.Fields[0].Type() != data.FieldTypeTime) {
+		return &defaultReturnValue, false
+	}
+	if f.Fields[1].Len() > 1 || f.Fields[1].Type() != data.FieldTypeNullableFloat64 {
+		return &defaultReturnValue, false
+	}
+	return f.Fields[1].At(0).(*float64), true
+}
+
 // AsDataFrame forms the EvalResults in Frame suitable for displaying in the table panel of the front end.
 // It displays one row per alert instance, with a column for each label and one for the alerting state.
 func (evalResults Results) AsDataFrame() data.Frame {
diff --git a/pkg/services/ngalert/eval/eval_test.go b/pkg/services/ngalert/eval/eval_test.go
index 6710737891b..f2cc7273ab9 100644
--- a/pkg/services/ngalert/eval/eval_test.go
+++ b/pkg/services/ngalert/eval/eval_test.go
@@ -62,6 +62,52 @@ func TestEvaluateExecutionResult(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "query service dataframe works as instant vector",
+			execResults: ExecutionResults{
+				Condition: func() []*data.Frame {
+					f := data.NewFrame("",
+						data.NewField("", nil, []*time.Time{util.Pointer(time.Now())}),
+						data.NewField("", nil, []*float64{util.Pointer(0.0)}),
+					)
+					f.Meta = &data.FrameMeta{
+						Custom: map[string]any{
+							"resultType": "scalar",
+						},
+					}
+					return []*data.Frame{f}
+				}(),
+			},
+			expectResultLength: 1,
+			expectResults: Results{
+				{
+					State: Normal,
+				},
+			},
+		},
+		{
+			desc: "query service dataframe works as instant vector when alerting",
+			execResults: ExecutionResults{
+				Condition: func() []*data.Frame {
+					f := data.NewFrame("",
+						data.NewField("", nil, []*time.Time{util.Pointer(time.Now())}),
+						data.NewField("", nil, []*float64{util.Pointer(1.0)}),
+					)
+					f.Meta = &data.FrameMeta{
+						Custom: map[string]any{
+							"resultType": "scalar",
+						},
+					}
+					return []*data.Frame{f}
+				}(),
+			},
+			expectResultLength: 1,
+			expectResults: Results{
+				{
+					State: Alerting,
+				},
+			},
+		},
 		{
 			desc: "nil value single instance is single a NoData state result",
 			execResults: ExecutionResults{