Alerting: Improve performance of matching captures

pkg/services/ngalert/eval/eval.go

@@ -302,14 +302,20 @@ type NumberValueCapture struct {
 }
 
 func queryDataResponseToExecutionResults(c models.Condition, execResp *backend.QueryDataResponse) ExecutionResults {
-	// eval captures for the '__value_string__' annotation and the Value property of the API response.
-	captures := make([]NumberValueCapture, 0, len(execResp.Responses))
-	captureVal := func(refID string, labels data.Labels, value *float64) {
-		captures = append(captures, NumberValueCapture{
+	// captures contains the values of all instant queries and expressions for each dimension
+	captures := make(map[string]map[data.Fingerprint]NumberValueCapture)
+	captureFn := func(refID string, labels data.Labels, value *float64) {
+		m := captures[refID]
+		if m == nil {
+			m = make(map[data.Fingerprint]NumberValueCapture)
+		}
+		fp := labels.Fingerprint()
+		m[fp] = NumberValueCapture{
 			Var:    refID,
 			Value:  value,
 			Labels: labels.Copy(),
-		})
+		}
+		captures[refID] = m
 	}
 
 	// datasourceUIDsForRefIDs is a short-lived lookup table of RefID to DatasourceUID
@@ -357,7 +363,7 @@ func queryDataResponseToExecutionResults(c models.Condition, execResp *backend.Q
 			if frame.Fields[0].Len() == 1 {
 				v = frame.At(0, 0).(*float64) // type checked above
 			}
-			captureVal(frame.RefID, frame.Fields[0].Labels, v)
+			captureFn(frame.RefID, frame.Fields[0].Labels, v)
 		}
 
 		if refID == c.Condition {
@@ -379,13 +385,27 @@ func queryDataResponseToExecutionResults(c models.Condition, execResp *backend.Q
 
 		if len(frame.Fields) == 1 {
 			theseLabels := frame.Fields[0].Labels
-			for _, cap := range captures {
-				// matching labels are equal labels, or when one set of labels includes the labels of the other.
-				if theseLabels.Equals(cap.Labels) || theseLabels.Contains(cap.Labels) || cap.Labels.Contains(theseLabels) {
+			fp := theseLabels.Fingerprint()
+
+			for _, fps := range captures {
+				// First look for a capture whose labels are an exact match
+				if v, ok := fps[fp]; ok {
 					if frame.Meta.Custom == nil {
 						frame.Meta.Custom = []NumberValueCapture{}
 					}
-					frame.Meta.Custom = append(frame.Meta.Custom.([]NumberValueCapture), cap)
+					frame.Meta.Custom = append(frame.Meta.Custom.([]NumberValueCapture), v)
+				} else {
+					// If no exact match was found, look for captures whose labels are either subsets
+					// or supersets
+					for _, v := range fps {
+						// matching labels are equal labels, or when one set of labels includes the labels of the other.
+						if theseLabels.Equals(v.Labels) || theseLabels.Contains(v.Labels) || v.Labels.Contains(theseLabels) {
+							if frame.Meta.Custom == nil {
+								frame.Meta.Custom = []NumberValueCapture{}
+							}
+							frame.Meta.Custom = append(frame.Meta.Custom.([]NumberValueCapture), v)
+						}
+					}
 				}
 			}
 		}

pkg/services/ngalert/eval/eval_bench_test.go

@@ -0,0 +1,59 @@
+package eval
+
+import (
+	"context"
+	"strconv"
+	"testing"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/backend"
+	"github.com/grafana/grafana-plugin-sdk-go/data"
+	"github.com/grafana/grafana/pkg/expr"
+	"github.com/grafana/grafana/pkg/services/ngalert/models"
+	"github.com/grafana/grafana/pkg/util"
+)
+
+func BenchmarkEvaluate(b *testing.B) {
+	var dataResp backend.QueryDataResponse
+	seedDataResponse(&dataResp, 10000)
+	var evaluator ConditionEvaluator = &conditionEvaluator{
+		expressionService: &fakeExpressionService{
+			hook: func(ctx context.Context, now time.Time, pipeline expr.DataPipeline) (*backend.QueryDataResponse, error) {
+				return &dataResp, nil
+			},
+		},
+		condition: models.Condition{
+			Condition: "B",
+		},
+	}
+	for i := 0; i < b.N; i++ {
+		_, err := evaluator.Evaluate(context.Background(), time.Now())
+		if err != nil {
+			b.Fatalf("Unexpected error: %s", err)
+		}
+	}
+}
+
+func seedDataResponse(r *backend.QueryDataResponse, n int) {
+	resps := make(backend.Responses, n)
+	for i := 0; i < n; i++ {
+		labels := data.Labels{
+			"foo": strconv.Itoa(i),
+			"bar": strconv.Itoa(i + 1),
+		}
+		a, b := resps["A"], resps["B"]
+		a.Frames = append(a.Frames, &data.Frame{
+			Fields: data.Fields{
+				data.NewField("Time", labels, []time.Time{time.Now()}),
+				data.NewField("Value", labels, []*float64{util.Pointer(1.0)}),
+			},
+		})
+		b.Frames = append(b.Frames, &data.Frame{
+			Fields: data.Fields{
+				data.NewField("Value", labels, []*float64{util.Pointer(1.0)}),
+			},
+		})
+		resps["A"], resps["B"] = a, b
+	}
+	r.Responses = resps
+}