SSE/Alerting: Support prom instant vector responses (#44865)

* SSE/Alerting: (Draft) Support prom instant vector responses
fixes #35663
* reduce\classic expressions to handle mathexp.Number
* use Notice for warning

Co-authored-by: Yuriy Tseretyan <yuriy.tseretyan@grafana.com>

pkg/expr/classic/classic.go

@@ -7,6 +7,7 @@ import (
 	"strconv"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
+
 	"github.com/grafana/grafana/pkg/expr/mathexp"
 )
 
@@ -99,13 +100,21 @@ func (ccc *ConditionsCmd) Execute(ctx context.Context, vars mathexp.Vars) (mathe
 		nilReducedCount := 0
 		firingCount := 0
 		for _, val := range querySeriesSet.Values {
-			series, ok := val.(mathexp.Series)
-			if !ok {
+			var reducedNum mathexp.Number
+			var name string
+			switch v := val.(type) {
+			case mathexp.Series:
+				reducedNum = c.Reducer.Reduce(v)
+				name = v.GetName()
+			case mathexp.Number:
+				reducedNum = v
+				if len(v.Frame.Fields) > 0 {
+					name = v.Frame.Fields[0].Name
+				}
+			default:
 				return newRes, fmt.Errorf("can only reduce type series, got type %v", val.Type())
 			}
 
-			reducedNum := c.Reducer.Reduce(series)
-
 			// TODO handle error / no data signals
 			thisCondNoDataFound := reducedNum.GetFloat64Value() == nil
 
@@ -118,7 +127,7 @@ func (ccc *ConditionsCmd) Execute(ctx context.Context, vars mathexp.Vars) (mathe
 			if evalRes {
 				match := EvalMatch{
 					Value:  reducedNum.GetFloat64Value(),
-					Metric: series.GetName(),
+					Metric: name,
 				}
 				if reducedNum.GetLabels() != nil {
 					match.Labels = reducedNum.GetLabels().Copy()

pkg/expr/classic/classic_test.go

@@ -6,9 +6,10 @@ import (
 	"testing"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
-	"github.com/grafana/grafana/pkg/expr/mathexp"
 	"github.com/stretchr/testify/require"
 	ptr "github.com/xorcare/pointer"
+
+	"github.com/grafana/grafana/pkg/expr/mathexp"
 )
 
 func TestUnmarshalConditionCMD(t *testing.T) {
@@ -346,6 +347,37 @@ func TestConditionsCmdExecute(t *testing.T) {
 				return v
 			},
 		},
+		{
+			name: "should accept numbers",
+			vars: mathexp.Vars{
+				"A": mathexp.Results{
+					Values: []mathexp.Value{
+						valBasedNumber(ptr.Float64(5)),
+						valBasedNumber(ptr.Float64(10)),
+						valBasedNumber(ptr.Float64(15)),
+					},
+				},
+			},
+			conditionsCmd: &ConditionsCmd{
+				Conditions: []condition{
+					{
+						QueryRefID: "A",
+						Reducer:    classicReducer("avg"),
+						Operator:   "and",
+						Evaluator:  &thresholdEvaluator{"gt", 1},
+					},
+				},
+			},
+			resultNumber: func() mathexp.Number {
+				v := valBasedNumber(ptr.Float64(1))
+				v.SetMeta([]EvalMatch{
+					{Value: ptr.Float64(5)},
+					{Value: ptr.Float64(10)},
+					{Value: ptr.Float64(15)},
+				})
+				return v
+			},
+		},
 	}
 
 	for _, tt := range tests {