rules: Support native histograms

Signed-off-by: Ganesh Vernekar <ganeshvern@gmail.com>

rules/manager.go

@@ -31,6 +31,7 @@ import (
 	"go.opentelemetry.io/otel/attribute"
 	"go.opentelemetry.io/otel/codes"
 
+	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/rulefmt"
 	"github.com/prometheus/prometheus/model/timestamp"
@@ -668,7 +669,16 @@ func (g *Group) Eval(ctx context.Context, ts time.Time) {
 			}()
 
 			for _, s := range vector {
-				if _, err := app.Append(0, s.Metric, s.T, s.V); err != nil {
+				if s.H != nil {
+					// We assume that all native histogram results are gauge histograms.
+					// TODO(codesome): once PromQL can give the counter reset info, remove this assumption.
+					s.H.CounterResetHint = histogram.GaugeType
+					_, err = app.AppendHistogram(0, s.Metric, s.T, nil, s.H)
+				} else {
+					_, err = app.Append(0, s.Metric, s.T, s.V)
+				}
+
+				if err != nil {
 					rule.SetHealth(HealthBad)
 					rule.SetLastError(err)
 					sp.SetStatus(codes.Error, err.Error())