Add warnings for histogramRate applied with isCounter not matching counter/gauge histogram (#13392)

Add warnings for histogramRate applied with isCounter not matching counter/gauge histogram

---------

Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>

model/histogram/float_histogram.go

@@ -469,8 +469,8 @@ func (h *FloatHistogram) DetectReset(previous *FloatHistogram) bool {
 	// is a counter reset or not.
 	// We do the same if the CounterResetHint is GaugeType, which should not happen, but PromQL still
 	// allows the user to apply functions to gauge histograms that are only meant for counter histograms.
-	// In this case, we treat the gauge histograms as a counter histograms
-	// (and we plan to return a warning about it to the user).
+	// In this case, we treat the gauge histograms as counter histograms. A warning should be returned
+	// to the user in this case.
 	if h.Count < previous.Count {
 		return true
 	}

promql/functions.go

@@ -187,6 +187,8 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 		minSchema = last.Schema
 	}
 
+	var annos annotations.Annotations
+
 	// First iteration to find out two things:
 	// - What's the smallest relevant schema?
 	// - Are all data points histograms?
@@ -197,10 +199,12 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 		if curr == nil {
 			return nil, annotations.New().Add(annotations.NewMixedFloatsHistogramsWarning(metricName, pos))
 		}
-		// TODO(trevorwhitney): Check if isCounter is consistent with curr.CounterResetHint.
 		if !isCounter {
 			continue
 		}
+		if curr.CounterResetHint == histogram.GaugeType {
+			annos.Add(annotations.NewNativeHistogramNotCounterWarning(metricName, pos))
+		}
 		if curr.Schema < minSchema {
 			minSchema = curr.Schema
 		}
@@ -218,6 +222,8 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 			}
 			prev = curr
 		}
+	} else if points[0].H.CounterResetHint != histogram.GaugeType || points[len(points)-1].H.CounterResetHint != histogram.GaugeType {
+		annos.Add(annotations.NewNativeHistogramNotGaugeWarning(metricName, pos))
 	}
 
 	h.CounterResetHint = histogram.GaugeType

util/annotations/annotations.go

@@ -107,6 +107,8 @@ var (
 	BadBucketLabelWarning               = fmt.Errorf("%w: bucket label %q is missing or has a malformed value", PromQLWarning, model.BucketLabel)
 	MixedFloatsHistogramsWarning        = fmt.Errorf("%w: encountered a mix of histograms and floats for metric name", PromQLWarning)
 	MixedClassicNativeHistogramsWarning = fmt.Errorf("%w: vector contains a mix of classic and native histograms for metric name", PromQLWarning)
+	NativeHistogramNotCounterWarning    = fmt.Errorf("%w: this native histogram metric is not a counter:", PromQLWarning)
+	NativeHistogramNotGaugeWarning      = fmt.Errorf("%w: this native histogram metric is not a gauge:", PromQLWarning)
 
 	PossibleNonCounterInfo                  = fmt.Errorf("%w: metric might not be a counter, name does not end in _total/_sum/_count/_bucket:", PromQLInfo)
 	HistogramQuantileForcedMonotonicityInfo = fmt.Errorf("%w: input to histogram_quantile needed to be fixed for monotonicity (see https://prometheus.io/docs/prometheus/latest/querying/functions/#histogram_quantile) for metric name", PromQLInfo)
@@ -166,6 +168,24 @@ func NewMixedClassicNativeHistogramsWarning(metricName string, pos posrange.Posi
 	}
 }
 
+// NewNativeHistogramNotCounterWarning is used when histogramRate is called
+// with isCounter set to true on a gauge histogram.
+func NewNativeHistogramNotCounterWarning(metricName string, pos posrange.PositionRange) error {
+	return annoErr{
+		PositionRange: pos,
+		Err:           fmt.Errorf("%w %q", NativeHistogramNotCounterWarning, metricName),
+	}
+}
+
+// NewNativeHistogramNotGaugeWarning is used when histogramRate is called
+// with isCounter set to false on a counter histogram.
+func NewNativeHistogramNotGaugeWarning(metricName string, pos posrange.PositionRange) error {
+	return annoErr{
+		PositionRange: pos,
+		Err:           fmt.Errorf("%w %q", NativeHistogramNotGaugeWarning, metricName),
+	}
+}
+
 // NewPossibleNonCounterInfo is used when a named counter metric with only float samples does not
 // have the suffixes _total, _sum, _count, or _bucket.
 func NewPossibleNonCounterInfo(metricName string, pos posrange.PositionRange) error {