Histograms: set annotation when adding or subtracting histograms that have `not_reset` and `reset` hints.

Signed-off-by: Julius Hinze <julius.hinze@grafana.com>

model/histogram/float_histogram.go

@@ -336,15 +336,18 @@ func (h *FloatHistogram) Div(scalar float64) *FloatHistogram {
 // The method reconciles differences in the zero threshold and in the schema, and
 // changes them if needed. The other histogram will not be modified in any case.
 // Adding is currently only supported between 2 exponential histograms, or between
-// 2 custom buckets histograms with the exact same custom bounds.
+// 2 custom buckets histograms with the exact same custom bounds. If CounterResetHint
+// values conflict, the receiver's hint is set to unknown, and counterResetCollision
+// is returned as true. A counter reset conflict occurs iff one of two histograms indicate
+// a counter reset (CounterReset) while the other indicates no reset (NotCounterReset).
 //
 // This method returns a pointer to the receiving histogram for convenience.
-func (h *FloatHistogram) Add(other *FloatHistogram) (*FloatHistogram, error) {
+func (h *FloatHistogram) Add(other *FloatHistogram) (res *FloatHistogram, counterResetCollision bool, err error) {
 	if h.UsesCustomBuckets() != other.UsesCustomBuckets() {
-		return nil, ErrHistogramsIncompatibleSchema
+		return nil, false, ErrHistogramsIncompatibleSchema
 	}
 	if h.UsesCustomBuckets() && !FloatBucketsMatch(h.CustomValues, other.CustomValues) {
-		return nil, ErrHistogramsIncompatibleBounds
+		return nil, false, ErrHistogramsIncompatibleBounds
 	}
 
 	switch {
@@ -368,7 +371,7 @@ func (h *FloatHistogram) Add(other *FloatHistogram) (*FloatHistogram, error) {
 		// They are a direct collision of CounterReset and NotCounterReset.
 		// Conservatively set the CounterResetHint to "unknown" and issue a warning.
 		h.CounterResetHint = UnknownCounterReset
-		// TODO(trevorwhitney): Actually issue the warning as soon as the plumbing for it is in place
+		counterResetCollision = true
 	}
 
 	if !h.UsesCustomBuckets() {
@@ -387,7 +390,7 @@ func (h *FloatHistogram) Add(other *FloatHistogram) (*FloatHistogram, error) {
 
 	if h.UsesCustomBuckets() {
 		h.PositiveSpans, h.PositiveBuckets = addBuckets(h.Schema, h.ZeroThreshold, false, hPositiveSpans, hPositiveBuckets, otherPositiveSpans, otherPositiveBuckets)
-		return h, nil
+		return h, counterResetCollision, nil
 	}
 
 	var (
@@ -411,19 +414,20 @@ func (h *FloatHistogram) Add(other *FloatHistogram) (*FloatHistogram, error) {
 	h.PositiveSpans, h.PositiveBuckets = addBuckets(h.Schema, h.ZeroThreshold, false, hPositiveSpans, hPositiveBuckets, otherPositiveSpans, otherPositiveBuckets)
 	h.NegativeSpans, h.NegativeBuckets = addBuckets(h.Schema, h.ZeroThreshold, false, hNegativeSpans, hNegativeBuckets, otherNegativeSpans, otherNegativeBuckets)
 
-	return h, nil
+	return h, counterResetCollision, nil
 }
 
 // Sub works like Add but subtracts the other histogram.
-func (h *FloatHistogram) Sub(other *FloatHistogram) (*FloatHistogram, error) {
+func (h *FloatHistogram) Sub(other *FloatHistogram) (res *FloatHistogram, counterResetCollision bool, err error) {
 	if h.UsesCustomBuckets() != other.UsesCustomBuckets() {
-		return nil, ErrHistogramsIncompatibleSchema
+		return nil, false, ErrHistogramsIncompatibleSchema
 	}
 	if h.UsesCustomBuckets() && !FloatBucketsMatch(h.CustomValues, other.CustomValues) {
-		return nil, ErrHistogramsIncompatibleBounds
+		return nil, false, ErrHistogramsIncompatibleBounds
 	}
 
-	// Prevent counter resets when subtracting as this might decrease counters.
+	counterResetCollision = hasCounterResetCollision(h, other)
+
 	h.CounterResetHint = GaugeType
 
 	if !h.UsesCustomBuckets() {
@@ -442,7 +446,7 @@ func (h *FloatHistogram) Sub(other *FloatHistogram) (*FloatHistogram, error) {
 
 	if h.UsesCustomBuckets() {
 		h.PositiveSpans, h.PositiveBuckets = addBuckets(h.Schema, h.ZeroThreshold, true, hPositiveSpans, hPositiveBuckets, otherPositiveSpans, otherPositiveBuckets)
-		return h, nil
+		return h, counterResetCollision, nil
 	}
 
 	var (
@@ -465,7 +469,14 @@ func (h *FloatHistogram) Sub(other *FloatHistogram) (*FloatHistogram, error) {
 	h.PositiveSpans, h.PositiveBuckets = addBuckets(h.Schema, h.ZeroThreshold, true, hPositiveSpans, hPositiveBuckets, otherPositiveSpans, otherPositiveBuckets)
 	h.NegativeSpans, h.NegativeBuckets = addBuckets(h.Schema, h.ZeroThreshold, true, hNegativeSpans, hNegativeBuckets, otherNegativeSpans, otherNegativeBuckets)
 
-	return h, nil
+	return h, counterResetCollision, nil
+}
+
+// hasCounterResetCollision returns true iff one of two histogram indicates
+// a counter reset (CounterReset) while the other indicates no reset (NotCounterReset).
+func hasCounterResetCollision(a, b *FloatHistogram) bool {
+	return a.CounterResetHint == CounterReset && b.CounterResetHint == NotCounterReset ||
+		a.CounterResetHint == NotCounterReset && b.CounterResetHint == CounterReset
 }
 
 // Equals returns true if the given float histogram matches exactly.

model/histogram/float_histogram_test.go

@@ -1648,10 +1648,11 @@ func TestFloatHistogramAdd(t *testing.T) {
 		name                     string
 		in1, in2, expected       *FloatHistogram
 		expErrMsg                string
+		expCounterResetCollision bool
 	}{
 		{
-			"same bucket layout",
+			name: "same bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1661,7 +1662,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1671,7 +1672,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1681,11 +1682,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{4, 2, 9, 10},
 			},
-			"",
 		},
 		{
-			"same bucket layout, defined differently",
+			name: "same bucket layout, defined differently",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1695,7 +1695,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1705,7 +1705,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 7}},
 				NegativeBuckets: []float64{1, 1, 0, 0, 0, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1715,11 +1715,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 5}, {0, 2}},
 				NegativeBuckets: []float64{4, 2, 0, 0, 0, 9, 10},
 			},
-			"",
 		},
 		{
-			"non-overlapping spans",
+			name: "non-overlapping spans",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.001,
 				ZeroCount:       11,
 				Count:           30,
@@ -1729,7 +1728,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.001,
 				ZeroCount:       8,
 				Count:           21,
@@ -1739,7 +1738,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{-9, 2}, {3, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.001,
 				ZeroCount:       19,
 				Count:           51,
@@ -1749,11 +1748,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{-9, 2}, {3, 2}, {5, 2}, {3, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4, 3, 1, 5, 6},
 			},
-			"",
 		},
 		{
-			"non-overlapping spans inverted order",
+			name: "non-overlapping spans inverted order",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1763,7 +1761,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{-6, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1773,7 +1771,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1783,11 +1781,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{-6, 2}, {1, 2}, {4, 2}, {3, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4, 3, 1, 5, 6},
 			},
-			"",
 		},
 		{
-			"overlapping spans",
+			name: "overlapping spans",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1797,7 +1794,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1807,7 +1804,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1817,11 +1814,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"overlapping spans inverted order",
+			name: "overlapping spans inverted order",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1831,7 +1827,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1841,7 +1837,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1851,11 +1847,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"schema change",
+			name: "schema change",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -1866,7 +1861,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1877,7 +1872,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{6, 3}, {6, 4}},
 				NegativeBuckets: []float64{3, 0.5, 0.5, 2, 3, 2, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       19,
 				Count:           51,
@@ -1887,11 +1882,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"larger zero bucket in first histogram",
+			name: "larger zero bucket in first histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   1,
 				ZeroCount:       17,
 				Count:           21,
@@ -1901,7 +1895,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1911,7 +1905,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   1,
 				ZeroCount:       29,
 				Count:           51,
@@ -1921,11 +1915,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"larger zero bucket in second histogram",
+			name: "larger zero bucket in second histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1935,7 +1928,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   1,
 				ZeroCount:       17,
 				Count:           21,
@@ -1945,7 +1938,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   1,
 				ZeroCount:       29,
 				Count:           51,
@@ -1955,11 +1948,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"larger zero threshold in first histogram ends up inside a populated bucket of second histogram",
+			name: "larger zero threshold in first histogram ends up inside a populated bucket of second histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.2,
 				ZeroCount:       17,
 				Count:           21,
@@ -1969,7 +1961,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -1979,7 +1971,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       29,
 				Count:           51,
@@ -1989,11 +1981,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"larger zero threshold in second histogram ends up inside a populated bucket of first histogram",
+			name: "larger zero threshold in second histogram ends up inside a populated bucket of first histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -2003,7 +1994,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.2,
 				ZeroCount:       17,
 				Count:           21,
@@ -2013,7 +2004,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       29,
 				Count:           51,
@@ -2023,11 +2014,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"schema change combined with larger zero bucket in second histogram",
+			name: "schema change combined with larger zero bucket in second histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -2038,7 +2028,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       12,
 				Count:           30,
@@ -2049,7 +2039,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{6, 3}, {6, 4}},
 				NegativeBuckets: []float64{3, 0.5, 0.5, 2, 3, 2, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       22,
 				Count:           51,
@@ -2059,11 +2049,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"schema change combined with larger zero bucket in first histogram",
+			name: "schema change combined with larger zero bucket in first histogram",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       8,
 				Count:           21,
@@ -2074,7 +2063,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{4, 2}, {1, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -2085,7 +2074,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{6, 3}, {6, 4}},
 				NegativeBuckets: []float64{3, 0.5, 0.5, 2, 3, 2, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:   0.25,
 				ZeroCount:       20,
 				Count:           51,
@@ -2095,11 +2084,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{3, 2, 1, 4, 9, 6},
 			},
-			"",
 		},
 		{
-			"same custom bucket layout",
+			name: "same custom bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2107,7 +2095,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             1.234,
@@ -2115,7 +2103,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           26,
 				Sum:             3.579,
@@ -2123,11 +2111,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 5, 7, 13},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"same custom bucket layout, defined differently",
+			name: "same custom bucket layout, defined differently",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2135,7 +2122,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             1.234,
@@ -2143,7 +2130,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           26,
 				Sum:             3.579,
@@ -2151,11 +2138,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 5, 7, 13},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"non-overlapping spans with custom buckets",
+			name: "non-overlapping spans with custom buckets",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2163,7 +2149,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           20,
 				Sum:             1.234,
@@ -2171,7 +2157,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{5, 4, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           35,
 				Sum:             3.579,
@@ -2179,11 +2165,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 5, 4, 3, 4, 7, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"non-overlapping spans inverted order with custom buckets",
+			name: "non-overlapping spans inverted order with custom buckets",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           20,
 				Sum:             1.234,
@@ -2191,7 +2176,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{5, 4, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2199,7 +2184,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           35,
 				Sum:             3.579,
@@ -2207,11 +2192,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 5, 4, 3, 4, 7, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"overlapping spans with custom buckets",
+			name: "overlapping spans with custom buckets",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2219,7 +2203,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           27,
 				Sum:             1.234,
@@ -2227,7 +2211,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{5, 4, 2, 3, 6, 2, 5},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           42,
 				Sum:             3.579,
@@ -2235,11 +2219,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 5, 4, 2, 6, 10, 9, 5},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"overlapping spans inverted order with custom buckets",
+			name: "overlapping spans inverted order with custom buckets",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           27,
 				Sum:             1.234,
@@ -2247,7 +2230,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{5, 4, 2, 3, 6, 2, 5},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2255,7 +2238,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           42,
 				Sum:             3.579,
@@ -2263,11 +2246,10 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 5, 4, 2, 6, 10, 9, 5},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			"",
 		},
 		{
-			"different custom bucket layout",
+			name: "different custom bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             2.345,
@@ -2275,7 +2257,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             1.234,
@@ -2283,12 +2265,11 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4, 5},
 			},
-			nil,
+			expErrMsg: "cannot apply this operation on custom buckets histograms with different custom bounds",
-			"cannot apply this operation on custom buckets histograms with different custom bounds",
 		},
 		{
-			"mix exponential and custom buckets histograms",
+			name: "mix exponential and custom buckets histograms",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           59,
@@ -2299,7 +2280,7 @@ func TestFloatHistogramAdd(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{4, 10, 1, 4, 14, 7},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             12,
@@ -2307,20 +2288,32 @@ func TestFloatHistogramAdd(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			nil,
+			expErrMsg: "cannot apply this operation on histograms with a mix of exponential and custom bucket schemas",
-			"cannot apply this operation on histograms with a mix of exponential and custom bucket schemas",
+		},
+		{
+			name: "warn on counter reset hint collision",
+			in1: &FloatHistogram{
+				Schema:           CustomBucketsSchema,
+				CounterResetHint: CounterReset,
+			},
+			in2: &FloatHistogram{
+				Schema:           CustomBucketsSchema,
+				CounterResetHint: NotCounterReset,
+			},
+			expErrMsg:                "",
+			expCounterResetCollision: true,
 		},
 	}
 
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			testHistogramAdd(t, c.in1, c.in2, c.expected, c.expErrMsg)
+			testHistogramAdd(t, c.in1, c.in2, c.expected, c.expErrMsg, c.expCounterResetCollision)
-			testHistogramAdd(t, c.in2, c.in1, c.expected, c.expErrMsg)
+			testHistogramAdd(t, c.in2, c.in1, c.expected, c.expErrMsg, c.expCounterResetCollision)
 		})
 	}
 }
 
-func testHistogramAdd(t *testing.T, a, b, expected *FloatHistogram, expErrMsg string) {
+func testHistogramAdd(t *testing.T, a, b, expected *FloatHistogram, expErrMsg string, expCounterResetCollision bool) {
 	var (
 		aCopy        = a.Copy()
 		bCopy        = b.Copy()
@@ -2331,13 +2324,16 @@ func testHistogramAdd(t *testing.T, a, b, expected *FloatHistogram, expErrMsg st
 		expectedCopy = expected.Copy()
 	}
 
-	res, err := aCopy.Add(bCopy)
+	res, warn, err := aCopy.Add(bCopy)
 	if expErrMsg != "" {
 		require.EqualError(t, err, expErrMsg)
 	} else {
 		require.NoError(t, err)
 	}
 
+	// Check that the warnings are correct.
+	require.Equal(t, expCounterResetCollision, warn)
+
 	if expected != nil {
 		res.Compact(0)
 		expectedCopy.Compact(0)
@@ -2359,10 +2355,11 @@ func TestFloatHistogramSub(t *testing.T) {
 		name                     string
 		in1, in2, expected       *FloatHistogram
 		expErrMsg                string
+		expCounterResetCollision bool
 	}{
 		{
-			"same bucket layout",
+			name: "same bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       11,
 				Count:           30,
@@ -2372,7 +2369,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{3, 1, 5, 6},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           21,
@@ -2382,7 +2379,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeSpans:   []Span{{3, 2}, {3, 2}},
 				NegativeBuckets: []float64{1, 1, 4, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:    0.01,
 				ZeroCount:        3,
 				Count:            9,
@@ -2393,11 +2390,10 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeBuckets:  []float64{2, 0, 1, 2},
 				CounterResetHint: GaugeType,
 			},
-			"",
 		},
 		{
-			"schema change",
+			name: "schema change",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           59,
@@ -2408,7 +2404,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{4, 10, 1, 4, 14, 7},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       2,
 				Count:           19,
@@ -2419,7 +2415,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeSpans:   []Span{{6, 3}, {6, 4}},
 				NegativeBuckets: []float64{3, 0.5, 0.5, 2, 3, 2, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				ZeroThreshold:    0.01,
 				ZeroCount:        6,
 				Count:            40,
@@ -2430,11 +2426,10 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeBuckets:  []float64{1, 9, 1, 4, 9, 1},
 				CounterResetHint: GaugeType,
 			},
-			"",
 		},
 		{
-			"same custom bucket layout",
+			name: "same custom bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             23,
@@ -2442,7 +2437,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             12,
@@ -2450,7 +2445,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			expected: &FloatHistogram{
 				Schema:           CustomBucketsSchema,
 				Count:            4,
 				Sum:              11,
@@ -2459,11 +2454,10 @@ func TestFloatHistogramSub(t *testing.T) {
 				CustomValues:     []float64{1, 2, 3, 4},
 				CounterResetHint: GaugeType,
 			},
-			"",
 		},
 		{
-			"different custom bucket layout",
+			name: "different custom bucket layout",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           15,
 				Sum:             23,
@@ -2471,7 +2465,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				PositiveBuckets: []float64{1, 0, 3, 4, 7},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             12,
@@ -2479,12 +2473,11 @@ func TestFloatHistogramSub(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4, 5},
 			},
-			nil,
+			expErrMsg: "cannot apply this operation on custom buckets histograms with different custom bounds",
-			"cannot apply this operation on custom buckets histograms with different custom bounds",
 		},
 		{
-			"mix exponential and custom buckets histograms",
+			name: "mix exponential and custom buckets histograms",
-			&FloatHistogram{
+			in1: &FloatHistogram{
 				ZeroThreshold:   0.01,
 				ZeroCount:       8,
 				Count:           59,
@@ -2495,7 +2488,7 @@ func TestFloatHistogramSub(t *testing.T) {
 				NegativeSpans:   []Span{{3, 3}, {1, 3}},
 				NegativeBuckets: []float64{4, 10, 1, 4, 14, 7},
 			},
-			&FloatHistogram{
+			in2: &FloatHistogram{
 				Schema:          CustomBucketsSchema,
 				Count:           11,
 				Sum:             12,
@@ -2503,25 +2496,37 @@ func TestFloatHistogramSub(t *testing.T) {
 				PositiveBuckets: []float64{0, 0, 2, 3, 6},
 				CustomValues:    []float64{1, 2, 3, 4},
 			},
-			nil,
+			expErrMsg: "cannot apply this operation on histograms with a mix of exponential and custom bucket schemas",
-			"cannot apply this operation on histograms with a mix of exponential and custom bucket schemas",
+		},
+		{
+			name: "warn on counter reset hint collision",
+			in1: &FloatHistogram{
+				Schema:           CustomBucketsSchema,
+				CounterResetHint: CounterReset,
+			},
+			in2: &FloatHistogram{
+				Schema:           CustomBucketsSchema,
+				CounterResetHint: NotCounterReset,
+			},
+			expErrMsg:                "",
+			expCounterResetCollision: true,
 		},
 	}
 
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {
-			testFloatHistogramSub(t, c.in1, c.in2, c.expected, c.expErrMsg)
+			testFloatHistogramSub(t, c.in1, c.in2, c.expected, c.expErrMsg, c.expCounterResetCollision)
 
 			var expectedNegative *FloatHistogram
 			if c.expected != nil {
 				expectedNegative = c.expected.Copy().Mul(-1)
 			}
-			testFloatHistogramSub(t, c.in2, c.in1, expectedNegative, c.expErrMsg)
+			testFloatHistogramSub(t, c.in2, c.in1, expectedNegative, c.expErrMsg, c.expCounterResetCollision)
 		})
 	}
 }
 
-func testFloatHistogramSub(t *testing.T, a, b, expected *FloatHistogram, expErrMsg string) {
+func testFloatHistogramSub(t *testing.T, a, b, expected *FloatHistogram, expErrMsg string, expCounterResetCollision bool) {
 	var (
 		aCopy        = a.Copy()
 		bCopy        = b.Copy()
@@ -2532,7 +2537,7 @@ func testFloatHistogramSub(t *testing.T, a, b, expected *FloatHistogram, expErrM
 		expectedCopy = expected.Copy()
 	}
 
-	res, err := aCopy.Sub(bCopy)
+	res, warn, err := aCopy.Sub(bCopy)
 	if expErrMsg != "" {
 		require.EqualError(t, err, expErrMsg)
 	} else {
@@ -2550,6 +2555,9 @@ func testFloatHistogramSub(t *testing.T, a, b, expected *FloatHistogram, expErrM
 
 		// Check that the argument was not mutated.
 		require.Equal(t, b, bCopy)
+
+		// Check that the warnings are correct.
+		require.Equal(t, expCounterResetCollision, warn)
 	}
 }
 

promql/engine.go

@@ -2830,7 +2830,7 @@ func (ev *evaluator) VectorscalarBinop(op parser.ItemType, lhs Vector, rhs Scala
 			lh, rh = rh, lh
 		}
 		float, histogram, keep, err := vectorElemBinop(op, lf, rf, lh, rh, pos)
-		if err != nil {
+		if err != nil && !errors.Is(err, annotations.PromQLWarning) {
 			lastErr = err
 			continue
 		}
@@ -2955,17 +2955,23 @@ func vectorElemBinop(op parser.ItemType, lhs, rhs float64, hlhs, hrhs *histogram
 		{
 			switch op {
 			case parser.ADD:
-				res, err := hlhs.Copy().Add(hrhs)
+				res, counterResetCollision, err := hlhs.Copy().Add(hrhs)
 				if err != nil {
 					return 0, nil, false, err
 				}
-				return 0, res.Compact(0), true, nil
+				if counterResetCollision {
+					err = annotations.NewHistogramCounterResetCollisionWarning(pos)
+				}
+				return 0, res.Compact(0), true, err
 			case parser.SUB:
-				res, err := hlhs.Copy().Sub(hrhs)
+				res, counterResetCollision, err := hlhs.Copy().Sub(hrhs)
 				if err != nil {
 					return 0, nil, false, err
 				}
-				return 0, res.Compact(0), true, nil
+				if counterResetCollision {
+					err = annotations.NewHistogramCounterResetCollisionWarning(pos)
+				}
+				return 0, res.Compact(0), true, err
 			case parser.EQLC:
 				// This operation expects that both histograms are compacted.
 				return 0, hlhs, hlhs.Equals(hrhs), nil
@@ -3078,7 +3084,7 @@ func (ev *evaluator) aggregation(e *parser.AggregateExpr, q float64, inputMatrix
 			if h != nil {
 				group.hasHistogram = true
 				if group.histogramValue != nil {
-					_, err := group.histogramValue.Add(h)
+					_, _, err := group.histogramValue.Add(h)
 					if err != nil {
 						handleAggregationError(err, e, inputMatrix[si].Metric.Get(model.MetricNameLabel), &annos)
 						group.incompatibleHistograms = true
@@ -3131,13 +3137,13 @@ func (ev *evaluator) aggregation(e *parser.AggregateExpr, q float64, inputMatrix
 				if group.histogramValue != nil {
 					left := h.Copy().Div(group.groupCount)
 					right := group.histogramValue.Copy().Div(group.groupCount)
-					toAdd, err := left.Sub(right)
+					toAdd, _, err := left.Sub(right)
 					if err != nil {
 						handleAggregationError(err, e, inputMatrix[si].Metric.Get(model.MetricNameLabel), &annos)
 						group.incompatibleHistograms = true
 						continue
 					}
-					_, err = group.histogramValue.Add(toAdd)
+					_, _, err = group.histogramValue.Add(toAdd)
 					if err != nil {
 						handleAggregationError(err, e, inputMatrix[si].Metric.Get(model.MetricNameLabel), &annos)
 						group.incompatibleHistograms = true

promql/engine_internal_test.go

@@ -21,7 +21,9 @@ import (
 	"github.com/prometheus/common/promslog"
 	"github.com/stretchr/testify/require"
 
+	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/promql/parser"
+	"github.com/prometheus/prometheus/promql/parser/posrange"
 	"github.com/prometheus/prometheus/util/annotations"
 )
 
@@ -77,3 +79,65 @@ func TestRecoverEvaluatorErrorWithWarnings(t *testing.T) {
 
 	panic(e)
 }
+
+func TestVectorElemBinop_Histograms(t *testing.T) {
+	testCases := []struct {
+		name       string
+		op         parser.ItemType
+		hlhs, hrhs *histogram.FloatHistogram
+		want       *histogram.FloatHistogram
+		wantErr    error
+	}{
+		{
+			name: "ADD with unknown counter reset hints",
+			op:   parser.ADD,
+			hlhs: &histogram.FloatHistogram{},
+			hrhs: &histogram.FloatHistogram{},
+			want: &histogram.FloatHistogram{},
+		},
+		{
+			name: "ADD with mixed counter reset hints",
+			op:   parser.ADD,
+			hlhs: &histogram.FloatHistogram{
+				CounterResetHint: histogram.CounterReset,
+			},
+			hrhs: &histogram.FloatHistogram{
+				CounterResetHint: histogram.NotCounterReset,
+			},
+			want:    &histogram.FloatHistogram{},
+			wantErr: annotations.HistogramCounterResetCollisionWarning,
+		},
+		{
+			name: "SUB with unknown counter reset hints",
+			op:   parser.SUB,
+			hlhs: &histogram.FloatHistogram{},
+			hrhs: &histogram.FloatHistogram{},
+			want: &histogram.FloatHistogram{
+				CounterResetHint: histogram.GaugeType,
+			},
+		},
+		{
+			name: "SUB with mixed counter reset hints",
+			op:   parser.SUB,
+			hlhs: &histogram.FloatHistogram{
+				CounterResetHint: histogram.CounterReset,
+			},
+			hrhs: &histogram.FloatHistogram{
+				CounterResetHint: histogram.NotCounterReset,
+			},
+			want:    &histogram.FloatHistogram{},
+			wantErr: annotations.HistogramCounterResetCollisionWarning,
+		},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			_, got, _, err := vectorElemBinop(tc.op, 0, 0, tc.hlhs, tc.hrhs, posrange.PositionRange{})
+			if tc.wantErr != nil {
+				require.ErrorIs(t, err, tc.wantErr)
+				return
+			}
+			require.NoError(t, err)
+			require.Equal(t, tc.want, got)
+		})
+	}
+}

promql/functions.go

@@ -254,7 +254,7 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 	}
 
 	h := last.CopyToSchema(minSchema)
-	_, err := h.Sub(prev)
+	_, counterResetCollision, err := h.Sub(prev)
 	if err != nil {
 		if errors.Is(err, histogram.ErrHistogramsIncompatibleSchema) {
 			return nil, annotations.New().Add(annotations.NewMixedExponentialCustomHistogramsWarning(metricName, pos))
@@ -263,12 +263,16 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 		}
 	}
 
+	if counterResetCollision {
+		annos.Add(annotations.NewHistogramCounterResetCollisionWarning(pos))
+	}
+
 	if isCounter {
 		// Second iteration to deal with counter resets.
 		for _, currPoint := range points[1:] {
 			curr := currPoint.H
 			if curr.DetectReset(prev) {
-				_, err := h.Add(prev)
+				_, counterResetCollision, err := h.Add(prev)
 				if err != nil {
 					if errors.Is(err, histogram.ErrHistogramsIncompatibleSchema) {
 						return nil, annotations.New().Add(annotations.NewMixedExponentialCustomHistogramsWarning(metricName, pos))
@@ -276,6 +280,9 @@ func histogramRate(points []HPoint, isCounter bool, metricName string, pos posra
 						return nil, annotations.New().Add(annotations.NewIncompatibleCustomBucketsHistogramsWarning(metricName, pos))
 					}
 				}
+				if counterResetCollision {
+					annos.Add(annotations.NewHistogramCounterResetCollisionWarning(pos))
+				}
 			}
 			prev = curr
 		}
@@ -389,12 +396,15 @@ func instantValue(vals Matrix, args parser.Expressions, out Vector, isRate bool)
 			annos.Add(annotations.NewNativeHistogramNotGaugeWarning(metricName, args.PositionRange()))
 		}
 		if !isRate || !ss[1].H.DetectReset(ss[0].H) {
-			_, err := resultSample.H.Sub(ss[0].H)
+			_, counterResetCollision, err := resultSample.H.Sub(ss[0].H)
 			if errors.Is(err, histogram.ErrHistogramsIncompatibleSchema) {
 				return out, annos.Add(annotations.NewMixedExponentialCustomHistogramsWarning(metricName, args.PositionRange()))
 			} else if errors.Is(err, histogram.ErrHistogramsIncompatibleBounds) {
 				return out, annos.Add(annotations.NewIncompatibleCustomBucketsHistogramsWarning(metricName, args.PositionRange()))
 			}
+			if counterResetCollision {
+				annos.Add(annotations.NewHistogramCounterResetCollisionWarning(args.PositionRange()))
+			}
 		}
 		resultSample.H.CounterResetHint = histogram.GaugeType
 		resultSample.H.Compact(0)
@@ -699,20 +709,27 @@ func funcAvgOverTime(_ []Vector, matrixVal Matrix, args parser.Expressions, enh
 	// the current implementation is accurate enough for practical purposes.
 	if len(firstSeries.Floats) == 0 {
 		// The passed values only contain histograms.
+		var annos annotations.Annotations
 		vec, err := aggrHistOverTime(matrixVal, enh, func(s Series) (*histogram.FloatHistogram, error) {
 			mean := s.Histograms[0].H.Copy()
 			for i, h := range s.Histograms[1:] {
 				count := float64(i + 2)
 				left := h.H.Copy().Div(count)
 				right := mean.Copy().Div(count)
-				toAdd, err := left.Sub(right)
+				toAdd, counterResetCollision, err := left.Sub(right)
 				if err != nil {
 					return mean, err
 				}
-				_, err = mean.Add(toAdd)
+				if counterResetCollision {
+					annos.Add(annotations.NewHistogramCounterResetCollisionWarning(args[0].PositionRange()))
+				}
+				_, counterResetCollision, err = mean.Add(toAdd)
 				if err != nil {
 					return mean, err
 				}
+				if counterResetCollision {
+					annos.Add(annotations.NewHistogramCounterResetCollisionWarning(args[0].PositionRange()))
+				}
 			}
 			return mean, nil
 		})
@@ -724,7 +741,7 @@ func funcAvgOverTime(_ []Vector, matrixVal Matrix, args parser.Expressions, enh
 				return enh.Out, annotations.New().Add(annotations.NewIncompatibleCustomBucketsHistogramsWarning(metricName, args[0].PositionRange()))
 			}
 		}
-		return vec, nil
+		return vec, annos
 	}
 	return aggrOverTime(matrixVal, enh, func(s Series) float64 {
 		var (
@@ -901,13 +918,17 @@ func funcSumOverTime(_ []Vector, matrixVal Matrix, args parser.Expressions, enh
 	}
 	if len(firstSeries.Floats) == 0 {
 		// The passed values only contain histograms.
+		var annos annotations.Annotations
 		vec, err := aggrHistOverTime(matrixVal, enh, func(s Series) (*histogram.FloatHistogram, error) {
 			sum := s.Histograms[0].H.Copy()
 			for _, h := range s.Histograms[1:] {
-				_, err := sum.Add(h.H)
+				_, counterResetCollision, err := sum.Add(h.H)
 				if err != nil {
 					return sum, err
 				}
+				if counterResetCollision {
+					annos.Add(annotations.NewHistogramCounterResetCollisionWarning(args[0].PositionRange()))
+				}
 			}
 			return sum, nil
 		})
@@ -919,7 +940,7 @@ func funcSumOverTime(_ []Vector, matrixVal Matrix, args parser.Expressions, enh
 				return enh.Out, annotations.New().Add(annotations.NewIncompatibleCustomBucketsHistogramsWarning(metricName, args[0].PositionRange()))
 			}
 		}
-		return vec, nil
+		return vec, annos
 	}
 	return aggrOverTime(matrixVal, enh, func(s Series) float64 {
 		var sum, c float64

promql/functions_internal_test.go

@@ -19,6 +19,10 @@ import (
 	"testing"
 
 	"github.com/stretchr/testify/require"
+
+	"github.com/prometheus/prometheus/model/histogram"
+	"github.com/prometheus/prometheus/promql/parser/posrange"
+	"github.com/prometheus/prometheus/util/annotations"
 )
 
 func TestKahanSumInc(t *testing.T) {
@@ -79,3 +83,51 @@ func TestKahanSumInc(t *testing.T) {
 		})
 	}
 }
+
+func newAnnotations(errs ...error) annotations.Annotations {
+	var annos annotations.Annotations
+	for _, err := range errs {
+		annos.Add(err)
+	}
+	return annos
+}
+
+// TODO(juliusmh): this test ensures histogramRate sets correct annotations.
+// This test can be removed in favor of a user facing promqltest when
+// https://github.com/prometheus/prometheus/issues/15346 is resolved.
+func TestHistogramRate_Annotations(t *testing.T) {
+	const metricName = "test"
+	pos := posrange.PositionRange{}
+	for _, tc := range []struct {
+		name            string
+		points          []HPoint
+		wantAnnotations annotations.Annotations
+	}{
+		{
+			name: "empty histograms",
+			points: []HPoint{
+				{H: &histogram.FloatHistogram{}},
+				{H: &histogram.FloatHistogram{}},
+			},
+			wantAnnotations: newAnnotations(
+				annotations.NewNativeHistogramNotGaugeWarning(metricName, pos),
+			),
+		},
+		{
+			name: "counter reset hint collision",
+			points: []HPoint{
+				{H: &histogram.FloatHistogram{CounterResetHint: histogram.NotCounterReset}},
+				{H: &histogram.FloatHistogram{CounterResetHint: histogram.CounterReset}},
+			},
+			wantAnnotations: newAnnotations(
+				annotations.NewNativeHistogramNotGaugeWarning(metricName, pos),
+				annotations.NewHistogramCounterResetCollisionWarning(pos),
+			),
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			_, annos := histogramRate(tc.points, false, metricName, pos)
+			require.Equal(t, tc.wantAnnotations, annos)
+		})
+	}
+}

promql/parser/parse.go

@@ -494,13 +494,15 @@ func (p *parser) mergeMaps(left, right *map[string]interface{}) (ret *map[string
 
 func (p *parser) histogramsIncreaseSeries(base, inc *histogram.FloatHistogram, times uint64) ([]SequenceValue, error) {
 	return p.histogramsSeries(base, inc, times, func(a, b *histogram.FloatHistogram) (*histogram.FloatHistogram, error) {
-		return a.Add(b)
+		res, _, err := a.Add(b)
+		return res, err
 	})
 }
 
 func (p *parser) histogramsDecreaseSeries(base, inc *histogram.FloatHistogram, times uint64) ([]SequenceValue, error) {
 	return p.histogramsSeries(base, inc, times, func(a, b *histogram.FloatHistogram) (*histogram.FloatHistogram, error) {
-		return a.Sub(b)
+		res, _, err := a.Sub(b)
+		return res, err
 	})
 }
 

rules/manager_test.go

@@ -1505,7 +1505,7 @@ func TestNativeHistogramsInRecordingRules(t *testing.T) {
 
 	expHist := hists[0].ToFloat(nil)
 	for _, h := range hists[1:] {
-		expHist, err = expHist.Add(h.ToFloat(nil))
+		expHist, _, err = expHist.Add(h.ToFloat(nil))
 		require.NoError(t, err)
 	}
 

util/annotations/annotations.go

@@ -155,6 +155,7 @@ var (
 	NativeHistogramQuantileNaNResultInfo    = fmt.Errorf("%w: input to histogram_quantile has NaN observations, result is NaN", PromQLInfo)
 	NativeHistogramQuantileNaNSkewInfo      = fmt.Errorf("%w: input to histogram_quantile has NaN observations, result is skewed higher", PromQLInfo)
 	NativeHistogramFractionNaNsInfo         = fmt.Errorf("%w: input to histogram_fraction has NaN observations, which are excluded from all fractions", PromQLInfo)
+	HistogramCounterResetCollisionWarning   = fmt.Errorf("%w: conflicting histogram counter resets", PromQLWarning)
 )
 
 type annoErr struct {
@@ -356,3 +357,12 @@ func NewNativeHistogramFractionNaNsInfo(metricName string, pos posrange.Position
 		Err:           maybeAddMetricName(NativeHistogramFractionNaNsInfo, metricName),
 	}
 }
+
+// NewHistogramCounterResetCollisionWarning is used when two counter histograms are added or subtracted where one has
+// a CounterReset hint and the other has NotCounterReset.
+func NewHistogramCounterResetCollisionWarning(pos posrange.PositionRange) error {
+	return annoErr{
+		PositionRange: pos,
+		Err:           fmt.Errorf("%w", HistogramCounterResetCollisionWarning),
+	}
+}