Add tests according to code review

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

scrape/scrape_test.go

@@ -1742,18 +1742,24 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 	require.NoError(t, err)
 	beforeMetricValue := metric.GetCounter().GetValue()
 
-	nativeHistogram := prometheus.NewHistogram(prometheus.HistogramOpts{
+	nativeHistogram := prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
 			Namespace:                      "testing",
 			Name:                           "example_native_histogram",
 			Help:                           "This is used for testing",
 			ConstLabels:                    map[string]string{"some": "value"},
 			NativeHistogramBucketFactor:    1.1, // 10% increase from bucket to bucket
 			NativeHistogramMaxBucketNumber: 100, // intentionally higher than the limit we'll use in the scraper
-	})
+		},
+		[]string{"size"},
+	)
 	registry := prometheus.NewRegistry()
 	registry.Register(nativeHistogram)
-	nativeHistogram.Observe(1.0)
+	nativeHistogram.WithLabelValues("S").Observe(1.0)
-	nativeHistogram.Observe(10.0) // in different bucket since > 1*1.1
+	nativeHistogram.WithLabelValues("M").Observe(1.0)
+	nativeHistogram.WithLabelValues("L").Observe(1.0)
+	nativeHistogram.WithLabelValues("M").Observe(10.0)
+	nativeHistogram.WithLabelValues("L").Observe(10.0) // in different bucket since > 1*1.1
 
 	gathered, err := registry.Gather()
 	require.NoError(t, err)
@@ -1766,9 +1772,9 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 	now := time.Now()
 	total, added, seriesAdded, err := sl.append(app, msg, "application/vnd.google.protobuf", now)
 	require.NoError(t, err)
-	require.Equal(t, 1, total)
+	require.Equal(t, 3, total)
-	require.Equal(t, 1, added)
+	require.Equal(t, 3, added)
-	require.Equal(t, 1, seriesAdded)
+	require.Equal(t, 3, seriesAdded)
 
 	err = targetScrapeNativeHistogramBucketLimit.Write(&metric)
 	require.NoError(t, err)
@@ -1776,7 +1782,7 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 	require.Equal(t, beforeMetricValue, metricValue)
 	beforeMetricValue = metricValue
 
-	nativeHistogram.Observe(100.0) // in different bucket since > 10*1.1
+	nativeHistogram.WithLabelValues("L").Observe(100.0) // in different bucket since > 10*1.1
 
 	gathered, err = registry.Gather()
 	require.NoError(t, err)
@@ -1792,8 +1798,8 @@ func TestScrapeLoop_HistogramBucketLimit(t *testing.T) {
 		t.Fatalf("Did not see expected histogram bucket limit error: %s", err)
 	}
 	require.NoError(t, app.Rollback())
-	require.Equal(t, 1, total)
+	require.Equal(t, 3, total)
-	require.Equal(t, 1, added)
+	require.Equal(t, 3, added)
 	require.Equal(t, 0, seriesAdded)
 
 	err = targetScrapeNativeHistogramBucketLimit.Write(&metric)

scrape/target_test.go

@@ -31,6 +31,7 @@ import (
 
 	"github.com/prometheus/prometheus/config"
 	"github.com/prometheus/prometheus/discovery/targetgroup"
+	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 )
 
@@ -488,3 +489,63 @@ scrape_configs:
 		})
 	}
 }
+
+func TestBucketLimitAppender(t *testing.T) {
+	example := histogram.Histogram{
+		Schema:        0,
+		Count:         21,
+		Sum:           33,
+		ZeroThreshold: 0.001,
+		ZeroCount:     3,
+		PositiveSpans: []histogram.Span{
+			{Offset: 0, Length: 3},
+		},
+		PositiveBuckets: []int64{3, 0, 0},
+		NegativeSpans: []histogram.Span{
+			{Offset: 0, Length: 3},
+		},
+		NegativeBuckets: []int64{3, 0, 0},
+	}
+
+	cases := []struct {
+		h           histogram.Histogram
+		limit       int
+		expectError bool
+	}{
+		{
+			h:           example,
+			limit:       3,
+			expectError: true,
+		},
+		{
+			h:           example,
+			limit:       10,
+			expectError: false,
+		},
+	}
+
+	resApp := &collectResultAppender{}
+
+	for _, c := range cases {
+		for _, floatHisto := range []bool{true, false} {
+			t.Run(fmt.Sprintf("floatHistogram=%t", floatHisto), func(t *testing.T) {
+				app := &bucketLimitAppender{Appender: resApp, limit: c.limit}
+				ts := int64(10 * time.Minute / time.Millisecond)
+				h := c.h
+				lbls := labels.FromStrings("__name__", "sparse_histogram_series")
+				var err error
+				if floatHisto {
+					_, err = app.AppendHistogram(0, lbls, ts, nil, h.Copy().ToFloat())
+				} else {
+					_, err = app.AppendHistogram(0, lbls, ts, h.Copy(), nil)
+				}
+				if c.expectError {
+					require.Error(t, err)
+				} else {
+					require.NoError(t, err)
+				}
+				require.NoError(t, app.Commit())
+			})
+		}
+	}
+}