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histogram: expose FindBucket in Histogram API #3

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histogram: expose FindBucket in Histogram API #3

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25 changes: 16 additions & 9 deletions prometheus/histogram.go
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Original file line number Diff line number Diff line change
Expand Up @@ -260,6 +260,13 @@ type Histogram interface {
Observe(float64)
}

type HistogramInternal interface {
Histogram

ObserveInternal(float64, int)
FindBucket(v float64) int
}

// bucketLabel is used for the label that defines the upper bound of a
// bucket of a histogram ("le" -> "less or equal").
const bucketLabel = "le"
Expand Down Expand Up @@ -520,7 +527,7 @@ type HistogramVecOpts struct {
// The returned implementation also implements ExemplarObserver. It is safe to
// perform the corresponding type assertion. Exemplars are tracked separately
// for each bucket.
func NewHistogram(opts HistogramOpts) Histogram {
func NewHistogram(opts HistogramOpts) HistogramInternal {
return newHistogram(
NewDesc(
BuildFQName(opts.Namespace, opts.Subsystem, opts.Name),
Expand All @@ -532,7 +539,7 @@ func NewHistogram(opts HistogramOpts) Histogram {
)
}

func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) Histogram {
func newHistogram(desc *Desc, opts HistogramOpts, labelValues ...string) HistogramInternal {
if len(desc.variableLabels.names) != len(labelValues) {
panic(makeInconsistentCardinalityError(desc.fqName, desc.variableLabels.names, labelValues))
}
Expand Down Expand Up @@ -764,15 +771,15 @@ func (h *histogram) Desc() *Desc {
}

func (h *histogram) Observe(v float64) {
h.observe(v, h.findBucket(v))
h.ObserveInternal(v, h.FindBucket(v))
}

// ObserveWithExemplar should not be called in a high-frequency setting
// for a native histogram with configured exemplars. For this case,
// the implementation isn't lock-free and might suffer from lock contention.
func (h *histogram) ObserveWithExemplar(v float64, e Labels) {
i := h.findBucket(v)
h.observe(v, i)
i := h.FindBucket(v)
h.ObserveInternal(v, i)
h.updateExemplar(v, i, e)
}

Expand Down Expand Up @@ -861,9 +868,9 @@ func (h *histogram) Write(out *dto.Metric) error {
return nil
}

// findBucket returns the index of the bucket for the provided value, or
// FindBucket returns the index of the bucket for the provided value, or
// len(h.upperBounds) for the +Inf bucket.
func (h *histogram) findBucket(v float64) int {
func (h *histogram) FindBucket(v float64) int {
n := len(h.upperBounds)
if n == 0 {
return 0
Expand Down Expand Up @@ -896,8 +903,8 @@ func (h *histogram) findBucket(v float64) int {
return sort.SearchFloat64s(h.upperBounds, v)
}

// observe is the implementation for Observe without the findBucket part.
func (h *histogram) observe(v float64, bucket int) {
// ObserveInternal is the implementation for Observe without the FindBucket part.
func (h *histogram) ObserveInternal(v float64, bucket int) {
// Do not add to sparse buckets for NaN observations.
doSparse := h.nativeHistogramSchema > math.MinInt32 && !math.IsNaN(v)
// We increment h.countAndHotIdx so that the counter in the lower
Expand Down
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