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109 lines
3.4 KiB
Go
109 lines
3.4 KiB
Go
// Copyright 2025 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package histogram
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import (
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"errors"
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"fmt"
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"math"
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"github.com/prometheus/prometheus/model/labels"
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)
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// ConvertNHCBToClassic converts Native Histogram Custom Buckets (NHCB) to classic histogram series.
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// This conversion is needed in various scenarios where users need to get NHCB back to classic histogram format,
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// such as Remote Write v1 for external system compatibility and migration use cases.
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func ConvertNHCBToClassic(nhcb any, lset labels.Labels, lsetBuilder *labels.Builder, emitSeriesFn func(labels labels.Labels, value float64) error) error {
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baseName := lset.Get("__name__")
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if baseName == "" {
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return errors.New("metric name label '__name__' is missing")
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}
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oldLabels := lsetBuilder.Labels()
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defer lsetBuilder.Reset(oldLabels)
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var (
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customValues []float64
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positiveBuckets []float64
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count, sum float64
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)
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switch h := nhcb.(type) {
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case *Histogram:
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if !IsCustomBucketsSchema(h.Schema) {
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return errors.New("unsupported histogram schema, not a NHCB")
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}
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customValues = h.CustomValues
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positiveBuckets = make([]float64, len(h.PositiveBuckets))
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for i, v := range h.PositiveBuckets {
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if i == 0 {
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positiveBuckets[i] = float64(v)
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} else {
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positiveBuckets[i] = float64(v) + positiveBuckets[i-1]
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}
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}
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count = float64(h.Count)
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sum = h.Sum
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case *FloatHistogram:
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if !IsCustomBucketsSchema(h.Schema) {
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return errors.New("unsupported histogram schema, not a NHCB")
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}
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customValues = h.CustomValues
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positiveBuckets = h.PositiveBuckets
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count = h.Count
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sum = h.Sum
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default:
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return fmt.Errorf("unsupported histogram type: %T", h)
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}
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// Each customValue corresponds to a positive bucket (aligned with the "le" label).
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// The lengths of customValues and positiveBuckets must match to avoid inconsistencies
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// while mapping bucket counts to their upper bounds.
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if len(customValues) != len(positiveBuckets) {
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return errors.New("mismatched lengths of custom values and positive buckets")
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}
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currCount := float64(0)
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for i := range customValues {
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currCount = positiveBuckets[i]
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lsetBuilder.Reset(lset)
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lsetBuilder.Set("__name__", baseName+"_bucket")
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lsetBuilder.Set("le", labels.FormatOpenMetricsFloat(customValues[i]))
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if err := emitSeriesFn(lsetBuilder.Labels(), currCount); err != nil {
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return err
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}
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}
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lsetBuilder.Reset(lset)
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lsetBuilder.Set("__name__", baseName+"_bucket")
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lsetBuilder.Set("le", labels.FormatOpenMetricsFloat(math.Inf(1)))
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if err := emitSeriesFn(lsetBuilder.Labels(), currCount); err != nil {
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return err
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}
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lsetBuilder.Reset(lset)
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lsetBuilder.Set("__name__", baseName+"_count")
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if err := emitSeriesFn(lsetBuilder.Labels(), count); err != nil {
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return err
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}
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lsetBuilder.Reset(lset)
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lsetBuilder.Set("__name__", baseName+"_sum")
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if err := emitSeriesFn(lsetBuilder.Labels(), sum); err != nil {
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return err
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}
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return nil
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}
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