Implementing Native Histograms

native_histograms:
  max_buckets: 128
  min_age: 1h

prometheus --enable-feature=native-histograms

scrape_configs:
  - job_name: "prometheus"
    scrape_interval: 15s
    metrics_path: /metrics
    native_histograms: true
    static_configs:
      - targets: [localhost:9090]

histogram_quantile(0.95, http_request_duration_seconds)

histogram_quantile(0.9, native_histogram_metric) / histogram_quantile(0.9, regular_histogram_metric)

histogram_quantile(0.95, http_request_duration_seconds)

histogram_quantile(0.99, http_request_duration_seconds_bucket)

prometheus:
  enable_native_histograms: true
  histogram_config:
    schema: 1

groups:
- name: example
  rules:
  - record: http_requests_native
    expr: histogram_quantile(0.95, sum by (le) (rate(http_requests_total[5m])))

const histogram = {
  buckets: [10, 20, 30, 40, 50],
  counts: [5, 10, 15, 8, 2]
};

const sum = histogram.buckets.reduce((acc, bucket, i) => acc + (bucket * histogram.counts[i]), 0);
const count = histogram.counts.reduce((acc, c) => acc + c, 0);

console.log("Sum:", sum); // Sum: 10*5 + 20*10 + 30*15 + 40*8 + 50*2 = 50 + 200 + 450 + 320 + 100 = 1120
console.log("Count:", count); // Count: 40

function calculateQuantile(histogram, q) {
  const total = histogram.counts.reduce((a, b) => a + b, 0);
  const target = q * total;
  let cumulative = 0;
  for (let i = 0; i < histogram.buckets.length; i++) {
    cumulative += histogram.counts[i];
    if (cumulative >= target) {
      return histogram.buckets[i];
    }
  }
  return histogram.buckets[histogram.buckets.length - 1];
}

const q90 = calculateQuantile(histogram, 0.9);
console.log("90th Percentile:", q90); // 40

import "github.com/prometheus/client_model/go"

func MergeHistograms(hists []*client_model.Histogram) *client_model.Histogram {
    if len(hists) == 0 {
        return nil
    }

    // Initialize result with first histogram's schema and buckets
    result := &client_model.Histogram{
        Schema:     hists[0].Schema,
        ZeroThreshold: hists[0].ZeroThreshold,
        ZeroCount:  hists[0].ZeroCount,
        Count:      hists[0].Count,
        Sum:        hists[0].Sum,
    }

    // Merge buckets and aggregate counts
    for i := 1; i < len(hists); i++ {
        // Merge bucket counts and update sum
        result.Count += hists[i].Count
        result.Sum += hists[i].Sum
    }

    return result
}

prometheus:
  storage:
    native_histograms:
      bucket_limit: 512
      max_age: 48h
      min_bucket: 1e-08

native_histogram_bucket_limit: 200
native_histogram_max_bucket: 1000000

groups:
- name: example
  rules:
  - alert: HighLatency
    expr: histogram_quantile(0.95, rate(request_duration_seconds_bucket[5m])) > 1
    for: 10m
    labels:
      severity: page
    annotations:
      summary: "High latency detected"
      description: "The 95th percentile request duration is above 1 second."