src/runtime/metrics/histogram.go

// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package metrics

// Float64Histogram represents a distribution of float64 values.
type Float64Histogram struct {
	// Counts contains the weights for each histogram bucket.
	//
	// Given N buckets, Count[n] is the weight of the range
	// [bucket[n], bucket[n+1]), for 0 <= n < N.
	Counts []uint64

	// Buckets contains the boundaries of the histogram buckets, in increasing order.
	//
	// Buckets[0] is the inclusive lower bound of the minimum bucket while
	// Buckets[len(Buckets)-1] is the exclusive upper bound of the maximum bucket.
	// Hence, there are len(Buckets)-1 counts. Furthermore, len(Buckets) != 1, always,
	// since at least two boundaries are required to describe one bucket (and 0
	// boundaries are used to describe 0 buckets).
	//
	// Buckets[0] is permitted to have value -Inf and Buckets[len(Buckets)-1] is
	// permitted to have value Inf.
	//
	// For a given metric name, the value of Buckets is guaranteed not to change
	// between calls until program exit.
	//
	// This slice value is permitted to alias with other Float64Histograms' Buckets
	// fields, so the values within should only ever be read. If they need to be
	// modified, the user must make a copy.
	Buckets []float64
}