add HistogramExt method with custom quantiles

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

README.md

@@ -1,5 +1,5 @@
 # Micro
-![Coverage](https://img.shields.io/badge/Coverage-33.8%25-yellow)
+![Coverage](https://img.shields.io/badge/Coverage-33.6%25-yellow)
 [![License](https://img.shields.io/:license-apache-blue.svg)](https://opensource.org/licenses/Apache-2.0)
 [![Doc](https://img.shields.io/badge/go.dev-reference-007d9c?logo=go&logoColor=white&style=flat-square)](https://pkg.go.dev/go.unistack.org/micro/v4?tab=overview)
 [![Status](https://git.unistack.org/unistack-org/micro/actions/workflows/job_tests.yml/badge.svg?branch=v4)](https://git.unistack.org/unistack-org/micro/actions?query=workflow%3Abuild+branch%3Av4+event%3Apush)

meter/meter.go

@@ -49,9 +49,11 @@ type Meter interface {
 	Set(opts ...Option) Meter
 	// Histogram get or create histogram
 	Histogram(name string, labels ...string) Histogram
+	// HistogramExt get or create histogram with specified quantiles
+	HistogramExt(name string, quantiles []float64, labels ...string) Histogram
 	// Summary get or create summary
 	Summary(name string, labels ...string) Summary
-	// SummaryExt get or create summary with spcified quantiles and window time
+	// SummaryExt get or create summary with specified quantiles and window time
 	SummaryExt(name string, window time.Duration, quantiles []float64, labels ...string) Summary
 	// Write writes metrics to io.Writer
 	Write(w io.Writer, opts ...Option) error

meter/noop.go

@@ -70,6 +70,11 @@ func (r *noopMeter) Histogram(_ string, labels ...string) Histogram {
 	return &noopHistogram{labels: labels}
 }
 
+// HistogramExt implements the Meter interface
+func (r *noopMeter) HistogramExt(_ string, quantiles []float64, labels ...string) Histogram {
+	return &noopHistogram{labels: labels}
+}
+
 // Set implements the Meter interface
 func (r *noopMeter) Set(opts ...Option) Meter {
 	m := &noopMeter{opts: r.opts}

meter/options.go

@@ -4,6 +4,8 @@ import (
 	"context"
 )
 
+var DefaultQuantiles = []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10}
+
 // Option powers the configuration for metrics implementations:
 type Option func(*Options)
 
@@ -23,6 +25,8 @@ type Options struct {
 	WriteProcessMetrics bool
 	// WriteFDMetrics flag to write fd metrics
 	WriteFDMetrics bool
+	// Quantiles specifies buckets for histogram
+	Quantiles []float64
 }
 
 // NewOptions prepares a set of options:
@@ -61,14 +65,12 @@ func Address(value string) Option {
 	}
 }
 
-/*
-// TimingObjectives defines the desired spread of statistics for histogram / timing metrics:
-func TimingObjectives(value map[float64]float64) Option {
+// Quantiles defines the desired spread of statistics for histogram metrics:
+func Quantiles(quantiles []float64) Option {
 	return func(o *Options) {
-		o.TimingObjectives = value
+		o.Quantiles = quantiles
 	}
 }
-*/
 
 // Labels add the meter labels
 func Labels(ls ...string) Option {