histogram sum is not correct example

main.go

package main

import (
	"fmt"
	"net/http"
	"time"

	"github.com/prometheus/client_golang/prometheus"
	tally "github.com/uber-go/tally/v4"
	promreporter "github.com/uber-go/tally/v4/prometheus"
)

func main() {
	reg := prometheus.NewRegistry()
	r := promreporter.NewReporter(promreporter.Options{
		Registerer: reg,
	})

	// Note: `promreporter.DefaultSeparator` is "_".
	// Prometheus doesnt like metrics with "." or "-" in them.
	scope, closer := tally.NewRootScope(tally.ScopeOptions{
		Tags:           map[string]string{},
		CachedReporter: r,
		Separator:      promreporter.DefaultSeparator,
	}, 1*time.Second)
	defer closer.Close()

	boundaries := []float64{
		1,
		11,
		111,
	}
	histogram := scope.Tagged(map[string]string{
		"foo": "quk",
	}).Histogram("test_histogram", tally.ValueBuckets(boundaries))

	go func() {
		for {
			time.Sleep(time.Second)
			histogram.RecordValue(10)
		}
	}()

	http.Handle("/metrics", r.HTTPHandler())
	fmt.Printf("Serving :8080/metrics\n")
	fmt.Printf("%v\n", http.ListenAndServe(":8080", nil))
	select {}
}

sample_output.txt

# HELP test_histogram test_histogram histogram
# TYPE test_histogram histogram
test_histogram_bucket{foo="quk",le="1"} 0
test_histogram_bucket{foo="quk",le="11"} 21
test_histogram_bucket{foo="quk",le="111"} 21
test_histogram_bucket{foo="quk",le="+Inf"} 21
test_histogram_sum{foo="quk"} 231
test_histogram_count{foo="quk"} 21

test_histogram_sum should always be a multiple of 10, but instead it is a multiple of 11