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Buffer all the output in memory before writing it to the provided io.Writer in WritePrometheus

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This should prevent from indefinite locking of internal structures in the case of laggy io.Writer
This commit is contained in:
Aliaksandr Valialkin 2019-11-25 13:01:23 +02:00
parent 839018719c
commit eb780f4caa
1 changed files with 5 additions and 1 deletions
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6
set.go
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@ -1,6 +1,7 @@
package metrics package metrics
import ( import (
"bytes"
"fmt" "fmt"
"io" "io"
"sort" "sort"
@ -29,6 +30,8 @@ func NewSet() *Set {
// WritePrometheus writes all the metrics from s to w in Prometheus format. // WritePrometheus writes all the metrics from s to w in Prometheus format.
func (s *Set) WritePrometheus(w io.Writer) { func (s *Set) WritePrometheus(w io.Writer) {
// Collect all the metrics in in-memory buffer in order to prevent from long locking due to slow w.
var bb bytes.Buffer
lessFunc := func(i, j int) bool { lessFunc := func(i, j int) bool {
return s.a[i].name < s.a[j].name return s.a[i].name < s.a[j].name
} }
@ -40,9 +43,10 @@ func (s *Set) WritePrometheus(w io.Writer) {
sort.Slice(s.a, lessFunc) sort.Slice(s.a, lessFunc)
} }
for _, nm := range s.a { for _, nm := range s.a {
nm.metric.marshalTo(nm.name, w) nm.metric.marshalTo(nm.name, &bb)
} }
s.mu.Unlock() s.mu.Unlock()
w.Write(bb.Bytes())
} }
// NewHistogram creates and returns new histogram in s with the given name. // NewHistogram creates and returns new histogram in s with the given name.