prometheus/pkg/logging/dedupe.go

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// Copyright 2019 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package logging
import (
"bytes"
"sync"
"time"
"github.com/go-kit/kit/log"
"github.com/go-logfmt/logfmt"
)
const (
garbageCollectEvery = 10 * time.Second
expireEntriesAfter = 1 * time.Minute
maxEntries = 1024
)
type logfmtEncoder struct {
*logfmt.Encoder
buf bytes.Buffer
}
var logfmtEncoderPool = sync.Pool{
New: func() interface{} {
var enc logfmtEncoder
enc.Encoder = logfmt.NewEncoder(&enc.buf)
return &enc
},
}
// Deduper implement log.Logger, dedupes log lines.
type Deduper struct {
next log.Logger
repeat time.Duration
quit chan struct{}
mtx sync.RWMutex
seen map[string]time.Time
}
// Dedupe log lines to next, only repeating every repeat duration.
func Dedupe(next log.Logger, repeat time.Duration) *Deduper {
d := &Deduper{
next: next,
repeat: repeat,
quit: make(chan struct{}),
seen: map[string]time.Time{},
}
go d.run()
return d
}
// Stop the Deduper.
func (d *Deduper) Stop() {
close(d.quit)
}
func (d *Deduper) run() {
ticker := time.NewTicker(garbageCollectEvery)
defer ticker.Stop()
for {
select {
case <-ticker.C:
d.mtx.Lock()
now := time.Now()
for line, seen := range d.seen {
if now.Sub(seen) > expireEntriesAfter {
delete(d.seen, line)
}
}
d.mtx.Unlock()
case <-d.quit:
return
}
}
}
// Log implements log.Logger.
func (d *Deduper) Log(keyvals ...interface{}) error {
line, err := encode(keyvals...)
if err != nil {
return err
}
d.mtx.RLock()
last, ok := d.seen[line]
d.mtx.RUnlock()
if ok && time.Since(last) < d.repeat {
return nil
}
d.mtx.Lock()
if len(d.seen) < maxEntries {
d.seen[line] = time.Now()
}
d.mtx.Unlock()
return d.next.Log(keyvals...)
}
func encode(keyvals ...interface{}) (string, error) {
enc := logfmtEncoderPool.Get().(*logfmtEncoder)
enc.buf.Reset()
defer logfmtEncoderPool.Put(enc)
if err := enc.EncodeKeyvals(keyvals...); err != nil {
return "", err
}
// Add newline to the end of the buffer
if err := enc.EndRecord(); err != nil {
return "", err
}
return enc.buf.String(), nil
}