/
buffer.go
163 lines (142 loc) · 3.85 KB
/
buffer.go
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// Copyright 2019 Keybase, Inc. All rights reserved. Use of
// this source code is governed by the included BSD license.
package logger
import (
"bufio"
"io"
"sync"
"time"
"github.com/keybase/go-logging"
)
const loggingFrequency = 10 * time.Millisecond
type BufferedLoggerConfig struct {
Frequency time.Duration
Size int
}
type triggerableTimer struct {
C chan struct{}
timer *time.Timer
sentinelCh chan struct{}
shutdownCh chan struct{}
}
func newTriggerableTimer(d time.Duration) *triggerableTimer {
t := &triggerableTimer{
C: make(chan struct{}, 1),
sentinelCh: make(chan struct{}, 1),
timer: time.NewTimer(0),
shutdownCh: make(chan struct{}),
}
go func() {
for {
select {
case <-t.timer.C:
<-t.sentinelCh
t.C <- struct{}{}
case <-t.shutdownCh:
t.timer.Stop()
return
}
}
}()
return t
}
func (t *triggerableTimer) ResetIfStopped(d time.Duration) {
if d == 0 {
return
}
select {
case t.sentinelCh <- struct{}{}:
t.timer.Reset(d)
default:
}
}
func (t *triggerableTimer) Close() {
close(t.shutdownCh)
}
type autoFlushingBufferedWriter struct {
lock sync.RWMutex
bufferedWriter *bufio.Writer
backupWriter *bufio.Writer
frequency time.Duration
timer *triggerableTimer
shutdown chan struct{}
doneShutdown chan struct{}
}
var _ io.Writer = &autoFlushingBufferedWriter{}
func (writer *autoFlushingBufferedWriter) backgroundFlush() {
for {
select {
case <-writer.timer.C:
// Swap out active and backup writers
writer.lock.Lock()
writer.bufferedWriter, writer.backupWriter = writer.
backupWriter, writer.bufferedWriter
writer.lock.Unlock()
writer.backupWriter.Flush()
case <-writer.shutdown:
writer.timer.shutdownCh <- struct{}{}
writer.bufferedWriter.Flush()
// If anyone is listening, notify them that we are done shutting down.
select {
case writer.doneShutdown <- struct{}{}:
default:
}
return
}
}
}
func defaultBufferedLoggerConfig() *BufferedLoggerConfig {
return &BufferedLoggerConfig{
Frequency: loggingFrequency,
Size: 4096,
}
}
// NewAutoFlushingBufferedWriter returns an io.Writer that buffers its output
// and flushes automatically after `flushFrequency`.
func NewAutoFlushingBufferedWriter(baseWriter io.Writer,
config *BufferedLoggerConfig) (w io.Writer, shutdown chan struct{}, done chan struct{}) {
if config == nil {
config = defaultBufferedLoggerConfig()
}
result := &autoFlushingBufferedWriter{
bufferedWriter: bufio.NewWriterSize(baseWriter, config.Size),
backupWriter: bufio.NewWriterSize(baseWriter, config.Size),
frequency: config.Frequency,
timer: newTriggerableTimer(config.Frequency),
shutdown: make(chan struct{}),
doneShutdown: make(chan struct{}),
}
go result.backgroundFlush()
return result, result.shutdown, result.doneShutdown
}
func (writer *autoFlushingBufferedWriter) Write(p []byte) (int, error) {
// The locked resource here, the pointer bufferedWriter, is only being read
// even though this function is Write.
writer.lock.RLock()
defer writer.lock.RUnlock()
n, err := writer.bufferedWriter.Write(p)
if err != nil {
return n, err
}
writer.timer.ResetIfStopped(writer.frequency)
return n, nil
}
// EnableBufferedLogging turns on buffered logging - this is a performance
// boost at the expense of not getting all the logs in a crash.
func EnableBufferedLogging() {
writer, shutdown, done := NewAutoFlushingBufferedWriter(ErrorWriter(), nil)
stdErrLoggingShutdown = shutdown
stdErrLoggingShutdownDone = done
logBackend := logging.NewLogBackend(writer, "", 0)
logging.SetBackend(logBackend)
}
// Shutdown shuts down logger, flushing remaining logs if a backend with
// buffering is used.
func Shutdown() {
select {
case stdErrLoggingShutdown <- struct{}{}:
// Wait till logger is done
<-stdErrLoggingShutdownDone
default:
}
}