Merge pull request #24514 from cpuguy83/fix_log_follow_rotate
Fix issues with tailing rotated jsonlog file
This commit is contained in:
Aaron Lehmann
GitHub
commit
cbd4e4d48a
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@ -3,11 +3,14 @@ package jsonfilelog
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import (
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"bytes"
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"encoding/json"
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"errors"
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"fmt"
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"io"
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"os"
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"time"
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"gopkg.in/fsnotify.v1"
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"github.com/Sirupsen/logrus"
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"github.com/docker/docker/daemon/logger"
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"github.com/docker/docker/pkg/filenotify"
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@ -44,6 +47,10 @@ func (l *JSONFileLogger) ReadLogs(config logger.ReadConfig) *logger.LogWatcher {
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func (l *JSONFileLogger) readLogs(logWatcher *logger.LogWatcher, config logger.ReadConfig) {
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defer close(logWatcher.Msg)
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// lock so the read stream doesn't get corrupted due to rotations or other log data written while we read
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// This will block writes!!!
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l.mu.Lock()
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pth := l.writer.LogPath()
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var files []io.ReadSeeker
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for i := l.writer.MaxFiles(); i > 1; i-- {
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@ -63,6 +70,7 @@ func (l *JSONFileLogger) readLogs(logWatcher *logger.LogWatcher, config logger.R
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latestFile, err := os.Open(pth)
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if err != nil {
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logWatcher.Err <- err
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l.mu.Unlock()
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return
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}
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defer latestFile.Close()
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@ -83,6 +91,7 @@ func (l *JSONFileLogger) readLogs(logWatcher *logger.LogWatcher, config logger.R
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if err := latestFile.Close(); err != nil {
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logrus.Errorf("Error closing file: %v", err)
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}
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l.mu.Unlock()
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return
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}
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@ -90,7 +99,6 @@ func (l *JSONFileLogger) readLogs(logWatcher *logger.LogWatcher, config logger.R
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latestFile.Seek(0, os.SEEK_END)
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}
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l.mu.Lock()
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l.readers[logWatcher] = struct{}{}
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l.mu.Unlock()
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@ -131,19 +139,11 @@ func tailFile(f io.ReadSeeker, logWatcher *logger.LogWatcher, tail int, since ti
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}
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}
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func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan interface{}, since time.Time) {
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dec := json.NewDecoder(f)
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l := &jsonlog.JSONLog{}
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func watchFile(name string) (filenotify.FileWatcher, error) {
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fileWatcher, err := filenotify.New()
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if err != nil {
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logWatcher.Err <- err
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return nil, err
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}
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defer func() {
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f.Close()
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fileWatcher.Close()
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}()
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name := f.Name()
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if err := fileWatcher.Add(name); err != nil {
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logrus.WithField("logger", "json-file").Warnf("falling back to file poller due to error: %v", err)
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@ -151,72 +151,136 @@ func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan int
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fileWatcher = filenotify.NewPollingWatcher()
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if err := fileWatcher.Add(name); err != nil {
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fileWatcher.Close()
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logrus.Debugf("error watching log file for modifications: %v", err)
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logWatcher.Err <- err
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return
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return nil, err
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}
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}
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return fileWatcher, nil
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}
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func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan interface{}, since time.Time) {
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dec := json.NewDecoder(f)
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l := &jsonlog.JSONLog{}
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name := f.Name()
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fileWatcher, err := watchFile(name)
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if err != nil {
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logWatcher.Err <- err
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return
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}
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defer func() {
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f.Close()
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fileWatcher.Close()
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}()
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var retries int
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handleRotate := func() error {
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f.Close()
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fileWatcher.Remove(name)
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// retry when the file doesn't exist
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for retries := 0; retries <= 5; retries++ {
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f, err = os.Open(name)
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if err == nil || !os.IsNotExist(err) {
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break
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}
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}
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if err != nil {
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return err
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}
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if err := fileWatcher.Add(name); err != nil {
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return err
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}
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dec = json.NewDecoder(f)
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return nil
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}
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errRetry := errors.New("retry")
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errDone := errors.New("done")
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waitRead := func() error {
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select {
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case e := <-fileWatcher.Events():
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switch e.Op {
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case fsnotify.Write:
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dec = json.NewDecoder(f)
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return nil
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case fsnotify.Rename, fsnotify.Remove:
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select {
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case <-notifyRotate:
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case <-logWatcher.WatchClose():
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fileWatcher.Remove(name)
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return errDone
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}
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if err := handleRotate(); err != nil {
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return err
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}
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return nil
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}
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return errRetry
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case err := <-fileWatcher.Errors():
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logrus.Debug("logger got error watching file: %v", err)
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// Something happened, let's try and stay alive and create a new watcher
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if retries <= 5 {
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fileWatcher.Close()
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fileWatcher, err = watchFile(name)
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if err != nil {
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return err
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}
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retries++
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return errRetry
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}
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return err
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case <-logWatcher.WatchClose():
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fileWatcher.Remove(name)
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return errDone
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}
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}
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var retries int
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handleDecodeErr := func(err error) error {
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if err == io.EOF {
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for err := waitRead(); err != nil; {
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if err == errRetry {
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// retry the waitRead
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continue
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}
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return err
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}
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return nil
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}
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// try again because this shouldn't happen
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if _, ok := err.(*json.SyntaxError); ok && retries <= maxJSONDecodeRetry {
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dec = json.NewDecoder(f)
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retries++
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return nil
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}
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// io.ErrUnexpectedEOF is returned from json.Decoder when there is
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// remaining data in the parser's buffer while an io.EOF occurs.
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// If the json logger writes a partial json log entry to the disk
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// while at the same time the decoder tries to decode it, the race condition happens.
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if err == io.ErrUnexpectedEOF && retries <= maxJSONDecodeRetry {
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reader := io.MultiReader(dec.Buffered(), f)
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dec = json.NewDecoder(reader)
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retries++
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return nil
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}
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return err
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}
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// main loop
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for {
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msg, err := decodeLogLine(dec, l)
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if err != nil {
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if err != io.EOF {
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// try again because this shouldn't happen
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if _, ok := err.(*json.SyntaxError); ok && retries <= maxJSONDecodeRetry {
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dec = json.NewDecoder(f)
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retries++
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continue
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if err := handleDecodeErr(err); err != nil {
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if err == errDone {
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return
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}
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// io.ErrUnexpectedEOF is returned from json.Decoder when there is
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// remaining data in the parser's buffer while an io.EOF occurs.
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// If the json logger writes a partial json log entry to the disk
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// while at the same time the decoder tries to decode it, the race condition happens.
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if err == io.ErrUnexpectedEOF && retries <= maxJSONDecodeRetry {
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reader := io.MultiReader(dec.Buffered(), f)
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dec = json.NewDecoder(reader)
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retries++
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continue
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}
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return
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}
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select {
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case <-fileWatcher.Events():
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dec = json.NewDecoder(f)
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continue
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case <-fileWatcher.Errors():
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// we got an unrecoverable error, so return
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logWatcher.Err <- err
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return
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case <-logWatcher.WatchClose():
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fileWatcher.Remove(name)
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return
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case <-notifyRotate:
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f.Close()
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fileWatcher.Remove(name)
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// retry when the file doesn't exist
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for retries := 0; retries <= 5; retries++ {
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f, err = os.Open(name)
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if err == nil || !os.IsNotExist(err) {
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break
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}
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}
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if err = fileWatcher.Add(name); err != nil {
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logWatcher.Err <- err
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return
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}
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if err != nil {
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logWatcher.Err <- err
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return
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}
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dec = json.NewDecoder(f)
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continue
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}
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// ready to try again
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continue
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}
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retries = 0 // reset retries since we've succeeded
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