func watchFile(name string) (filenotify.FileWatcher, error) {
fileWatcher, err := filenotify.New()
if err != nil {
return nil, err
}
if err := fileWatcher.Add(name); err != nil {
logrus.WithField("logger", "json-file").Warnf("falling back to file poller due to error: %v", err)
fileWatcher.Close()
fileWatcher = filenotify.NewPollingWatcher()
if err := fileWatcher.Add(name); err != nil {
fileWatcher.Close()
logrus.Debugf("error watching log file for modifications: %v", err)
return nil, err
}
}
return fileWatcher, nil
}
func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate chan interface{}, since time.Time) {
dec := json.NewDecoder(f)
l := &jsonlog.JSONLog{}
fileWatcher, err := filenotify.New()
if err != nil {
logWatcher.Err <- err
}
defer func() {
f.Close()
fileWatcher.Close()
}()
name := f.Name()
if err := fileWatcher.Add(name); err != nil {
logrus.WithField("logger", "json-file").Warnf("falling back to file poller due to error: %v", err)
fileWatcher.Close()
fileWatcher = filenotify.NewPollingWatcher()
if err := fileWatcher.Add(name); err != nil {
logrus.Debugf("error watching log file for modifications: %v", err)
logWatcher.Err <- err
return
}
}
var retries int
for {
msg, err := decodeLogLine(dec, l)
if err != nil {
if err != io.EOF {
// try again because this shouldn't happen
if _, ok := err.(*json.SyntaxError); ok && retries <= maxJSONDecodeRetry {
dec = json.NewDecoder(f)
retries++
continue
}
// io.ErrUnexpectedEOF is returned from json.Decoder when there is
// remaining data in the parser's buffer while an io.EOF occurs.
// If the json logger writes a partial json log entry to the disk
// while at the same time the decoder tries to decode it, the race condition happens.
if err == io.ErrUnexpectedEOF && retries <= maxJSONDecodeRetry {
reader := io.MultiReader(dec.Buffered(), f)
dec = json.NewDecoder(reader)
retries++
continue
}
return
}
select {
case <-fileWatcher.Events():
dec = json.NewDecoder(f)
continue
case <-fileWatcher.Errors():
logWatcher.Err <- err
return
case <-logWatcher.WatchClose():
fileWatcher.Remove(name)
return
case <-notifyRotate:
f.Close()
fileWatcher.Remove(name)
// retry when the file doesn't exist
for retries := 0; retries <= 5; retries++ {
f, err = os.Open(name)
if err == nil || !os.IsNotExist(err) {
break
}
}
if err = fileWatcher.Add(name); err != nil {
logWatcher.Err <- err
return
}
if err != nil {
logWatcher.Err <- err
return
}
dec = json.NewDecoder(f)
continue
}
}
retries = 0 // reset retries since we've succeeded
if !since.IsZero() && msg.Timestamp.Before(since) {
continue
}
select {
case logWatcher.Msg <- msg:
case <-logWatcher.WatchClose():
logWatcher.Msg <- msg
for {
msg, err := decodeLogLine(dec, l)
if err != nil {
return
}
if !since.IsZero() && msg.Timestamp.Before(since) {
continue
}
logWatcher.Msg <- msg
}
}
}
}