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daemon/logger: refactor followLogs to write more unit tests
followLogs() is getting really long (170+ lines) and complex. The function has multiple inner functions that mutate its variables. To refactor the function, this change introduces follow{} struct. The inner functions are now defined as ordinal methods, which are accessible from tests. Signed-off-by: Kazuyoshi Kato <katokazu@amazon.com>
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Original file line number | Diff line number | Diff line change |
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package loggerutils // import "github.com/docker/docker/daemon/logger/loggerutils" | ||
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import ( | ||
"io" | ||
"os" | ||
"time" | ||
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"github.com/docker/docker/daemon/logger" | ||
"github.com/docker/docker/pkg/filenotify" | ||
"github.com/fsnotify/fsnotify" | ||
"github.com/pkg/errors" | ||
"github.com/sirupsen/logrus" | ||
) | ||
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var errRetry = errors.New("retry") | ||
var errDone = errors.New("done") | ||
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type follow struct { | ||
file *os.File | ||
dec Decoder | ||
fileWatcher filenotify.FileWatcher | ||
logWatcher *logger.LogWatcher | ||
notifyRotate, notifyEvict chan interface{} | ||
oldSize int64 | ||
retries int | ||
} | ||
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func (fl *follow) handleRotate() error { | ||
name := fl.file.Name() | ||
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fl.file.Close() | ||
fl.fileWatcher.Remove(name) | ||
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// retry when the file doesn't exist | ||
var err error | ||
for retries := 0; retries <= 5; retries++ { | ||
f, err := open(name) | ||
if err == nil || !os.IsNotExist(err) { | ||
fl.file = f | ||
break | ||
} | ||
} | ||
if err != nil { | ||
return err | ||
} | ||
if err := fl.fileWatcher.Add(name); err != nil { | ||
return err | ||
} | ||
fl.dec.Reset(fl.file) | ||
return nil | ||
} | ||
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func (fl *follow) handleMustClose(evictErr error) { | ||
fl.file.Close() | ||
fl.dec.Close() | ||
fl.logWatcher.Err <- errors.Wrap(evictErr, "log reader evicted due to errors") | ||
logrus.WithField("file", fl.file.Name()).Error("Log reader notified that it must re-open log file, some log data may not be streamed to the client.") | ||
} | ||
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func (fl *follow) waitRead() error { | ||
select { | ||
case e := <-fl.notifyEvict: | ||
if e != nil { | ||
err := e.(error) | ||
fl.handleMustClose(err) | ||
} | ||
return errDone | ||
case e := <-fl.fileWatcher.Events(): | ||
switch e.Op { | ||
case fsnotify.Write: | ||
fl.dec.Reset(fl.file) | ||
return nil | ||
case fsnotify.Rename, fsnotify.Remove: | ||
select { | ||
case <-fl.notifyRotate: | ||
case <-fl.logWatcher.WatchProducerGone(): | ||
return errDone | ||
case <-fl.logWatcher.WatchConsumerGone(): | ||
return errDone | ||
} | ||
if err := fl.handleRotate(); err != nil { | ||
return err | ||
} | ||
return nil | ||
} | ||
return errRetry | ||
case err := <-fl.fileWatcher.Errors(): | ||
logrus.Debugf("logger got error watching file: %v", err) | ||
// Something happened, let's try and stay alive and create a new watcher | ||
if fl.retries <= 5 { | ||
fl.fileWatcher.Close() | ||
fl.fileWatcher, err = watchFile(fl.file.Name()) | ||
if err != nil { | ||
return err | ||
} | ||
fl.retries++ | ||
return errRetry | ||
} | ||
return err | ||
case <-fl.logWatcher.WatchProducerGone(): | ||
return errDone | ||
case <-fl.logWatcher.WatchConsumerGone(): | ||
return errDone | ||
} | ||
} | ||
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func (fl *follow) handleDecodeErr(err error) error { | ||
if !errors.Is(err, io.EOF) { | ||
return err | ||
} | ||
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// Handle special case (#39235): max-file=1 and file was truncated | ||
st, stErr := fl.file.Stat() | ||
if stErr == nil { | ||
size := st.Size() | ||
defer func() { fl.oldSize = size }() | ||
if size < fl.oldSize { // truncated | ||
fl.file.Seek(0, 0) | ||
fl.dec.Reset(fl.file) | ||
return nil | ||
} | ||
} else { | ||
logrus.WithError(stErr).Warn("logger: stat error") | ||
} | ||
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for { | ||
err := fl.waitRead() | ||
if err == nil { | ||
break | ||
} | ||
if err == errRetry { | ||
continue | ||
} | ||
return err | ||
} | ||
return nil | ||
} | ||
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func (fl *follow) mainLoop(since, until time.Time) { | ||
for { | ||
select { | ||
case err := <-fl.notifyEvict: | ||
if err != nil { | ||
fl.handleMustClose(err.(error)) | ||
} | ||
return | ||
default: | ||
} | ||
msg, err := fl.dec.Decode() | ||
if err != nil { | ||
if err := fl.handleDecodeErr(err); err != nil { | ||
if err == errDone { | ||
return | ||
} | ||
// we got an unrecoverable error, so return | ||
fl.logWatcher.Err <- err | ||
return | ||
} | ||
// ready to try again | ||
continue | ||
} | ||
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fl.retries = 0 // reset retries since we've succeeded | ||
if !since.IsZero() && msg.Timestamp.Before(since) { | ||
continue | ||
} | ||
if !until.IsZero() && msg.Timestamp.After(until) { | ||
return | ||
} | ||
// send the message, unless the consumer is gone | ||
select { | ||
case e := <-fl.notifyEvict: | ||
if e != nil { | ||
err := e.(error) | ||
logrus.WithError(err).Debug("Reader evicted while sending log message") | ||
fl.logWatcher.Err <- err | ||
} | ||
return | ||
case fl.logWatcher.Msg <- msg: | ||
case <-fl.logWatcher.WatchConsumerGone(): | ||
return | ||
} | ||
} | ||
} | ||
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func followLogs(f *os.File, logWatcher *logger.LogWatcher, notifyRotate, notifyEvict chan interface{}, dec Decoder, since, until time.Time) { | ||
dec.Reset(f) | ||
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name := f.Name() | ||
fileWatcher, err := watchFile(name) | ||
if err != nil { | ||
logWatcher.Err <- err | ||
return | ||
} | ||
defer func() { | ||
f.Close() | ||
dec.Close() | ||
fileWatcher.Close() | ||
}() | ||
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fl := &follow{ | ||
file: f, | ||
oldSize: -1, | ||
logWatcher: logWatcher, | ||
fileWatcher: fileWatcher, | ||
notifyRotate: notifyRotate, | ||
notifyEvict: notifyEvict, | ||
dec: dec, | ||
} | ||
fl.mainLoop(since, until) | ||
} |
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