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logfile.go
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logfile.go
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package loggerutils // import "github.com/docker/docker/daemon/logger/loggerutils"
import (
"compress/gzip"
"context"
"encoding/json"
"fmt"
"io"
"os"
"runtime"
"strconv"
"strings"
"sync"
"time"
"github.com/docker/docker/daemon/logger"
"github.com/docker/docker/pkg/filenotify"
"github.com/docker/docker/pkg/pools"
"github.com/docker/docker/pkg/pubsub"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
)
const tmpLogfileSuffix = ".tmp"
// rotateFileMetadata is a metadata of the gzip header of the compressed log file
type rotateFileMetadata struct {
LastTime time.Time `json:"lastTime,omitempty"`
}
// refCounter is a counter of logfile being referenced
type refCounter struct {
mu sync.Mutex
counter map[string]int
}
// Reference increase the reference counter for specified logfile
func (rc *refCounter) GetReference(fileName string, openRefFile func(fileName string, exists bool) (*os.File, error)) (*os.File, error) {
rc.mu.Lock()
defer rc.mu.Unlock()
var (
file *os.File
err error
)
_, ok := rc.counter[fileName]
file, err = openRefFile(fileName, ok)
if err != nil {
return nil, err
}
if ok {
rc.counter[fileName]++
} else if file != nil {
rc.counter[file.Name()] = 1
}
return file, nil
}
// Dereference reduce the reference counter for specified logfile
func (rc *refCounter) Dereference(fileName string) error {
rc.mu.Lock()
defer rc.mu.Unlock()
rc.counter[fileName]--
if rc.counter[fileName] <= 0 {
delete(rc.counter, fileName)
err := os.Remove(fileName)
if err != nil && !os.IsNotExist(err) {
return err
}
}
return nil
}
// LogFile is Logger implementation for default Docker logging.
type LogFile struct {
mu sync.RWMutex // protects the logfile access
f *os.File // store for closing
closed bool
rotateMu sync.Mutex // blocks the next rotation until the current rotation is completed
capacity int64 // maximum size of each file
currentSize int64 // current size of the latest file
maxFiles int // maximum number of files
compress bool // whether old versions of log files are compressed
lastTimestamp time.Time // timestamp of the last log
filesRefCounter refCounter // keep reference-counted of decompressed files
notifyReaders *pubsub.Publisher
marshal logger.MarshalFunc
createDecoder MakeDecoderFn
getTailReader GetTailReaderFunc
perms os.FileMode
}
// MakeDecoderFn creates a decoder
type MakeDecoderFn func(rdr io.Reader) Decoder
// Decoder is for reading logs
// It is created by the log reader by calling the `MakeDecoderFunc`
type Decoder interface {
// Reset resets the decoder
// Reset is called for certain events, such as log rotations
Reset(io.Reader)
// Decode decodes the next log messeage from the stream
Decode() (*logger.Message, error)
// Close signals to the decoder that it can release whatever resources it was using.
Close()
}
// SizeReaderAt defines a ReaderAt that also reports its size.
// This is used for tailing log files.
type SizeReaderAt interface {
io.ReaderAt
Size() int64
}
// GetTailReaderFunc is used to truncate a reader to only read as much as is required
// in order to get the passed in number of log lines.
// It returns the sectioned reader, the number of lines that the section reader
// contains, and any error that occurs.
type GetTailReaderFunc func(ctx context.Context, f SizeReaderAt, nLogLines int) (rdr io.Reader, nLines int, err error)
// NewLogFile creates new LogFile
func NewLogFile(logPath string, capacity int64, maxFiles int, compress bool, marshaller logger.MarshalFunc, decodeFunc MakeDecoderFn, perms os.FileMode, getTailReader GetTailReaderFunc) (*LogFile, error) {
log, err := openFile(logPath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, perms)
if err != nil {
return nil, err
}
size, err := log.Seek(0, io.SeekEnd)
if err != nil {
return nil, err
}
return &LogFile{
f: log,
capacity: capacity,
currentSize: size,
maxFiles: maxFiles,
compress: compress,
filesRefCounter: refCounter{counter: make(map[string]int)},
notifyReaders: pubsub.NewPublisher(0, 1),
marshal: marshaller,
createDecoder: decodeFunc,
perms: perms,
getTailReader: getTailReader,
}, nil
}
// WriteLogEntry writes the provided log message to the current log file.
// This may trigger a rotation event if the max file/capacity limits are hit.
func (w *LogFile) WriteLogEntry(msg *logger.Message) error {
b, err := w.marshal(msg)
if err != nil {
return errors.Wrap(err, "error marshalling log message")
}
logger.PutMessage(msg)
w.mu.Lock()
if w.closed {
w.mu.Unlock()
return errors.New("cannot write because the output file was closed")
}
if err := w.checkCapacityAndRotate(); err != nil {
w.mu.Unlock()
return errors.Wrap(err, "error rotating log file")
}
n, err := w.f.Write(b)
if err == nil {
w.currentSize += int64(n)
w.lastTimestamp = msg.Timestamp
}
w.mu.Unlock()
return errors.Wrap(err, "error writing log entry")
}
func (w *LogFile) checkCapacityAndRotate() (retErr error) {
if w.capacity == -1 {
return nil
}
if w.currentSize < w.capacity {
return nil
}
w.rotateMu.Lock()
noCompress := w.maxFiles <= 1 || !w.compress
defer func() {
// If we aren't going to run the goroutine to compress the log file, then we need to unlock in this function.
// Otherwise the lock will be released in the goroutine that handles compression.
if retErr != nil || noCompress {
w.rotateMu.Unlock()
}
}()
fname := w.f.Name()
if err := w.f.Close(); err != nil {
// if there was an error during a prior rotate, the file could already be closed
if !errors.Is(err, os.ErrClosed) {
return errors.Wrap(err, "error closing file")
}
}
if err := rotate(fname, w.maxFiles, w.compress); err != nil {
logrus.WithError(err).Warn("Error rotating log file, log data may have been lost")
} else {
var renameErr error
for i := 0; i < 10; i++ {
if renameErr = os.Rename(fname, fname+".1"); renameErr != nil && !os.IsNotExist(renameErr) {
logrus.WithError(renameErr).WithField("file", fname).Debug("Error rotating current container log file, evicting readers and retrying")
w.notifyReaders.Publish(renameErr)
time.Sleep(100 * time.Millisecond)
continue
}
break
}
if renameErr != nil {
logrus.WithError(renameErr).Error("Error renaming current log file")
}
}
file, err := openFile(fname, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, w.perms)
if err != nil {
return err
}
w.f = file
w.currentSize = 0
w.notifyReaders.Publish(struct{}{})
if noCompress {
return nil
}
ts := w.lastTimestamp
go func() {
if err := compressFile(fname+".1", ts); err != nil {
logrus.WithError(err).Error("Error compressing log file after rotation")
}
w.rotateMu.Unlock()
}()
return nil
}
func rotate(name string, maxFiles int, compress bool) error {
if maxFiles < 2 {
return nil
}
var extension string
if compress {
extension = ".gz"
}
lastFile := fmt.Sprintf("%s.%d%s", name, maxFiles-1, extension)
err := os.Remove(lastFile)
if err != nil && !os.IsNotExist(err) {
return errors.Wrap(err, "error removing oldest log file")
}
for i := maxFiles - 1; i > 1; i-- {
toPath := name + "." + strconv.Itoa(i) + extension
fromPath := name + "." + strconv.Itoa(i-1) + extension
logrus.WithField("source", fromPath).WithField("target", toPath).Trace("Rotating log file")
if err := os.Rename(fromPath, toPath); err != nil && !os.IsNotExist(err) {
return err
}
}
return nil
}
func compressFile(fileName string, lastTimestamp time.Time) (retErr error) {
file, err := open(fileName)
if err != nil {
if os.IsNotExist(err) {
logrus.WithField("file", fileName).WithError(err).Debug("Could not open log file to compress")
return nil
}
return errors.Wrap(err, "failed to open log file")
}
defer func() {
file.Close()
if retErr == nil {
err := os.Remove(fileName)
if err != nil && !os.IsNotExist(err) {
retErr = errors.Wrap(err, "failed to remove source log file")
}
}
}()
outFile, err := openFile(fileName+".gz", os.O_CREATE|os.O_TRUNC|os.O_RDWR, 0640)
if err != nil {
return errors.Wrap(err, "failed to open or create gzip log file")
}
defer func() {
outFile.Close()
if retErr != nil {
if err := os.Remove(fileName + ".gz"); err != nil && !os.IsExist(err) {
logrus.WithError(err).Error("Error cleaning up after failed log compression")
}
}
}()
compressWriter := gzip.NewWriter(outFile)
defer compressWriter.Close()
// Add the last log entry timestamp to the gzip header
extra := rotateFileMetadata{}
extra.LastTime = lastTimestamp
compressWriter.Header.Extra, err = json.Marshal(&extra)
if err != nil {
// Here log the error only and don't return since this is just an optimization.
logrus.Warningf("Failed to marshal gzip header as JSON: %v", err)
}
_, err = pools.Copy(compressWriter, file)
if err != nil {
return errors.Wrapf(err, "error compressing log file %s", fileName)
}
return nil
}
// MaxFiles return maximum number of files
func (w *LogFile) MaxFiles() int {
return w.maxFiles
}
// Close closes underlying file and signals all readers to stop.
func (w *LogFile) Close() error {
w.mu.Lock()
defer w.mu.Unlock()
if w.closed {
return nil
}
if err := w.f.Close(); err != nil && !errors.Is(err, os.ErrClosed) {
return err
}
w.closed = true
return nil
}
// ReadLogs decodes entries from log files and sends them the passed in watcher
//
// Note: Using the follow option can become inconsistent in cases with very frequent rotations and max log files is 1.
// TODO: Consider a different implementation which can effectively follow logs under frequent rotations.
func (w *LogFile) ReadLogs(config logger.ReadConfig, watcher *logger.LogWatcher) {
w.mu.RLock()
currentFile, err := open(w.f.Name())
if err != nil {
w.mu.RUnlock()
watcher.Err <- err
return
}
defer currentFile.Close()
dec := w.createDecoder(nil)
defer dec.Close()
currentChunk, err := newSectionReader(currentFile)
if err != nil {
w.mu.RUnlock()
watcher.Err <- err
return
}
notifyEvict := w.notifyReaders.SubscribeTopicWithBuffer(func(i interface{}) bool {
_, ok := i.(error)
return ok
}, 1)
defer w.notifyReaders.Evict(notifyEvict)
if config.Tail != 0 {
// TODO(@cpuguy83): Instead of opening every file, only get the files which
// are needed to tail.
// This is especially costly when compression is enabled.
files, err := w.openRotatedFiles(config)
w.mu.RUnlock()
if err != nil {
watcher.Err <- err
return
}
closeFiles := func() {
for _, f := range files {
f.Close()
fileName := f.Name()
if strings.HasSuffix(fileName, tmpLogfileSuffix) {
err := w.filesRefCounter.Dereference(fileName)
if err != nil {
logrus.WithError(err).WithField("file", fileName).Error("Failed to dereference the log file")
}
}
}
}
readers := make([]SizeReaderAt, 0, len(files)+1)
for _, f := range files {
stat, err := f.Stat()
if err != nil {
watcher.Err <- errors.Wrap(err, "error reading size of rotated file")
closeFiles()
return
}
readers = append(readers, io.NewSectionReader(f, 0, stat.Size()))
}
if currentChunk.Size() > 0 {
readers = append(readers, currentChunk)
}
ok := tailFiles(readers, watcher, dec, w.getTailReader, config, notifyEvict)
closeFiles()
if !ok {
return
}
w.mu.RLock()
}
if !config.Follow || w.closed {
w.mu.RUnlock()
return
}
w.mu.RUnlock()
notifyRotate := w.notifyReaders.SubscribeTopic(func(i interface{}) bool {
_, ok := i.(struct{})
return ok
})
defer w.notifyReaders.Evict(notifyRotate)
followLogs(currentFile, watcher, notifyRotate, notifyEvict, dec, config.Since, config.Until)
}
func (w *LogFile) openRotatedFiles(config logger.ReadConfig) (files []*os.File, err error) {
w.rotateMu.Lock()
defer w.rotateMu.Unlock()
defer func() {
if err == nil {
return
}
for _, f := range files {
f.Close()
if strings.HasSuffix(f.Name(), tmpLogfileSuffix) {
err := os.Remove(f.Name())
if err != nil && !os.IsNotExist(err) {
logrus.Warnf("Failed to remove logfile: %v", err)
}
}
}
}()
for i := w.maxFiles; i > 1; i-- {
f, err := open(fmt.Sprintf("%s.%d", w.f.Name(), i-1))
if err != nil {
if !os.IsNotExist(err) {
return nil, errors.Wrap(err, "error opening rotated log file")
}
fileName := fmt.Sprintf("%s.%d.gz", w.f.Name(), i-1)
decompressedFileName := fileName + tmpLogfileSuffix
tmpFile, err := w.filesRefCounter.GetReference(decompressedFileName, func(refFileName string, exists bool) (*os.File, error) {
if exists {
return open(refFileName)
}
return decompressfile(fileName, refFileName, config.Since)
})
if err != nil {
if !errors.Is(err, os.ErrNotExist) {
return nil, errors.Wrap(err, "error getting reference to decompressed log file")
}
continue
}
if tmpFile == nil {
// The log before `config.Since` does not need to read
break
}
files = append(files, tmpFile)
continue
}
files = append(files, f)
}
return files, nil
}
func decompressfile(fileName, destFileName string, since time.Time) (*os.File, error) {
cf, err := open(fileName)
if err != nil {
return nil, errors.Wrap(err, "error opening file for decompression")
}
defer cf.Close()
rc, err := gzip.NewReader(cf)
if err != nil {
return nil, errors.Wrap(err, "error making gzip reader for compressed log file")
}
defer rc.Close()
// Extract the last log entry timestramp from the gzip header
extra := &rotateFileMetadata{}
err = json.Unmarshal(rc.Header.Extra, extra)
if err == nil && extra.LastTime.Before(since) {
return nil, nil
}
rs, err := openFile(destFileName, os.O_CREATE|os.O_RDWR, 0640)
if err != nil {
return nil, errors.Wrap(err, "error creating file for copying decompressed log stream")
}
_, err = pools.Copy(rs, rc)
if err != nil {
rs.Close()
rErr := os.Remove(rs.Name())
if rErr != nil && !os.IsNotExist(rErr) {
logrus.Errorf("Failed to remove logfile: %v", rErr)
}
return nil, errors.Wrap(err, "error while copying decompressed log stream to file")
}
return rs, nil
}
func newSectionReader(f *os.File) (*io.SectionReader, error) {
// seek to the end to get the size
// we'll leave this at the end of the file since section reader does not advance the reader
size, err := f.Seek(0, io.SeekEnd)
if err != nil {
return nil, errors.Wrap(err, "error getting current file size")
}
return io.NewSectionReader(f, 0, size), nil
}
func tailFiles(files []SizeReaderAt, watcher *logger.LogWatcher, dec Decoder, getTailReader GetTailReaderFunc, config logger.ReadConfig, notifyEvict <-chan interface{}) (cont bool) {
nLines := config.Tail
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
cont = true
// TODO(@cpuguy83): we should plumb a context through instead of dealing with `WatchClose()` here.
go func() {
select {
case err := <-notifyEvict:
if err != nil {
watcher.Err <- err.(error)
cont = false
cancel()
}
case <-ctx.Done():
case <-watcher.WatchConsumerGone():
cont = false
cancel()
}
}()
readers := make([]io.Reader, 0, len(files))
if config.Tail > 0 {
for i := len(files) - 1; i >= 0 && nLines > 0; i-- {
tail, n, err := getTailReader(ctx, files[i], nLines)
if err != nil {
watcher.Err <- errors.Wrap(err, "error finding file position to start log tailing")
return
}
nLines -= n
readers = append([]io.Reader{tail}, readers...)
}
} else {
for _, r := range files {
readers = append(readers, &wrappedReaderAt{ReaderAt: r})
}
}
rdr := io.MultiReader(readers...)
dec.Reset(rdr)
for {
msg, err := dec.Decode()
if err != nil {
if !errors.Is(err, io.EOF) {
watcher.Err <- err
}
return
}
if !config.Since.IsZero() && msg.Timestamp.Before(config.Since) {
continue
}
if !config.Until.IsZero() && msg.Timestamp.After(config.Until) {
return
}
select {
case <-ctx.Done():
return
case watcher.Msg <- msg:
}
}
}
func watchFile(name string) (filenotify.FileWatcher, error) {
var fileWatcher filenotify.FileWatcher
if runtime.GOOS == "windows" {
// FileWatcher on Windows files is based on the syscall notifications which has an issue because of file caching.
// It is based on ReadDirectoryChangesW() which doesn't detect writes to the cache. It detects writes to disk only.
// Because of the OS lazy writing, we don't get notifications for file writes and thereby the watcher
// doesn't work. Hence for Windows we will use poll based notifier.
fileWatcher = filenotify.NewPollingWatcher()
} else {
var err error
fileWatcher, err = filenotify.New()
if err != nil {
return nil, err
}
}
logger := logrus.WithFields(logrus.Fields{
"module": "logger",
"file": name,
})
if err := fileWatcher.Add(name); err != nil {
// we will retry using file poller.
logger.WithError(err).Warnf("falling back to file poller")
fileWatcher.Close()
fileWatcher = filenotify.NewPollingWatcher()
if err := fileWatcher.Add(name); err != nil {
fileWatcher.Close()
logger.WithError(err).Debugf("error watching log file for modifications")
return nil, err
}
}
return fileWatcher, nil
}
type wrappedReaderAt struct {
io.ReaderAt
pos int64
}
func (r *wrappedReaderAt) Read(p []byte) (int, error) {
n, err := r.ReaderAt.ReadAt(p, r.pos)
r.pos += int64(n)
return n, err
}