/
logfile.go
654 lines (579 loc) · 18 KB
/
logfile.go
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package loggerutils // import "github.com/docker/docker/daemon/logger/loggerutils"
import (
"compress/gzip"
"context"
"encoding/json"
"fmt"
"io"
"io/fs"
"math"
"os"
"strconv"
"sync"
"time"
"github.com/containerd/log"
"github.com/docker/docker/daemon/logger"
"github.com/docker/docker/pkg/pools"
"github.com/pkg/errors"
)
// rotateFileMetadata is a metadata of the gzip header of the compressed log file
type rotateFileMetadata struct {
LastTime time.Time `json:"lastTime,omitempty"`
}
// LogFile is Logger implementation for default Docker logging.
type LogFile struct {
mu sync.Mutex // protects the logfile access
closed chan struct{}
rotateMu sync.Mutex // blocks the next rotation until the current rotation is completed
// Lock out readers while performing a non-atomic sequence of filesystem
// operations (RLock: open, Lock: rename, delete).
//
// fsopMu should be locked for writing only while holding rotateMu.
fsopMu sync.RWMutex
// Logger configuration
capacity int64 // maximum size of each file
maxFiles int // maximum number of files
compress bool // whether old versions of log files are compressed
perms os.FileMode
// Log file codec
createDecoder MakeDecoderFn
getTailReader GetTailReaderFunc
// Log reader state in a 1-buffered channel.
//
// Share memory by communicating: receive to acquire, send to release.
// The state struct is passed around by value so that use-after-send
// bugs cannot escalate to data races.
//
// A method which receives the state value takes ownership of it. The
// owner is responsible for either passing ownership along or sending
// the state back to the channel. By convention, the semantics of
// passing along ownership is expressed with function argument types.
// Methods which take a pointer *logReadState argument borrow the state,
// analogous to functions which require a lock to be held when calling.
// The caller retains ownership. Calling a method which takes a
// value logFileState argument gives ownership to the callee.
read chan logReadState
decompress *sharedTempFileConverter
pos logPos // Current log file write position.
f *os.File // Current log file for writing.
lastTimestamp time.Time // timestamp of the last log
}
type logPos struct {
// Size of the current file.
size int64
// File rotation sequence number (modulo 2**16).
rotation uint16
}
type logReadState struct {
// Current log file position.
pos logPos
// Wait list to be notified of the value of pos next time it changes.
wait []chan<- logPos
}
// 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.Reader
io.ReaderAt
Size() int64
}
type readAtCloser interface {
io.ReaderAt
io.Closer
}
// 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, 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
}
pos := logPos{
size: size,
// Force a wraparound on first rotation to shake out any
// modular-arithmetic bugs.
rotation: math.MaxUint16,
}
st := make(chan logReadState, 1)
st <- logReadState{pos: pos}
return &LogFile{
f: log,
read: st,
pos: pos,
closed: make(chan struct{}),
capacity: capacity,
maxFiles: maxFiles,
compress: compress,
decompress: newSharedTempFileConverter(decompress),
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(timestamp time.Time, marshalled []byte) error {
select {
case <-w.closed:
return errors.New("cannot write because the output file was closed")
default:
}
w.mu.Lock()
defer w.mu.Unlock()
// Are we due for a rotation?
if w.capacity != -1 && w.pos.size >= w.capacity {
if err := w.rotate(); err != nil {
return errors.Wrap(err, "error rotating log file")
}
}
n, err := w.f.Write(marshalled)
if err != nil {
return errors.Wrap(err, "error writing log entry")
}
w.pos.size += int64(n)
w.lastTimestamp = timestamp
// Notify any waiting readers that there is a new log entry to read.
st := <-w.read
defer func() { w.read <- st }()
st.pos = w.pos
for _, c := range st.wait {
c <- st.pos
}
// Optimization: retain the backing array to save a heap allocation next
// time a reader appends to the list.
if st.wait != nil {
st.wait = st.wait[:0]
}
return nil
}
func (w *LogFile) rotate() (retErr error) {
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, fs.ErrClosed) {
return errors.Wrap(err, "error closing file")
}
}
file, err := func() (*os.File, error) {
w.fsopMu.Lock()
defer w.fsopMu.Unlock()
if err := rotate(fname, w.maxFiles, w.compress); err != nil {
log.G(context.TODO()).WithError(err).Warn("Error rotating log file, log data may have been lost")
} else {
// We may have readers working their way through the
// current log file so we can't truncate it. We need to
// start writing new logs to an empty file with the same
// name as the current one so we need to rotate the
// current file out of the way.
if w.maxFiles < 2 {
if err := unlink(fname); err != nil && !errors.Is(err, fs.ErrNotExist) {
log.G(context.TODO()).WithError(err).Error("Error unlinking current log file")
}
} else {
if err := os.Rename(fname, fname+".1"); err != nil && !errors.Is(err, fs.ErrNotExist) {
log.G(context.TODO()).WithError(err).Error("Error renaming current log file")
}
}
}
// Notwithstanding the above, open with the truncate flag anyway
// in case rotation didn't work out as planned.
return openFile(fname, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, w.perms)
}()
if err != nil {
return err
}
w.f = file
w.pos = logPos{rotation: w.pos.rotation + 1}
if noCompress {
return nil
}
ts := w.lastTimestamp
go func() {
defer w.rotateMu.Unlock()
// No need to hold fsopMu as at no point will the filesystem be
// in a state which would cause problems for readers. Opening
// the uncompressed file is tried first, falling back to the
// compressed one. compressFile only deletes the uncompressed
// file once the compressed one is fully written out, so at no
// point during the compression process will a reader fail to
// open a complete copy of the file.
if err := compressFile(fname+".1", ts); err != nil {
log.G(context.TODO()).WithError(err).Error("Error compressing log file after rotation")
}
}()
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 := unlink(lastFile)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
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
err := os.Rename(fromPath, toPath)
log.G(context.TODO()).WithError(err).WithField("source", fromPath).WithField("target", toPath).Trace("Rotating log file")
if err != nil && !errors.Is(err, fs.ErrNotExist) {
return err
}
}
return nil
}
func compressFile(fileName string, lastTimestamp time.Time) (retErr error) {
file, err := open(fileName)
if err != nil {
if errors.Is(err, fs.ErrNotExist) {
log.G(context.TODO()).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 := unlink(fileName)
if err != nil && !errors.Is(err, fs.ErrNotExist) {
retErr = errors.Wrap(err, "failed to remove source log file")
}
}
}()
outFile, err := openFile(fileName+".gz", os.O_CREATE|os.O_TRUNC|os.O_RDWR, 0o640)
if err != nil {
return errors.Wrap(err, "failed to open or create gzip log file")
}
defer func() {
outFile.Close()
if retErr != nil {
if err := unlink(fileName + ".gz"); err != nil && !errors.Is(err, fs.ErrNotExist) {
log.G(context.TODO()).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.
log.G(context.TODO()).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()
select {
case <-w.closed:
return nil
default:
}
if err := w.f.Close(); err != nil && !errors.Is(err, fs.ErrClosed) {
return err
}
close(w.closed)
// Wait until any in-progress rotation is complete.
w.rotateMu.Lock()
w.rotateMu.Unlock() //nolint:staticcheck
return nil
}
// ReadLogs decodes entries from log files.
//
// It is the caller's responsibility to call ConsumerGone on the LogWatcher.
func (w *LogFile) ReadLogs(config logger.ReadConfig) *logger.LogWatcher {
watcher := logger.NewLogWatcher()
// Lock out filesystem operations so that we can capture the read
// position and atomically open the corresponding log file, without the
// file getting rotated out from under us.
w.fsopMu.RLock()
// Capture the read position synchronously to ensure that we start
// following from the last entry logged before ReadLogs was called,
// which is required for flake-free unit testing.
st := <-w.read
pos := st.pos
w.read <- st
go w.readLogsLocked(pos, config, watcher)
return watcher
}
// readLogsLocked is the bulk of the implementation of ReadLogs.
//
// w.fsopMu must be locked for reading when calling this method.
// w.fsopMu.RUnlock() is called before returning.
func (w *LogFile) readLogsLocked(currentPos logPos, config logger.ReadConfig, watcher *logger.LogWatcher) {
defer close(watcher.Msg)
currentFile, err := open(w.f.Name())
if err != nil {
watcher.Err <- err
return
}
defer currentFile.Close()
dec := w.createDecoder(nil)
defer dec.Close()
currentChunk := io.NewSectionReader(currentFile, 0, currentPos.size)
fwd := newForwarder(config)
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)
if err != nil {
watcher.Err <- err
return
}
closeFiles := func() {
for _, f := range files {
f.Close()
}
}
readers := make([]SizeReaderAt, 0, len(files)+1)
for _, f := range files {
switch ff := f.(type) {
case SizeReaderAt:
readers = append(readers, ff)
case interface{ Stat() (fs.FileInfo, error) }:
stat, err := ff.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()))
default:
panic(fmt.Errorf("rotated file value %#v (%[1]T) has neither Size() nor Stat() methods", f))
}
}
if currentChunk.Size() > 0 {
readers = append(readers, currentChunk)
}
ok := tailFiles(readers, watcher, dec, w.getTailReader, config.Tail, fwd)
closeFiles()
if !ok {
return
}
} else {
w.fsopMu.RUnlock()
}
if !config.Follow {
return
}
(&follow{
LogFile: w,
Watcher: watcher,
Decoder: dec,
Forwarder: fwd,
}).Do(currentFile, currentPos)
}
// openRotatedFiles returns a slice of files open for reading, in order from
// oldest to newest, and calls w.fsopMu.RUnlock() before returning.
//
// This method must only be called with w.fsopMu locked for reading.
func (w *LogFile) openRotatedFiles(config logger.ReadConfig) (files []readAtCloser, err error) {
type rotatedFile struct {
f *os.File
compressed bool
}
var q []rotatedFile
defer func() {
if err != nil {
for _, qq := range q {
qq.f.Close()
}
for _, f := range files {
f.Close()
}
}
}()
q, err = func() (q []rotatedFile, err error) {
defer w.fsopMu.RUnlock()
q = make([]rotatedFile, 0, w.maxFiles)
for i := w.maxFiles; i > 1; i-- {
var f rotatedFile
f.f, err = open(fmt.Sprintf("%s.%d", w.f.Name(), i-1))
if err != nil {
if !errors.Is(err, fs.ErrNotExist) {
return nil, errors.Wrap(err, "error opening rotated log file")
}
f.compressed = true
f.f, err = open(fmt.Sprintf("%s.%d.gz", w.f.Name(), i-1))
if err != nil {
if !errors.Is(err, fs.ErrNotExist) {
return nil, errors.Wrap(err, "error opening file for decompression")
}
continue
}
}
q = append(q, f)
}
return q, nil
}()
if err != nil {
return nil, err
}
for len(q) > 0 {
qq := q[0]
q = q[1:]
if qq.compressed {
defer qq.f.Close()
f, err := w.maybeDecompressFile(qq.f, config)
if err != nil {
return nil, err
}
if f != nil {
// The log before `config.Since` does not need to read
files = append(files, f)
}
} else {
files = append(files, qq.f)
}
}
return files, nil
}
func (w *LogFile) maybeDecompressFile(cf *os.File, config logger.ReadConfig) (readAtCloser, error) {
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.IsZero() && extra.LastTime.Before(config.Since) {
return nil, nil
}
tmpf, err := w.decompress.Do(cf)
return tmpf, errors.Wrap(err, "error decompressing log file")
}
func decompress(dst io.WriteSeeker, src io.ReadSeeker) error {
if _, err := src.Seek(0, io.SeekStart); err != nil {
return err
}
rc, err := gzip.NewReader(src)
if err != nil {
return err
}
_, err = pools.Copy(dst, rc)
if err != nil {
return err
}
return rc.Close()
}
func tailFiles(files []SizeReaderAt, watcher *logger.LogWatcher, dec Decoder, getTailReader GetTailReaderFunc, nLines int, fwd *forwarder) (cont bool) {
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 <-ctx.Done():
case <-watcher.WatchConsumerGone():
cancel()
}
}()
readers := make([]io.Reader, 0, len(files))
if nLines > 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 false
}
nLines -= n
readers = append([]io.Reader{tail}, readers...)
}
} else {
for _, r := range files {
readers = append(readers, r)
}
}
rdr := io.MultiReader(readers...)
dec.Reset(rdr)
return fwd.Do(watcher, dec)
}
type forwarder struct {
since, until time.Time
}
func newForwarder(config logger.ReadConfig) *forwarder {
return &forwarder{since: config.Since, until: config.Until}
}
// Do reads log messages from dec and sends the messages matching the filter
// conditions to watcher. Do returns cont=true iff it has read all messages from
// dec without encountering a message with a timestamp which is after the
// configured until time.
func (fwd *forwarder) Do(watcher *logger.LogWatcher, dec Decoder) (cont bool) {
for {
msg, err := dec.Decode()
if err != nil {
if errors.Is(err, io.EOF) {
return true
}
watcher.Err <- err
return false
}
if !fwd.since.IsZero() {
if msg.Timestamp.Before(fwd.since) {
continue
}
// We've found our first message with a timestamp >= since. As message
// timestamps might not be monotonic, we need to skip the since check for all
// subsequent messages so we do not filter out later messages which happen to
// have timestamps before since.
fwd.since = time.Time{}
}
if !fwd.until.IsZero() && msg.Timestamp.After(fwd.until) {
return false
}
select {
case <-watcher.WatchConsumerGone():
return false
case watcher.Msg <- msg:
}
}
}