// Package lumberjack provides a rolling logger. // // Note that this is v2.0 of lumberjack, and should be imported using gopkg.in // thusly: // // import "gopkg.in/natefinch/lumberjack.v2" // // The package name remains simply lumberjack, and the code resides at // https://github.com/natefinch/lumberjack under the v2.0 branch. // // Lumberjack is intended to be one part of a logging infrastructure. // It is not an all-in-one solution, but instead is a pluggable // component at the bottom of the logging stack that simply controls the files // to which logs are written. // // Lumberjack plays well with any logging package that can write to an // io.Writer, including the standard library's log package. // // Lumberjack assumes that only one process is writing to the output files. // Using the same lumberjack configuration from multiple processes on the same // machine will result in improper behavior. package lumberjack import ( "compress/gzip" "errors" "fmt" "io" "io/ioutil" "os" "path/filepath" "sort" "strings" "sync" "time" ) const ( backupTimeFormat = "2006-01-02T15-04-05.000" compressSuffix = ".gz" defaultMaxSize = 100 ) // ensure we always implement io.WriteCloser var _ io.WriteCloser = (*Logger)(nil) // Logger is an io.WriteCloser that writes to the specified filename. // // Logger opens or creates the logfile on first Write. If the file exists and // is less than MaxSize megabytes, lumberjack will open and append to that file. // If the file exists and its size is >= MaxSize megabytes, the file is renamed // by putting the current time in a timestamp in the name immediately before the // file's extension (or the end of the filename if there's no extension). A new // log file is then created using original filename. // // Whenever a write would cause the current log file exceed MaxSize megabytes, // the current file is closed, renamed, and a new log file created with the // original name. Thus, the filename you give Logger is always the "current" log // file. // // Backups use the log file name given to Logger, in the form // `name-timestamp.ext` where name is the filename without the extension, // timestamp is the time at which the log was rotated formatted with the // time.Time format of `2006-01-02T15-04-05.000` and the extension is the // original extension. For example, if your Logger.Filename is // `/var/log/foo/server.log`, a backup created at 6:30pm on Nov 11 2016 would // use the filename `/var/log/foo/server-2016-11-04T18-30-00.000.log` // // Cleaning Up Old Log Files // // Whenever a new logfile gets created, old log files may be deleted. The most // recent files according to the encoded timestamp will be retained, up to a // number equal to MaxBackups (or all of them if MaxBackups is 0). Any files // with an encoded timestamp older than MaxAge days are deleted, regardless of // MaxBackups. Note that the time encoded in the timestamp is the rotation // time, which may differ from the last time that file was written to. // // If MaxBackups and MaxAge are both 0, no old log files will be deleted. type Logger struct { // Filename is the file to write logs to. Backup log files will be retained // in the same directory. It uses <processname>-lumberjack.log in // os.TempDir() if empty. Filename string `json:"filename" yaml:"filename"` // MaxSize is the maximum size in megabytes of the log file before it gets // rotated. It defaults to 100 megabytes. MaxSize int `json:"maxsize" yaml:"maxsize"` // MaxAge is the maximum number of days to retain old log files based on the // timestamp encoded in their filename. Note that a day is defined as 24 // hours and may not exactly correspond to calendar days due to daylight // savings, leap seconds, etc. The default is not to remove old log files // based on age. MaxAge int `json:"maxage" yaml:"maxage"` // MaxBackups is the maximum number of old log files to retain. The default // is to retain all old log files (though MaxAge may still cause them to get // deleted.) MaxBackups int `json:"maxbackups" yaml:"maxbackups"` // LocalTime determines if the time used for formatting the timestamps in // backup files is the computer's local time. The default is to use UTC // time. LocalTime bool `json:"localtime" yaml:"localtime"` // Compress determines if the rotated log files should be compressed // using gzip. The default is not to perform compression. Compress bool `json:"compress" yaml:"compress"` size int64 file *os.File mu sync.Mutex millCh chan bool startMill sync.Once } var ( // currentTime exists so it can be mocked out by tests. currentTime = time.Now // os_Stat exists so it can be mocked out by tests. os_Stat = os.Stat // megabyte is the conversion factor between MaxSize and bytes. It is a // variable so tests can mock it out and not need to write megabytes of data // to disk. megabyte = 1024 * 1024 ) // Write implements io.Writer. If a write would cause the log file to be larger // than MaxSize, the file is closed, renamed to include a timestamp of the // current time, and a new log file is created using the original log file name. // If the length of the write is greater than MaxSize, an error is returned. func (l *Logger) Write(p []byte) (n int, err error) { l.mu.Lock() defer l.mu.Unlock() writeLen := int64(len(p)) if writeLen > l.max() { return 0, fmt.Errorf( "write length %d exceeds maximum file size %d", writeLen, l.max(), ) } if l.file == nil { if err = l.openExistingOrNew(len(p)); err != nil { return 0, err } } if l.size+writeLen > l.max() { if err := l.rotate(); err != nil { return 0, err } } n, err = l.file.Write(p) l.size += int64(n) return n, err } // Close implements io.Closer, and closes the current logfile. func (l *Logger) Close() error { l.mu.Lock() defer l.mu.Unlock() return l.close() } // close closes the file if it is open. func (l *Logger) close() error { if l.file == nil { return nil } err := l.file.Close() l.file = nil return err } // Rotate causes Logger to close the existing log file and immediately create a // new one. This is a helper function for applications that want to initiate // rotations outside of the normal rotation rules, such as in response to // SIGHUP. After rotating, this initiates compression and removal of old log // files according to the configuration. func (l *Logger) Rotate() error { l.mu.Lock() defer l.mu.Unlock() return l.rotate() } // rotate closes the current file, moves it aside with a timestamp in the name, // (if it exists), opens a new file with the original filename, and then runs // post-rotation processing and removal. func (l *Logger) rotate() error { if err := l.close(); err != nil { return err } if err := l.openNew(); err != nil { return err } l.mill() return nil } // openNew opens a new log file for writing, moving any old log file out of the // way. This methods assumes the file has already been closed. func (l *Logger) openNew() error { err := os.MkdirAll(l.dir(), 0744) if err != nil { return fmt.Errorf("can't make directories for new logfile: %s", err) } name := l.filename() mode := os.FileMode(0644) info, err := os_Stat(name) if err == nil { // Copy the mode off the old logfile. mode = info.Mode() // move the existing file newname := backupName(name, l.LocalTime) if err := os.Rename(name, newname); err != nil { return fmt.Errorf("can't rename log file: %s", err) } // this is a no-op anywhere but linux if err := chown(name, info); err != nil { return err } } // we use truncate here because this should only get called when we've moved // the file ourselves. if someone else creates the file in the meantime, // just wipe out the contents. f, err := os.OpenFile(name, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, mode) if err != nil { return fmt.Errorf("can't open new logfile: %s", err) } l.file = f l.size = 0 return nil } // backupName creates a new filename from the given name, inserting a timestamp // between the filename and the extension, using the local time if requested // (otherwise UTC). func backupName(name string, local bool) string { dir := filepath.Dir(name) filename := filepath.Base(name) ext := filepath.Ext(filename) prefix := filename[:len(filename)-len(ext)] t := currentTime() if !local { t = t.UTC() } timestamp := t.Format(backupTimeFormat) return filepath.Join(dir, fmt.Sprintf("%s-%s%s", prefix, timestamp, ext)) } // openExistingOrNew opens the logfile if it exists and if the current write // would not put it over MaxSize. If there is no such file or the write would // put it over the MaxSize, a new file is created. func (l *Logger) openExistingOrNew(writeLen int) error { l.mill() filename := l.filename() info, err := os_Stat(filename) if os.IsNotExist(err) { return l.openNew() } if err != nil { return fmt.Errorf("error getting log file info: %s", err) } if info.Size()+int64(writeLen) >= l.max() { return l.rotate() } file, err := os.OpenFile(filename, os.O_APPEND|os.O_WRONLY, 0644) if err != nil { // if we fail to open the old log file for some reason, just ignore // it and open a new log file. return l.openNew() } l.file = file l.size = info.Size() return nil } // genFilename generates the name of the logfile from the current time. func (l *Logger) filename() string { if l.Filename != "" { return l.Filename } name := filepath.Base(os.Args[0]) + "-lumberjack.log" return filepath.Join(os.TempDir(), name) } // millRunOnce performs compression and removal of stale log files. // Log files are compressed if enabled via configuration and old log // files are removed, keeping at most l.MaxBackups files, as long as // none of them are older than MaxAge. func (l *Logger) millRunOnce() error { if l.MaxBackups == 0 && l.MaxAge == 0 && !l.Compress { return nil } files, err := l.oldLogFiles() if err != nil { return err } var compress, remove []logInfo if l.MaxBackups > 0 && l.MaxBackups < len(files) { preserved := make(map[string]bool) var remaining []logInfo for _, f := range files { // Only count the uncompressed log file or the // compressed log file, not both. fn := f.Name() if strings.HasSuffix(fn, compressSuffix) { fn = fn[:len(fn)-len(compressSuffix)] } preserved[fn] = true if len(preserved) > l.MaxBackups { remove = append(remove, f) } else { remaining = append(remaining, f) } } files = remaining } if l.MaxAge > 0 { diff := time.Duration(int64(24*time.Hour) * int64(l.MaxAge)) cutoff := currentTime().Add(-1 * diff) var remaining []logInfo for _, f := range files { if f.timestamp.Before(cutoff) { remove = append(remove, f) } else { remaining = append(remaining, f) } } files = remaining } if l.Compress { for _, f := range files { if !strings.HasSuffix(f.Name(), compressSuffix) { compress = append(compress, f) } } } for _, f := range remove { errRemove := os.Remove(filepath.Join(l.dir(), f.Name())) if err == nil && errRemove != nil { err = errRemove } } for _, f := range compress { fn := filepath.Join(l.dir(), f.Name()) errCompress := compressLogFile(fn, fn+compressSuffix) if err == nil && errCompress != nil { err = errCompress } } return err } // millRun runs in a goroutine to manage post-rotation compression and removal // of old log files. func (l *Logger) millRun() { for _ = range l.millCh { // what am I going to do, log this? _ = l.millRunOnce() } } // mill performs post-rotation compression and removal of stale log files, // starting the mill goroutine if necessary. func (l *Logger) mill() { l.startMill.Do(func() { l.millCh = make(chan bool, 1) go l.millRun() }) select { case l.millCh <- true: default: } } // oldLogFiles returns the list of backup log files stored in the same // directory as the current log file, sorted by ModTime func (l *Logger) oldLogFiles() ([]logInfo, error) { files, err := ioutil.ReadDir(l.dir()) if err != nil { return nil, fmt.Errorf("can't read log file directory: %s", err) } logFiles := []logInfo{} prefix, ext := l.prefixAndExt() for _, f := range files { if f.IsDir() { continue } if t, err := l.timeFromName(f.Name(), prefix, ext); err == nil { logFiles = append(logFiles, logInfo{t, f}) continue } if t, err := l.timeFromName(f.Name(), prefix, ext+compressSuffix); err == nil { logFiles = append(logFiles, logInfo{t, f}) continue } // error parsing means that the suffix at the end was not generated // by lumberjack, and therefore it's not a backup file. } sort.Sort(byFormatTime(logFiles)) return logFiles, nil } // timeFromName extracts the formatted time from the filename by stripping off // the filename's prefix and extension. This prevents someone's filename from // confusing time.parse. func (l *Logger) timeFromName(filename, prefix, ext string) (time.Time, error) { if !strings.HasPrefix(filename, prefix) { return time.Time{}, errors.New("mismatched prefix") } if !strings.HasSuffix(filename, ext) { return time.Time{}, errors.New("mismatched extension") } ts := filename[len(prefix) : len(filename)-len(ext)] return time.Parse(backupTimeFormat, ts) } // max returns the maximum size in bytes of log files before rolling. func (l *Logger) max() int64 { if l.MaxSize == 0 { return int64(defaultMaxSize * megabyte) } return int64(l.MaxSize) * int64(megabyte) } // dir returns the directory for the current filename. func (l *Logger) dir() string { return filepath.Dir(l.filename()) } // prefixAndExt returns the filename part and extension part from the Logger's // filename. func (l *Logger) prefixAndExt() (prefix, ext string) { filename := filepath.Base(l.filename()) ext = filepath.Ext(filename) prefix = filename[:len(filename)-len(ext)] + "-" return prefix, ext } // compressLogFile compresses the given log file, removing the // uncompressed log file if successful. func compressLogFile(src, dst string) (err error) { f, err := os.Open(src) if err != nil { return fmt.Errorf("failed to open log file: %v", err) } defer f.Close() fi, err := os_Stat(src) if err != nil { return fmt.Errorf("failed to stat log file: %v", err) } if err := chown(dst, fi); err != nil { return fmt.Errorf("failed to chown compressed log file: %v", err) } // If this file already exists, we presume it was created by // a previous attempt to compress the log file. gzf, err := os.OpenFile(dst, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, fi.Mode()) if err != nil { return fmt.Errorf("failed to open compressed log file: %v", err) } defer gzf.Close() gz := gzip.NewWriter(gzf) defer func() { if err != nil { os.Remove(dst) err = fmt.Errorf("failed to compress log file: %v", err) } }() if _, err := io.Copy(gz, f); err != nil { return err } if err := gz.Close(); err != nil { return err } if err := gzf.Close(); err != nil { return err } if err := f.Close(); err != nil { return err } if err := os.Remove(src); err != nil { return err } return nil } // logInfo is a convenience struct to return the filename and its embedded // timestamp. type logInfo struct { timestamp time.Time os.FileInfo } // byFormatTime sorts by newest time formatted in the name. type byFormatTime []logInfo func (b byFormatTime) Less(i, j int) bool { return b[i].timestamp.After(b[j].timestamp) } func (b byFormatTime) Swap(i, j int) { b[i], b[j] = b[j], b[i] } func (b byFormatTime) Len() int { return len(b) }