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