add BackupDir specify

lumberjack.go

@@ -82,6 +82,10 @@ type Logger struct {
 	// os.TempDir() if empty.
 	Filename string `json:"filename" yaml:"filename"`
 
+	// BackupDir is the dir to moving the backup logs to. 
+	// It uses the same directory of Filename if empty.
+	BackupDir string `json:"backupdir" yaml:"backupdir"`
+
 	// 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"`
@@ -218,7 +222,7 @@ func (l *Logger) openNew() error {
 		// Copy the mode off the old logfile.
 		mode = info.Mode()
 		// move the existing file
-		newname := backupName(name, l.LocalTime)
+		newname := backupName(l.bkdir(), name, l.LocalTime)
 		if err := os.Rename(name, newname); err != nil {
 			return fmt.Errorf("can't rename log file: %s", err)
 		}
@@ -244,8 +248,13 @@ func (l *Logger) openNew() error {
 // 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)
+func backupName(bkdir string, name string, local bool) string {
+	var dir string
+	if (bkdir != "") {
+		dir = bkdir
+	} else {
+		dir = filepath.Dir(name)
+	}
 	filename := filepath.Base(name)
 	ext := filepath.Ext(filename)
 	prefix := filename[:len(filename)-len(ext)]
@@ -398,7 +407,7 @@ func (l *Logger) mill() {
 // 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())
+	files, err := ioutil.ReadDir(l.bkdir())
 	if err != nil {
 		return nil, fmt.Errorf("can't read log file directory: %s", err)
 	}
@@ -453,6 +462,12 @@ func (l *Logger) max() int64 {
 func (l *Logger) dir() string {
 	return filepath.Dir(l.filename())
 }
+func (l *Logger) bkdir() string {
+	if (l.BackupDir != "") {
+		return l.BackupDir
+	}
+	return l.dir()
+}
 
 // prefixAndExt returns the filename part and extension part from the Logger's
 // filename.

lumberjack_test.go

@@ -7,10 +7,12 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
+	//"os/signal"
+	//"syscall"
 	"path/filepath"
 	"testing"
 	"time"
-
+	"log"
 	"github.com/BurntSushi/toml"
 	"gopkg.in/yaml.v2"
 )
@@ -814,3 +816,22 @@ func exists(path string, t testing.TB) {
 	_, err := os.Stat(path)
 	assertUp(err == nil, t, 1, "expected file to exist, but got error from os.Stat: %v", err)
 }
+
+
+
+func TestLogger_Rotate(t *testing.T) {
+
+	l := &Logger{
+		Filename: "./t.log",
+		BackupDir: "./bk",
+		MaxSize: 200,
+		MaxBackups: 2,
+	}
+	log.SetOutput(l)
+
+	for i := 0; i <= 1009000; i++ {
+		log.Println(">>>>>>>>>>>>>>>>>>>>")
+	 }
+
+	l.Rotate()
+}

rotate_test.go

@@ -7,11 +7,18 @@ import (
 	"os"
 	"os/signal"
 	"syscall"
+	"testing"
 )
 
 // Example of how to rotate in response to SIGHUP.
-func ExampleLogger_Rotate() {
-	l := &Logger{}
+func TestExampleLogger_Rotate(t *testing.T) {
+
+	t.FailNow()
+	l := &Logger{
+		Filename: "./t.log"
+		BackupDir: "./bk"
+		MaxSize: 200
+	}
 	log.SetOutput(l)
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, syscall.SIGHUP)