log support file & logrotate

 package beego
 
 import (
+	"fmt"
+	"io/ioutil"
 	"log"
 	"os"
+	"path"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
 )
 
-//--------------------
-// LOG LEVEL
-//--------------------
+type FileLogWriter struct {
+	*log.Logger
+	// The opened file
+	filename string
+
+	maxlines          int
+	maxlines_curlines int
+
+	// Rotate at size
+	maxsize         int
+	maxsize_cursize int
+
+	// Rotate daily
+	daily          bool
+	maxday         int64
+	daily_opendate int
+
+	rotate bool
+
+	startLock sync.Mutex //only one log can writer to the file
+}
+
+func NewFileWriter(fname string, rotate bool) *FileLogWriter {
+	w := &FileLogWriter{
+		filename: fname,
+		maxlines: 1000000,
+		maxsize:  1 << 28, //256 MB
+		daily:    true,
+		maxday:   7,
+		rotate:   rotate,
+	}
+	return w
+}
+
+func (w *FileLogWriter) StartLogger() error {
+	if err := w.DoRotate(false); err != nil {
+		return err
+	}
+	return nil
+}
+
+func (w *FileLogWriter) docheck(size int) {
+	w.startLock.Lock()
+	defer w.startLock.Unlock()
+	if (w.maxlines > 0 && w.maxlines_curlines >= w.maxlines) ||
+		(w.maxsize > 0 && w.maxsize_cursize >= w.maxsize) ||
+		(w.daily && time.Now().Day() != w.daily_opendate) {
+		if err := w.DoRotate(true); err != nil {
+			fmt.Fprintf(os.Stderr, "FileLogWriter(%q): %s\n", w.filename, err)
+			return
+		}
+	}
+	w.maxlines_curlines++
+	w.maxsize_cursize += size
+}
+
+func (w *FileLogWriter) Printf(format string, v ...interface{}) {
+	// Perform the write
+	str := fmt.Sprintf(format, v...)
+	n := 24 + len(str) // 24 stand for the length "2013/06/23 21:00:22 [T] "
+
+	w.docheck(n)
+	w.Logger.Printf(format, v...)
+}
+
+func (w *FileLogWriter) DoRotate(rotate bool) error {
+	if rotate {
+		_, err := os.Lstat(w.filename)
+		if err == nil { // file exists
+			// Find the next available number
+			num := 1
+			fname := ""
+			for ; err == nil && num <= 999; num++ {
+				fname = w.filename + fmt.Sprintf(".%s.%03d", time.Now().Format("2006-01-02"), num)
+				_, err = os.Lstat(fname)
+			}
+			// return error if the last file checked still existed
+			if err == nil {
+				return fmt.Errorf("Rotate: Cannot find free log number to rename %s\n", w.filename)
+			}
+
+			// Rename the file to its newfound home
+			err = os.Rename(w.filename, fname)
+			if err != nil {
+				return fmt.Errorf("Rotate: %s\n", err)
+			}
+			go w.deleteOldLog()
+		}
+	}
+
+	// Open the log file
+	fd, err := os.OpenFile(w.filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0660)
+	if err != nil {
+		return err
+	}
+	w.Logger = log.New(fd, "", log.Ldate|log.Ltime)
+	finfo, err := fd.Stat()
+	if err != nil {
+		return fmt.Errorf("get stat err: %s\n", err)
+	}
+	w.maxsize_cursize = int(finfo.Size())
+	w.daily_opendate = time.Now().Day()
+	if finfo.Size() > 0 {
+		content, err := ioutil.ReadAll(fd)
+		if err != nil {
+			//Do something
+		}
+		w.maxlines_curlines = len(strings.Split(string(content), "\n"))
+
+	} else {
+		w.maxlines_curlines = 0
+	}
+	BeeLogger = w
+	return nil
+}
+
+func (w *FileLogWriter) deleteOldLog() {
+	dir := path.Dir(w.filename)
+	filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
+		if !info.IsDir() && info.ModTime().Unix() < (time.Now().Unix()-60*60*24*w.maxday) {
+			os.Remove(path)
+		}
+		return nil
+	})
+}
 
 // Log levels to control the logging output.
 const (
@@ -34,8 +163,29 @@ func SetLevel(l int) {
 	level = l
 }
 
+type IBeeLogger interface {
+	Fatal(v ...interface{})
+	Fatalf(format string, v ...interface{})
+	Fatalln(v ...interface{})
+	Flags() int
+	Output(calldepth int, s string) error
+	Panic(v ...interface{})
+	Panicf(format string, v ...interface{})
+	Panicln(v ...interface{})
+	Prefix() string
+	Print(v ...interface{})
+	Printf(format string, v ...interface{})
+	Println(v ...interface{})
+	SetFlags(flag int)
+	SetPrefix(prefix string)
+}
+
 // logger references the used application logger.
-var BeeLogger = log.New(os.Stdout, "", log.Ldate|log.Ltime)
+var BeeLogger IBeeLogger
+
+func init() {
+	BeeLogger = log.New(os.Stdout, "", log.Ldate|log.Ltime)
+}
 
 // SetLogger sets a new logger.
 func SetLogger(l *log.Logger) {