backends can be reopened

backend.go

@@ -14,6 +14,7 @@ type Backend interface {
 	SetFormatter(*Formatter)
 	SetLevel(Level)
 	Level() Level
+	Reopen() error
 }
 
 //
@@ -24,6 +25,7 @@ type FileBackend struct {
 	l         io.Writer
 	formatter *Formatter
 	level     Level
+	filepath  string
 }
 
 // Creates a new backend to write the logs on the standard output
@@ -53,6 +55,7 @@ func NewFileBackend(filename string) (b *FileBackend, e error) {
 	b = &FileBackend{
 		l:         filename_fd,
 		formatter: &defaultFormatter,
+		filepath:  filename,
 	}
 	return
 }
@@ -83,6 +86,20 @@ func (b *FileBackend) SetFormatter(f *Formatter) {
 	b.formatter = f
 }
 
+func (b *FileBackend) Reopen() error {
+	if b.filepath == "" {
+		return nil
+	}
+
+	filename_fd, err := os.OpenFile(b.filepath, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0644)
+	if err != nil {
+		return errors.New(fmt.Sprintf("Cannot open log file %s (%s)", b.filepath, err.Error()))
+	} else {
+		b.l = filename_fd
+	}
+	return nil
+}
+
 //
 // Syslog Backend
 //
@@ -140,6 +157,10 @@ func (sb *SyslogBackend) Level() Level {
 	return sb.level
 }
 
+func (sb *SyslogBackend) Reopen() error {
+	return nil
+}
+
 var facilities = map[string]syslog.Priority{
 	"kern":     syslog.LOG_KERN,
 	"user":     syslog.LOG_USER,
@@ -192,3 +213,7 @@ func (nb *NoopBackend) SetLevel(level Level) {}
 func (nb *NoopBackend) Level() Level {
 	return FATAL
 }
+
+func (nb *NoopBackend) Reopen() error {
+	return nil
+}