Add log rotator

logrotate/logrotate.go

@@ -0,0 +1,59 @@
+// File wrapper for rotating log files
+// Copied from https://stackoverflow.com/a/28797984
+package logrotate
+
+import (
+	"os"
+	"sync"
+	"time"
+)
+
+type RotateWriter struct {
+	lock     sync.Mutex
+	filename string // should be set to the actual filename
+	fp       *os.File
+}
+
+// Make a new RotateWriter. Return nil if error occurs during setup.
+func New(filename string) *RotateWriter {
+	w := &RotateWriter{filename: filename}
+	err := w.Rotate()
+	if err != nil {
+		return nil
+	}
+	return w
+}
+
+// Write satisfies the io.Writer interface.
+func (w *RotateWriter) Write(output []byte) (int, error) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+	return w.fp.Write(output)
+}
+
+// Perform the actual act of rotating and reopening file.
+func (w *RotateWriter) Rotate() (err error) {
+	w.lock.Lock()
+	defer w.lock.Unlock()
+
+	// Close existing file if open
+	if w.fp != nil {
+		err = w.fp.Close()
+		w.fp = nil
+		if err != nil {
+			return
+		}
+	}
+	// Rename dest file if it already exists
+	_, err = os.Stat(w.filename)
+	if err == nil {
+		err = os.Rename(w.filename, w.filename+"."+time.Now().Format(time.RFC3339))
+		if err != nil {
+			return
+		}
+	}
+
+	// Create a file.
+	w.fp, err = os.Create(w.filename)
+	return
+}