Add support for log rotation

When using debug level the log files tends to fill up quickly.
Add support for log rotation using lumberjack, simple and easy to use
log rotation module.

Signed-off-by: Shahar Klein <sklein@nvidia.com>

logging/logging.go

@@ -19,8 +19,10 @@ import (
 	"os"
 	"strings"
 	"time"
+	"io"
 
 	"github.com/pkg/errors"
+	lumberjack "gopkg.in/natefinch/lumberjack.v2"
 )
 
 // Level type
@@ -37,7 +39,7 @@ const (
 )
 
 var loggingStderr bool
-var loggingFp *os.File
+var loggingW io.Writer
 var loggingLevel Level
 
 const defaultTimestampFormat = time.RFC3339
@@ -69,10 +71,10 @@ func printf(level Level, format string, a ...interface{}) {
 		fmt.Fprintf(os.Stderr, "\n")
 	}
 
-	if loggingFp != nil {
-		fmt.Fprintf(loggingFp, header, t.Format(defaultTimestampFormat), level)
-		fmt.Fprintf(loggingFp, format, a...)
-		fmt.Fprintf(loggingFp, "\n")
+	if loggingW != nil {
+		fmt.Fprintf(loggingW, header, t.Format(defaultTimestampFormat), level)
+		fmt.Fprintf(loggingW, format, a...)
+		fmt.Fprintf(loggingW, "\n")
 	}
 }
 
@@ -139,16 +141,18 @@ func SetLogFile(filename string) {
 		return
 	}
 
-	fp, err := os.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_APPEND, 0644)
-	if err != nil {
-		loggingFp = nil
-		fmt.Fprintf(os.Stderr, "multus logging: cannot open %s", filename)
-	}
-	loggingFp = fp
+	loggingW = &lumberjack.Logger{
+                        Filename:   filename,
+                        MaxSize:    100, // megabytes
+                        MaxBackups: 5,
+                        MaxAge:     5, // days
+                        Compress:   true,
+                    }
+
 }
 
 func init() {
 	loggingStderr = true
-	loggingFp = nil
+	loggingW = nil
 	loggingLevel = PanicLevel
 }