Add logging feature for debug

This diff adds logging feature for debug.

logging/logging.go

@@ -0,0 +1,130 @@
+// Copyright (c) 2018 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package logging
+
+import (
+	"fmt"
+	"os"
+	"strings"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+// Level type
+type Level uint32
+
+const (
+	PanicLevel Level = iota
+	ErrorLevel
+	DebugLevel
+	MaxLevel
+	UnknownLevel
+)
+
+var loggingStderr bool
+var loggingFp	*os.File
+var loggingLevel Level
+const defaultTimestampFormat = time.RFC3339
+
+func (l Level) String() string {
+	switch l {
+	case PanicLevel:
+		return "panic"
+	case ErrorLevel:
+		return "error"
+	case DebugLevel:
+		return "debug"
+	}
+	return "unknown"
+}
+
+func Printf(level Level, format string, a ...interface{}) {
+	header := "%s [%s] "
+	t := time.Now()
+	if level > loggingLevel {
+		return
+	}
+
+	if loggingStderr {
+		fmt.Fprintf(os.Stderr, header, t.Format(defaultTimestampFormat), level)
+		fmt.Fprintf(os.Stderr, format, a...)
+		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")
+	}
+}
+
+func Debugf(format string, a ...interface{}) {
+	Printf(DebugLevel, format, a...)
+}
+
+func Errorf(format string, a ...interface{}) {
+	Printf(ErrorLevel, format, a...)
+}
+
+func Panicf(format string, a ...interface{}) {
+	Printf(PanicLevel, format, a...)
+	Printf(PanicLevel, "========= Stack trace output ========")
+	Printf(PanicLevel, "%+v", errors.New("Multus Panic"))
+	Printf(PanicLevel, "========= Stack trace output end ========")
+}
+
+func GetLoggingLevel (levelStr string) Level {
+	switch strings.ToLower(levelStr) {
+	case "debug":
+		return DebugLevel
+	case "error":
+		return ErrorLevel
+	case "panic":
+		return PanicLevel
+	}
+	fmt.Fprintf(os.Stderr, "multus logging: cannot set logging level to %s\n", levelStr)
+	return UnknownLevel
+}
+
+func SetLogLevel (levelStr string) {
+	level := GetLoggingLevel(levelStr)
+	if level < MaxLevel {
+		loggingLevel = level
+	}
+}
+
+func SetLogStderr (enable bool) {
+	loggingStderr = enable
+}
+
+func SetLogFile (filename string) {
+	if filename == "" {
+		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
+}
+
+func init() {
+	loggingStderr = false
+	loggingFp = nil
+	loggingLevel = PanicLevel
+}