set log format using a flag

pkg/constants/constants.go

@@ -17,9 +17,6 @@ limitations under the License.
 package constants
 
 const (
-	// DefaultLogLevel is the default log level
-	DefaultLogLevel = "info"
-
 	// RootDir is the path to the root directory
 	RootDir = "/"
 

pkg/logging/logging.go

@@ -0,0 +1,76 @@
+/*
+Copyright 2020 Google LLC
+
+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"
+
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"github.com/spf13/pflag"
+)
+
+const (
+	// Default log level
+	DefaultLevel = "info"
+
+	// Text format
+	FormatText = "text"
+	// Colored text format
+	FormatColor = "color"
+	// JSON format
+	FormatJSON = "json"
+)
+
+var (
+	logLevel  string
+	logFormat string
+)
+
+// AddFlags injects logging-related flags into the given FlagSet
+func AddFlags(fs *pflag.FlagSet) {
+	fs.StringVarP(&logLevel, "verbosity", "v", DefaultLevel, "Log level (debug, info, warn, error, fatal, panic")
+	fs.StringVar(&logFormat, "log-format", FormatColor, "Log format (text, color, json)")
+}
+
+// Configure sets the logrus logging level and formatter
+func Configure() error {
+	lvl, err := logrus.ParseLevel(logLevel)
+	if err != nil {
+		return errors.Wrap(err, "parsing log level")
+	}
+	logrus.SetLevel(lvl)
+
+	var formatter logrus.Formatter
+	switch logFormat {
+	case FormatText:
+		formatter = &logrus.TextFormatter{
+			DisableColors: true,
+		}
+	case FormatColor:
+		formatter = &logrus.TextFormatter{
+			ForceColors: true,
+		}
+	case FormatJSON:
+		formatter = &logrus.JSONFormatter{}
+	default:
+		return fmt.Errorf("not a valid log format: %q. Please specify one of (text, color, json)", logFormat)
+	}
+	logrus.SetFormatter(formatter)
+
+	return nil
+}

pkg/util/util.go

@@ -28,25 +28,10 @@ import (
 	"syscall"
 
 	"github.com/minio/highwayhash"
-	"github.com/pkg/errors"
-	"github.com/sirupsen/logrus"
 
 	v1 "github.com/google/go-containerregistry/pkg/v1"
 )
 
-// ConfigureLogging sets the logrus logging level and forces logs to be colorful (!)
-func ConfigureLogging(logLevel string) error {
-	lvl, err := logrus.ParseLevel(logLevel)
-	if err != nil {
-		return errors.Wrap(err, "parsing log level")
-	}
-	logrus.SetLevel(lvl)
-	logrus.SetFormatter(&logrus.TextFormatter{
-		ForceColors: true,
-	})
-	return nil
-}
-
 // Hasher returns a hash function, used in snapshotting to determine if a file has changed
 func Hasher() func(string) (string, error) {
 	pool := sync.Pool{