Add helper for GoogleCloud field mapping (#177)

Author: mschewe

helper.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/sirupsen/logrus"
+
 	"github.com/snabble/go-logging/v2/tracex"
 )
 
@@ -33,8 +34,9 @@ var DefaultLogConfig = LogConfig{
 }
 
 type LogConfig struct {
-	EnableTraces      bool
-	EnableTextLogging bool
+	EnableTraces       bool
+	EnableTextLogging  bool
+	googleCloudLogging bool
 }
 
 // Set creates a new Logger with the matching specification
@@ -43,6 +45,13 @@ func Set(level string, textLogging bool) error {
 	return SetWithConfig(level, config)
 }
 
+// SetGoogle configures the Logger to use GoogleCloud compatible fields in JSON format
+// https://cloud.google.com/logging/docs/structured-logging#structured_logging_special_fields
+func SetGoogle(level string) error {
+	config := &LogConfig{EnableTraces: true, googleCloudLogging: true}
+	return SetWithConfig(level, config)
+}
+
 // SetWithConfig creates a new Logger with the matching specification based on the config, pass nil to use
 // the defaults.
 func SetWithConfig(level string, config *LogConfig) error {
@@ -58,6 +67,15 @@ func SetWithConfig(level string, config *LogConfig) error {
 	logger := logrus.New()
 	if config.EnableTextLogging {
 		logger.Formatter = &logrus.TextFormatter{DisableColors: true}
+	} else if config.googleCloudLogging {
+		logger.Formatter = &logrus.JSONFormatter{
+			FieldMap: logrus.FieldMap{
+				logrus.FieldKeyTime:  "timestamp",
+				logrus.FieldKeyLevel: "severity",
+				logrus.FieldKeyMsg:   "message",
+			},
+			TimestampFormat: time.RFC3339Nano,
+		}
 	} else {
 		logger.Formatter = &LogstashFormatter{TimestampFormat: time.RFC3339Nano}
 	}

helper_test.go

@@ -1,14 +1,17 @@
 package logging
 
 import (
+	"bytes"
 	"context"
+	"encoding/json"
 	"net/http"
 	"testing"
 	"time"
 
-	"github.com/snabble/go-logging/v2/tracex"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/snabble/go-logging/v2/tracex"
 )
 
 func Test_LifecycleStart_AcceptsNil(t *testing.T) {
@@ -34,3 +37,51 @@ func Test_Call_UsesTrace(t *testing.T) {
 	assert.Contains(t, capture.String(), "trace")
 	assert.Contains(t, capture.String(), "span")
 }
+
+func Test_SetGoogle(t *testing.T) {
+	require.NoError(t, SetGoogle("debug"))
+	defer SetWithConfig("info", &DefaultLogConfig) // Reset to default
+
+	tt := []struct {
+		level   string
+		message string
+		logFn   func()
+	}{
+		{
+			level:   "debug",
+			message: "__debug__",
+			logFn:   func() { Log.Debug("__debug__") },
+		},
+		{
+			level:   "info",
+			message: "__info__",
+			logFn:   func() { Log.Info("__info__") },
+		},
+		{
+			level:   "warning",
+			message: "__warn__",
+			logFn:   func() { Log.Warn("__warn__") },
+		},
+		{
+			level:   "error",
+			message: "__error__",
+			logFn:   func() { Log.Error("__error__") },
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.level, func(t *testing.T) {
+			b := bytes.NewBuffer(nil)
+			Log.Out = b
+
+			tc.logFn()
+
+			result := map[string]string{}
+			require.NoError(t, json.Unmarshal(b.Bytes(), &result))
+
+			assert.Equal(t, tc.message, result["message"])
+			assert.Equal(t, tc.level, result["severity"])
+			assert.NotEmpty(t, result["timestamp"])
+		})
+	}
+}