Add human-readbale log output (#681)

Add human-readable log output. It prints out the exact source code line information.

formatter/formatter.go

@@ -0,0 +1,51 @@
+package formatter
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// TextFormatter formats logs into text with included source code's path
+type TextFormatter struct {
+	TimestampFormat string
+	LevelDesc       []string
+}
+
+// NewTextFormatter create new MyTextFormatter instance
+func NewTextFormatter() *TextFormatter {
+	return &TextFormatter{
+		LevelDesc:       []string{"PANC", "FATL", "ERRO", "WARN", "INFO", "DEBG", "TRAC"},
+		TimestampFormat: time.RFC3339, // or RFC3339
+	}
+}
+
+// Format renders a single log entry
+func (f *TextFormatter) Format(entry *logrus.Entry) ([]byte, error) {
+	var fields string
+	keys := make([]string, 0, len(entry.Data))
+	for k, v := range entry.Data {
+		if k == "source" {
+			continue
+		}
+		keys = append(keys, fmt.Sprintf("%s: %v", k, v))
+	}
+
+	if len(keys) > 0 {
+		fields = fmt.Sprintf("[%s] ", strings.Join(keys, ", "))
+	}
+
+	level := f.parseLevel(entry.Level)
+
+	return []byte(fmt.Sprintf("%s %s %s%s: %s\n", entry.Time.Format(f.TimestampFormat), level, fields, entry.Data["source"], entry.Message)), nil
+}
+
+func (f *TextFormatter) parseLevel(level logrus.Level) string {
+	if len(f.LevelDesc) < int(level) {
+		return ""
+	}
+
+	return f.LevelDesc[level]
+}