package logrus import ( "encoding/json" "fmt" ) type fieldKey string type FieldMap map[fieldKey]string const ( FieldKeyMsg = "msg" FieldKeyLevel = "level" FieldKeyTime = "time" FieldKeyCaller = "method" ) func (f FieldMap) resolve(key fieldKey) string { if k, ok := f[key]; ok { return k } return string(key) } type JSONFormatter struct { // TimestampFormat sets the format used for marshaling timestamps. TimestampFormat string // FieldMap allows users to customize the names of keys for various fields. // As an example: // formatter := &JSONFormatter{ // FieldMap: FieldMap{ // FieldKeyTime: "@timestamp", // FieldKeyLevel: "@level", // FieldKeyMsg: "@message", // FieldKeyCaller: "@caller", // }, // } FieldMap FieldMap } func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) { data := make(Fields, len(entry.Data)+4) for k, v := range entry.Data { switch v := v.(type) { case error: // Otherwise errors are ignored by `encoding/json` // https://github.com/Sirupsen/logrus/issues/137 data[k] = v.Error() default: data[k] = v } } prefixFieldClashes(data) timestampFormat := f.TimestampFormat if timestampFormat == "" { timestampFormat = DefaultTimestampFormat } data[f.FieldMap.resolve(FieldKeyTime)] = entry.Time.Format(timestampFormat) data[f.FieldMap.resolve(FieldKeyMsg)] = entry.Message data[f.FieldMap.resolve(FieldKeyLevel)] = entry.Level.String() if ReportCaller() { data[f.FieldMap.resolve(FieldKeyCaller)] = entry.Caller } serialized, err := json.Marshal(data) if err != nil { return nil, fmt.Errorf("Failed to marshal fields to JSON, %v", err) } return append(serialized, '\n'), nil }