package logrus import ( "bytes" "encoding/json" "fmt" ) type fieldKey string // FieldMap allows customization of the key names for default fields. type FieldMap map[fieldKey]string // Default key names for the default fields const ( FieldKeyMsg = "msg" FieldKeyLevel = "level" FieldKeyTime = "time" ) func (f FieldMap) resolve(key fieldKey) string { if k, ok := f[key]; ok { return k } return string(key) } // JSONFormatter formats logs into parsable json type JSONFormatter struct { // TimestampFormat sets the format used for marshaling timestamps. TimestampFormat string // DisableTimestamp allows disabling automatic timestamps in output DisableTimestamp bool // DataKey allows users to put all the log entry parameters into a nested dictionary at a given key. DataKey string // FieldMap allows users to customize the names of keys for default fields. // As an example: // formatter := &JSONFormatter{ // FieldMap: FieldMap{ // FieldKeyTime: "@timestamp", // FieldKeyLevel: "@level", // FieldKeyMsg: "@message", // }, // } FieldMap FieldMap } // Format renders a single log entry func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) { data := make(Fields, len(entry.Data)+3) 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 } } if f.DataKey != "" { newData := make(Fields, 4) newData[f.DataKey] = data data = newData } prefixFieldClashes(data, f.FieldMap) timestampFormat := f.TimestampFormat if timestampFormat == "" { timestampFormat = defaultTimestampFormat } if !f.DisableTimestamp { data[f.FieldMap.resolve(FieldKeyTime)] = entry.Time.Format(timestampFormat) } data[f.FieldMap.resolve(FieldKeyMsg)] = entry.Message data[f.FieldMap.resolve(FieldKeyLevel)] = entry.Level.String() var b *bytes.Buffer if entry.Buffer != nil { b = entry.Buffer } else { b = &bytes.Buffer{} } err := json.NewEncoder(b).Encode(data) if err != nil { return nil, fmt.Errorf("Failed to marshal fields to JSON, %v", err) } return b.Bytes(), nil }