聊聊zerolog的Formatter

序

本文主要研究一下zerolog的Formatter

Formatter

github.com/rs/zerolog@v1.20.0/console.go

// Formatter transforms the input into a formatted string.
type Formatter func(interface{}) string

Formatter接口定义了一个func用于将interface{}转换为string

ConsoleWriter

github.com/rs/zerolog@v1.20.0/console.go

type ConsoleWriter struct {
 // Out is the output destination.
 Out io.Writer
 // NoColor disables the colorized output.
 NoColor bool
 // TimeFormat specifies the format for timestamp in output.
 TimeFormat string
 // PartsOrder defines the order of parts in output.
 PartsOrder []string
 FormatTimestamp Formatter
 FormatLevel Formatter
 FormatCaller Formatter
 FormatMessage Formatter
 FormatFieldName Formatter
 FormatFieldValue Formatter
 FormatErrFieldName Formatter
 FormatErrFieldValue Formatter
}

ConsoleWriter定义了TimeFormat、FormatTimestamp、FormatLevel、FormatCaller、FormatMessage、FormatFieldName、FormatFieldValue、FormatErrFieldName、FormatErrFieldValue属性

writePart

github.com/rs/zerolog@v1.20.0/console.go

// writePart appends a formatted part to buf.
func (w ConsoleWriter) writePart(buf *bytes.Buffer, evt map[string]interface{}, p string) {
 var f Formatter
 switch p {
 case LevelFieldName:
 if w.FormatLevel == nil {
 f = consoleDefaultFormatLevel(w.NoColor)
 } else {
 f = w.FormatLevel
 }
 case TimestampFieldName:
 if w.FormatTimestamp == nil {
 f = consoleDefaultFormatTimestamp(w.TimeFormat, w.NoColor)
 } else {
 f = w.FormatTimestamp
 }
 case MessageFieldName:
 if w.FormatMessage == nil {
 f = consoleDefaultFormatMessage
 } else {
 f = w.FormatMessage
 }
 case CallerFieldName:
 if w.FormatCaller == nil {
 f = consoleDefaultFormatCaller(w.NoColor)
 } else {
 f = w.FormatCaller
 }
 default:
 if w.FormatFieldValue == nil {
 f = consoleDefaultFormatFieldValue
 } else {
 f = w.FormatFieldValue
 }
 }
 var s = f(evt[p])
 if len(s) > 0 {
 buf.WriteString(s)
 if p != w.PartsOrder[len(w.PartsOrder)-1] { // Skip space for last part
 buf.WriteByte(' ')
 }
 }
}

writePart方法针对不同的field来取不同的Formatter,然后执行Formatter获取string,最后通过buf.WriteString(s)写入;如果FormatTimestamp没有设置,则取TimeFormat创建Formatter

实例

func formatDemo() {
 output := zerolog.ConsoleWriter{Out: os.Stdout, TimeFormat: time.RFC3339}
 output.FormatLevel = func(i interface{}) string {
 return strings.ToUpper(fmt.Sprintf("| %-6s|", i))
 }
 output.FormatMessage = func(i interface{}) string {
 return fmt.Sprintf("***%s****", i)
 }
 output.FormatFieldName = func(i interface{}) string {
 return fmt.Sprintf("%s:", i)
 }
 output.FormatFieldValue = func(i interface{}) string {
 return strings.ToUpper(fmt.Sprintf("%s", i))
 }
 log := zerolog.New(output).With().Timestamp().Logger()
 log.Info().Str("foo", "bar").Msg("Hello World")
}

输出

2021年01月06日T23:16:42+08:00 | INFO | ***Hello World**** foo:BAR

小结

zerolog的ConsoleWriter定义了Formatter用于自定义输出格式,如果FormatTimestamp没有设置,则取TimeFormat创建Formatter。

doc

• zerolog

本文来自:Segmentfault

感谢作者:.container .card .information strong

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