关于golang:聊聊zerolog的Formatter

序

本文次要钻研一下 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 办法针对不同的 field 来取不同的 Formatter，而后执行 Formatter 获取 string，最初通过 buf.WriteString(s) 写入；如果 FormatTimestamp 没有设置，则取 TimeFormat 创立 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")
}

输入

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

小结

zerolog 的 ConsoleWriter 定义了 Formatter 用于自定义输入格局，如果 FormatTimestamp 没有设置，则取 TimeFormat 创立 Formatter。

doc

• zerolog