聊聊zerolog的send

序

本文主要研究一下zerolog的send

实例

func sendDemo() {
    zerolog.TimeFieldFormat = zerolog.TimeFormatUnix

    log.Info().
        Str("Name", "Tom").
        Send()

    log.Info().
        Str("Name", "Tom").
        Msg("hello world")
}

使用Send或者Msg来发送log

输出

{"level":"info","Name":"Tom","time":1609509525}
{"level":"info","Name":"Tom","time":1609509525,"message":"hello world"}

Send

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

// Send is equivalent to calling Msg("").
//
// NOTICE: once this method is called, the *Event should be disposed.
func (e *Event) Send() {
    if e == nil {
        return
    }
    e.msg("")
}

Send方法相当于Msg("")

msg

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

func (e *Event) msg(msg string) {
    for _, hook := range e.ch {
        hook.Run(e, e.level, msg)
    }
    if msg != "" {
        e.buf = enc.AppendString(enc.AppendKey(e.buf, MessageFieldName), msg)
    }
    if e.done != nil {
        defer e.done(msg)
    }
    if err := e.write(); err != nil {
        if ErrorHandler != nil {
            ErrorHandler(err)
        } else {
            fmt.Fprintf(os.Stderr, "zerolog: could not write event: %v\n", err)
        }
    }
}

msg方法先执行hook，之后对于有msg的添加message字段，如果done不为nil则defer注册回调，之后执行e.write()

write

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

func (e *Event) write() (err error) {
    if e == nil {
        return nil
    }
    if e.level != Disabled {
        e.buf = enc.AppendEndMarker(e.buf)
        e.buf = enc.AppendLineBreak(e.buf)
        if e.w != nil {
            _, err = e.w.WriteLevel(e.level, e.buf)
        }
    }
    putEvent(e)
    return
}

write在level不为Disabled的时候会追加endMarker及lineBreaker；对于e.w不为nil时，执行e.w.WriteLevel(e.level, e.buf)进行输出；之后执行putEvent归还event

putEvent

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

func putEvent(e *Event) {
    // Proper usage of a sync.Pool requires each entry to have approximately
    // the same memory cost. To obtain this property when the stored type
    // contains a variably-sized buffer, we add a hard limit on the maximum buffer
    // to place back in the pool.
    //
    // See https://golang.org/issue/23199
    const maxSize = 1 << 16 // 64KiB
    if cap(e.buf) > maxSize {
        return
    }
    eventPool.Put(e)
}

putEvent方法先判断e.buf的大小是否超过maxSize，超过则直接返回，否则执行eventPool.Put(e)将event归还到eventPool中

Info

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

// Info starts a new message with info level.
//
// You must call Msg on the returned event in order to send the event.
func (l *Logger) Info() *Event {
    return l.newEvent(InfoLevel, nil)
}

Info方法执行的l.newEvent(InfoLevel, nil)

newEvent

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

func (l *Logger) newEvent(level Level, done func(string)) *Event {
    enabled := l.should(level)
    if !enabled {
        return nil
    }
    e := newEvent(l.w, level)
    e.done = done
    e.ch = l.hooks
    if level != NoLevel {
        e.Str(LevelFieldName, LevelFieldMarshalFunc(level))
    }
    if l.context != nil && len(l.context) > 1 {
        e.buf = enc.AppendObjectData(e.buf, l.context)
    }
    return e
}

func newEvent(w LevelWriter, level Level) *Event {
    e := eventPool.Get().(*Event)
    e.buf = e.buf[:0]
    e.ch = nil
    e.buf = enc.AppendBeginMarker(e.buf)
    e.w = w
    e.level = level
    e.stack = false
    return e
}

newEvent方法从eventPool获取Event，然后设置done、hooks等属性

小结

zerolog的Send方法相当于Msg("")；newEvent方法从eventPool获取Event，然后设置done、hooks等属性；write在level不为Disabled的时候会追加endMarker及lineBreaker；对于e.w不为nil时，执行e.w.WriteLevel(e.level, e.buf)进行输出；之后执行putEvent归还event；

doc

• zerolog

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