序

本文主要研究一下dubbo-go-proxy的AccessLogFilter

AccessLogFilter

dubbo-go-proxy/pkg/filter/accesslog/access_log.go

var accessLogWriter = &model.AccessLogWriter{AccessLogDataChan: make(chan model.AccessLogData, constant.LogDataBuffer)}

func init() {
    extension.SetFilterFunc(constant.AccessLogFilter, accessLog())
    accessLogWriter.Write()
}

// access log filter
func accessLog() context.FilterFunc {
    return func(c context.Context) {
        alc := config.GetBootstrap().StaticResources.AccessLogConfig
        if !alc.Enable {
            return
        }
        start := time.Now()
        c.Next()
        latency := time.Now().Sub(start)
        // build access_log message
        accessLogMsg := buildAccessLogMsg(c, latency)
        if len(accessLogMsg) > 0 {
            accessLogWriter.Writer(model.AccessLogData{AccessLogConfig: alc, AccessLogMsg: accessLogMsg})
        }
    }
}

init方法通过extension.SetFilterFunc注册了名为constant.AccessLogFilter的context.FilterFunc，然后执行accessLogWriter.Write()；accessLog方法返回context.FilterFunc，该func通过buildAccessLogMsg构建accessLogMsg，然后执行accessLogWriter.Writer

buildAccessLogMsg

dubbo-go-proxy/pkg/filter/accesslog/access_log.go

func buildAccessLogMsg(c context.Context, cost time.Duration) string {
    req := c.(*http.HttpContext).Request
    valueStr := req.URL.Query().Encode()
    if len(valueStr) != 0 {
        valueStr = strings.ReplaceAll(valueStr, "&", ",")
    }

    builder := strings.Builder{}
    builder.WriteString("[")
    builder.WriteString(time.Now().Format(constant.MessageDateLayout))
    builder.WriteString("] ")
    builder.WriteString(req.RemoteAddr)
    builder.WriteString(" -> ")
    builder.WriteString(req.Host)
    builder.WriteString(" - ")
    if len(valueStr) > 0 {
        builder.WriteString("request params: [")
        builder.WriteString(valueStr)
        builder.WriteString("] ")
    }
    builder.WriteString("cost time [ ")
    builder.WriteString(strconv.Itoa(int(cost)) + " ]")
    err := c.(*http.HttpContext).Err
    if err != nil {
        builder.WriteString(fmt.Sprintf("invoke err [ %v", err))
        builder.WriteString("] ")
    }
    resp := c.(*http.HttpContext).TargetResp.Data
    rbs, err := getBytes(resp)
    if err != nil {
        builder.WriteString(fmt.Sprintf(" response can not convert to string"))
        builder.WriteString("] ")
    } else {
        builder.WriteString(fmt.Sprintf(" response [ %+v", string(rbs)))
        builder.WriteString("] ")
    }
    //builder.WriteString("\n")
    return builder.String()
}

buildAccessLogMsg方法使用strings.Builder构建accesslog，依次打印time、remoteAddr、host、request params、cost time、err、resp

AccessLogWriter

dubbo-go-proxy/pkg/model/log.go

// access log chan
type AccessLogWriter struct {
    AccessLogDataChan chan AccessLogData
}

// access log data
type AccessLogData struct {
    AccessLogMsg    string
    AccessLogConfig AccessLogConfig
}

// writer msg into chan
func (alw *AccessLogWriter) Writer(accessLogData AccessLogData) {
    select {
    case alw.AccessLogDataChan <- accessLogData:
        return
    default:
        logger.Warn("the channel is full and the access logIntoChannel data will be dropped")
        return
    }
}

AccessLogWriter定义了AccessLogDataChan属性，它是一个AccessLogData类型的channel；Writer方法往AccessLogDataChan写入accessLogData

Write

dubbo-go-proxy/pkg/model/log.go

// write log into out put path
func (alw *AccessLogWriter) Write() {
    go func() {
        for accessLogData := range alw.AccessLogDataChan {
            alw.writeLogToFile(accessLogData)
        }
    }()
}

// write log to file or console
func (alw *AccessLogWriter) writeLogToFile(ald AccessLogData) {
    alc := ald.AccessLogConfig
    alm := ald.AccessLogMsg
    if len(alc.OutPutPath) == 0 || alc.OutPutPath == constant.Console {
        logger.Info(alm)
        return
    }
    _ = WriteToFile(alm, alc.OutPutPath)
}

Write启动异步线程遍历AccessLogDataChan，执行writeLogToFile

WriteToFile

dubbo-go-proxy/pkg/model/log.go

// write message to access log file
func WriteToFile(accessLogMsg string, filePath string) error {
    pd := filepath.Dir(filePath)
    if _, err := os.Stat(pd); err != nil {
        if os.IsExist(err) {
            logger.Warnf("can not open log dir: %s, %v", filePath, err)
        }
        err = os.MkdirAll(pd, os.ModePerm)
        if err != nil {
            logger.Warnf("can not create log dir: %s, %v", filePath, err)
            return err
        }
    }
    logFile, err := os.OpenFile(filePath, os.O_CREATE|os.O_APPEND|os.O_RDWR, constant.LogFileMode)
    if err != nil {
        logger.Warnf("can not open the access log file: %s, %v", filePath, err)
        return err
    }
    now := time.Now().Format(constant.FileDateFormat)
    fileInfo, err := logFile.Stat()
    if err != nil {
        logger.Warnf("can not get the info of access log file: %s, %v", filePath, err)
        return err
    }
    last := fileInfo.ModTime().Format(constant.FileDateFormat)

    // this is confused.
    // for example, if the last = '2020-03-04'
    // and today is '2020-03-05'
    // we will create one new file to log access data
    // By this way, we can split the access log based on days.
    if now != last {
        err = os.Rename(fileInfo.Name(), fileInfo.Name()+"."+now)
        if err != nil {
            logger.Warnf("can not rename access log file: %s, %v", fileInfo.Name(), err)
            return err
        }
        logFile, err = os.OpenFile(fileInfo.Name(), os.O_CREATE|os.O_APPEND|os.O_RDWR, constant.LogFileMode)
        if err != nil {
            logger.Warnf("can not open access log file: %s, %v", fileInfo.Name(), err)
            return err
        }
    }
    _, err = logFile.WriteString(accessLogMsg + "\n")
    if err != nil {
        logger.Warnf("can not write to access log file: %s, v%", fileInfo.Name(), err)
        return err
    }
    return nil
}

WriteToFile方法会按日期对log进行分割，最后通过logFile.WriteString写入日志

小结

dubbo-go-proxy的AccessLogFilter通过extension.SetFilterFunc注册了名为constant.AccessLogFilter的context.FilterFunc，该func通过buildAccessLogMsg构建accessLogMsg，然后往AccessLogDataChan写入accessLogData；然后执行accessLogWriter.Write()启动协程遍历AccessLogDataChan，执行writeLogToFile。

doc

• dubbo-go-proxy