关于golang:聊聊dubbogoproxy的AccessLogFilter

序

本文次要钻研一下 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 办法通过 extension.SetFilterFunc 注册了名为 constant.AccessLogFilter 的 context.FilterFunc，而后执行 accessLogWriter.Write()；accessLog 办法返回 context.FilterFunc，该 func 通过 buildAccessLogMsg 构建 accessLogMsg，而后执行 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 办法应用 strings.Builder 构建 accesslog，顺次打印 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 办法往 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 办法会按日期对 log 进行宰割，最初通过 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，而后往 AccessLogDataChan 写入 accessLogData；而后执行 accessLogWriter.Write() 启动协程遍历 AccessLogDataChan，执行 writeLogToFile。

doc

• dubbo-go-proxy