聊聊rocketmq-client-go的TraceInterceptor

// WithTrace support rocketmq trace: https://github.com/apache/rocketmq/wiki/RIP-6-Message-Trace.
func WithTrace(traceCfg *primitive.TraceConfig) Option {
    return func(options *producerOptions) {
​
        ori := options.Interceptors
        options.Interceptors = make([]primitive.Interceptor, 0)
        options.Interceptors = append(options.Interceptors, newTraceInterceptor(traceCfg))
        options.Interceptors = append(options.Interceptors, ori...)
    }
}

func newTraceInterceptor(traceCfg *primitive.TraceConfig) primitive.Interceptor {
    dispatcher := internal.NewTraceDispatcher(traceCfg)
    dispatcher.Start()
​
    return func(ctx context.Context, req, reply interface{}, next primitive.Invoker) error {
        beginT := time.Now()
        err := next(ctx, req, reply)
​
        producerCtx := primitive.GetProducerCtx(ctx)
        if producerCtx.Message.Topic == dispatcher.GetTraceTopicName() {
            return next(ctx, req, reply)
        }
​
        // SendOneway && SendAsync has no reply.
        if reply == nil {
            return err
        }
​
        result := reply.(*primitive.SendResult)
        if result.RegionID == "" || !result.TraceOn {
            return err
        }
​
        sendSuccess := result.Status == primitive.SendOK
        costT := time.Since(beginT).Nanoseconds() / int64(time.Millisecond)
        storeT := beginT.UnixNano()/int64(time.Millisecond) + costT/2
​
        traceBean := internal.TraceBean{
            Topic:       producerCtx.Message.Topic,
            Tags:        producerCtx.Message.GetTags(),
            Keys:        producerCtx.Message.GetKeys(),
            StoreHost:   producerCtx.BrokerAddr,
            ClientHost:  utils.LocalIP,
            BodyLength:  len(producerCtx.Message.Body),
            MsgType:     producerCtx.MsgType,
            MsgId:       result.MsgID,
            OffsetMsgId: result.OffsetMsgID,
            StoreTime:   storeT,
        }
​
        traceCtx := internal.TraceContext{
            RequestId: primitive.CreateUniqID(), // set id
            TimeStamp: time.Now().UnixNano() / int64(time.Millisecond),
​
            TraceType:  internal.Pub,
            GroupName:  producerCtx.ProducerGroup,
            RegionId:   result.RegionID,
            TraceBeans: []internal.TraceBean{traceBean},
            CostTime:   costT,
            IsSuccess:  sendSuccess,
        }
        dispatcher.Append(traceCtx)
        return err
    }
}