On flow delivery between microservices

As the title says , Recently, the landlord encountered a scene problem , Initially, I wanted to transfer flows between microservices , Results found , In the process of transmission , Stream will be lost , That is, the flow cannot be transferred in the ordinary way , Is there any alternative way or method to solve the problem

1 Scene question

In everyday projects , There are often imports and exports Excel The function of . In a requirement function , The design of the function is : Front end upload Excel Go backstage , Background analysis Excel, And upload the file to the ECS , And return the file fileId. Click the submit button on the page , The background will be based on the file fileId Download the file stream from the ECS .

In the initial design , Because the back-end micro services are divided into different services according to different functions , Therefore, it is a separate micro service that operates cloud service data , Ordinary business microservice modules only pass feign Etc , So the use of feign Interface call mode

feign Interface call Is to directly treat the file stream as a normal parameter in feign Interface , feign There is a problem with the way of calling , That is, the queried stream , Cannot return to business service .

2 Solution

Inquire relevant information , It is found that the flow cannot pass directly feign Interface call , Because the stream is in the transmission process , Cannot convert effectively , Therefore, all acceptance streams are empty . For this problem , There are two ways , The first is to replace the stream loading with byte array transmission , Byte array in feign Interface calling , Can effectively transmit ; The second way is through response Object delivery flow ; The third kind of , Listen to the big guy , feign If the interface call needs to pass the flow , Additional configuration is required , Add related transformations . ( Unknown , To be verified )

1 Through byte array

Cloud service interface

    @PostMapping("/upload")
    @ResponseBody
    public byte[] upload() throws IOException {
    

        //  Simulate getting file streams from cloud services 
        InputStream is = new ZipInputStream(null);

        byte[] buffer = new byte[1024];
        int len = 0;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while ((len = is.read(buffer)) != -1) {
    
            bos.write(buffer,0,len);
        }
        bos.flush();
        return bos.toByteArray();
    }

feign Interface

    @PostMapping("/upload")
    @ResponseBody
    byte[] upload();

Business services

    byte[] bytes = ossClient.upload();
	InputStream is = new ByteArrayInputputStream(bytes);

2 adopt Response

    @PostMapping("/upload")
    @ResponseBody
    public void upload(HttpServletResponse resp) throws IOException {
    

        //  Simulate getting file streams from cloud services 
        InputStream is = new ZipInputStream(null)
              
        OutputStream os = response.getOutputStream();
        byte[] bytes = new byte[1024];
        int len = 0;
        while ((len = is.read(bytes)) != -1) {
    
            os.write(bytes, 0, len);
        }
        is.close();
        os.flush();
        os.close();
   
    }

feign Interface

    @PostMapping("/upload")
    @ResponseBody
    feign.Response upload(HttpServletResponse resp);

Business services

    Response response = ossClient.upload();
	InputStream is = response.body().asInputStream();

3 summary

Through the above methods, we can know , All of them transfer streams through transformation , There is no way to transfer the flow directly , For mode three , We also need to learn and explore , Also welcome scholars who understand to add and correct .