如果刷新/重新打开页面，Django POST响应将引发异常

Question

I'm using Django in order to create a server which will download and track the progress of files. It has an input field for the url of the download link, and once I click on Download , it executes the following javascript code:

index.html

function startDownload() {
    var xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            completedFile = xhttp.responseText;
            document.getElementById(completedFile + "ProgBar").style.width = "100%";
            document.getElementById(completedFile + "ProgBar").innerHTML = "Completed!";
            setTimeout(delProgBar, 5000, completedFile);
        }
    };
    xhttp.open("POST", "http://localhost:8000/download/start/", true);
    xhttp.setRequestHeader("X-CSRFToken", '{{ csrf_token }}');
    xhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
    var downloadLink = document.getElementById("downloadInput").value;
    var sendString = "url=" + downloadLink;
    var downloadArray = downloadLink.split('/');
    var downloadName = downloadArray[downloadArray.length-1];
    addProgBar(downloadName, "0");
    xhttp.send(sendString);
}

Django views.py

def start(request):
    aux = request.POST['url']
    file_name = start_download(aux)
    print("###########")
    print(file_name)
    return HttpResponse(file_name)

This works completely fine IF I don't reload the page after starting the download. The POST Request is only being logged on Django Command Prompt window after it is completed (readyState check).

However, the page should show the download progress for other people that open the page after the download started. This however is throwing a big error on Django, with something like 4 Exceptions. I can post it later if necessary, but the main one seems to be:
ConnectionAbortedError: [WinError 10053] An established connection was aborted by the software in your host machine

I believe that what I'm doing wrong is trying to send a response to a client that did not generated the request.
Is there a way to receive the POST Response even if the client did not sent the original Request? Or is there another way to do what I'm trying to?

Thanks a lot!

Additional Info:
Tried with GET instead of POST and the same issue happens.

I believe that the main issue here is that the POST Request is only returning an answer to the client once the operation "start_download" finishes, which can take a while. I should instead send a response with "success" or "fail" to start the download and use GET Request to perform polling and get the download status.

Answer 1

Firstly it looks like the code checks for POST values. To fix this check if the request method is POST or GET. If its GET then you need to render to a page that displays the progress of the files.