javascript - Node.js progress indicator feedback

Question

I have a question about the progress of sending with Node.js 'request'. I have a Node.js application that acts as a proxy, actually forwarding a body to another server. I want to see the progress of this upload action. Now I am doing this:

BROWSER 
   -> UPLOAD TO NODE 
   -> UPLOAD TO 3rd PARTY SERVICE 
   -> RETURN 3rd PARTY RESPONSE TO BROWSER

If this is possible, I would log it to check in the console.log how much progress is done. But, would it also be possible to return a

res.send(progress)

in the mean time, while waiting for the upload to finish and send the client back the upload has succeeded?

BROWSER 
   -> UPLOAD TO NODE
   -> UPLOAD TO 3rd PARTY SERVICE 
       -> RETURN progress <- 
       -> RETURN progress <- 
       ...etc.
   -> RETURN 3rd PARTY RESPONSE TO BROWSER

This is the upload code (pretty much straightforward).

var requestOptions = {
    timeout: 120000,
    url: url, //URL to hit
    method: 'post',
    headers: headers,
    body: payload //Set the body as a string
};


request(requestOptions, function (error, response, body) {
    if (error) {
        res.send(error);
    }
    else {
        //res.sendStatus(response.statusCode);
        console.log("[RETURNING RESPONSE BODY]");
        res.send(body);
    }
});

Answer 1

Your question contains two parts. One is for getting the progress from request, which can be found here: Upload Progress — Request

The other part would be notifying the browser of the progress. The HTTP protocol does not let you send multiple responses, so using res.send(progress) is not possible.

However, you can keep sending partial responses until it finishes. Writing something to res without closing it is as simple as res.write("string"), but accessing the response can be harder: Accessing partial response using AJAX or WebSockets?

You also need a way to wrap the body (and also errors) from the backing server so that it can fit as the final partial response.

Another solution would be opening another WebSocket request to track the uploading/downloading process. socket.io is a good library for node for this purpose.