Can a Node.js http request wait for a signal from another http request in order to be finished?

Question

I'm trying to find a way to do what is shown in the diagram below with Node.js. Is it even possible?

Basically, I need to put an http request to wait for a signal from another http request in order to finish.

Answer 1

According to this you can provide a callback to an http request which you could use to finish the request to your server.

Answer 2

My two cents; try the following code, although it's not properly structured it should do the trick. You can call /first in different tabs multiple times and refresh /second to see them responding one by one.

var http = require('http'),
    Promise = require('promise');
var queue = [];

function handleRequest(request, response) {
    switch (request.url) {
    case "/first":
        new Promise(function (resolve) {
            var guid = 'some-guid';
            // enqueue in redis or whatever you like and save the guid to match later.
            queue.push({
                data: guid,
                resolve: resolve
            });
        }).then(function () {
            response.end('1st finished');
        });
        break;
    case "/second":
        // queue consumer calls this (probably with the guid parameter)
        queue.length && queue.some(function (item) {
            if (item.data === 'some-guid') {
                item.resolve();
            }
        });
        response.end();
        break;
    default:
        response.end('call /first, then /second');
        break;
    }
}
var server = http.createServer(handleRequest);
server.listen(8080, function () {
    console.log("Server listening on: http://localhost:%s", 8080);
});