Question

If one request will be take a long time for execution, another tabs will wait until first request will completed. Why? Please explain me. And how to solve it? Here my code:

var http = require("http");
var url = require("url");

http.createServer(function(request, response) {

    if (url.parse(request.url).pathname == '/long')
    {
        function longlong()
        {
            var counter = 0;
            var startTime = new Date().getTime();
            while (new Date().getTime() < startTime + 10000)
            {
                counter++;
            }
            return counter;
        }

        response.writeHead(200, {"Content-Type": "text/plain"});
        response.write(longlong() + '');
        response.end();
    }
    else
    {
      response.writeHead(200, {"Content-Type": "text/plain"});
      response.write(0 + '');
      response.end();
    }

}).listen(8888);

Answer 1

Good read:

http://blog.mixu.net/2011/02/01/understanding-the-node-js-event-loop/

A key line from that write up is:

…however, everything runs in parallel except your code

That means expensive I/O should be async but your code can block. but, it’s typically expensive I/O that we’re worried about blocking on the server.

See this other question for more details with an example: Node.js blocking the event loop?