Why aren't my JQuery .ajax requests being made in parallel?

Question

I am trying to make two ajax requests in parallel using jQuery like this:

    var sources = ["source1", "source2"];

    $(sources).each(function() {
      var source = this;
      $.ajax({
        async: true,
        type: "POST",
        data: {post: "data", in: "here"},
        url: "/my/url/" + source,
        success: function(data) {
          process_result(data);
        }
      });
    });

I got the basic structure from this question, but my requests still aren't being made in parallel. "source1" takes a while to complete, and I can see on the server that the second request isn't made until the first is completed.

As far as I can tell, I don't have any other active requests, so I don't think it's a problem with the maximum number of parallel requests for the browser. Am I missing something else here?

Answer 1

jQuery does not queue AJAX requests. If you're sure you're not making any other requests your end, how about the server? Maybe it only has one worker?

EDIT: And just to make sure, I tested it with a script that launches 2 AJAX POST requests to a PHP script which sleeps for 5 seconds. They were not queued.

Answer 2

are you using php? are you using session_start()? sessions cannot be opened in parallel by multiple requests, to they will wait one after another to finish what they're doing.