Please Take a Number

In the Internet world of seemingly endless computer resources, it’s not often that a website requires visitors to wait in line to visit, but a recent Dancing Mammoth project called for just that.

The Requirements:

  • Visitors will be added to a Virtual Waiting Room prior to advancing to website content.
  • Visitors will be advanced according to First In First Out.
  • Page must indicate current position in line via a client provided Flash object.
  • An administrator must be able to control flow of traffic.

The client expected light traffic to their video chat feature, so we decided that capturing queue data in a single table was the most efficient way to go. We could then poll at a some set interval to determine a visitor’s place in line, and take action based on the result.

The client-provided Flash object required use of a bit of javascript, so I decided to go ahead and implement the polling with the jQuery library’s ajax functionality — I ♥ jQuery. Here’s what the javascript function looks like:

function updatePosition()
		type: "GET", 
		url: "queue/index.php", 
		data: "sess=<?php echo $session_id ?>&random=" + new Date().getTime(), 
		dataType: "xml", 
		success: function(xml){
			var ky = "";
			var val = "";
			var action = "";
			var pos = 0;
			$("response", xml).each(function(){
				$("action", this).each(function(){
					action = $("key", this).text();
					val = $("value", this).text();
					if(action == "forward")
						// Forward
						pos = val;

If you’d like to review all the sample files, you can download them here, but no warranty is expressed or implied.

jQuery sends the visitor’s session id (as well as a random string — always send a random string when making ajax GET calls or IE will give you cached content) to a script that checks the queue and returns some XML with the action and associate value. Then the visitor is either forward to the content, or their position in line is displayed.

On the back end, the VirtualWaitingRoom class provides functionality to retrieve queue position, administratively advance visitors through the queue, and remove records for abandoned sessions.

The project was a success and while there’s nothing especially complex about it, this Virtual Waiting Room is a good short example of how various web technologies can come together to provide a unique solution.

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