gistfile1.js

/* Jquery plugin for quick Comet long polling connections
Nothing special about this (just a recursive Ajax call). 
The key is having the server hold connections open until there's data to push back to the client.
This can be done with Nginx and the nginx_http_push_module (http://github.com/slact/nginx_http_push_module)
---------------------------------------------------------------------------*/
(function($){
  var changed, etag;
  var wait = 1000;
  
  $.comet = function(url, success_callback, error_callback) {
    $.ajax({
      type: "GET",
      dataType: "script",
      url: url,
      cache: true,
      beforeSend: function(oXhr) { 
   		  oXhr.setRequestHeader('If-Modified-Since', changed); 
   		  oXhr.setRequestHeader('If-None-Match', etag); 
   		},
      success: function(data, a, b, c){
        if(success_callback) success_callback(data);
      },
      error: function(a,b,c){
        if(error_callback) error_callback(a,b,c);
      },      
      complete: function (oXhr, textStatus) {
        if(textStatus == "success"){
          etag = oXhr.getResponseHeader('Etag');
          changed = oXhr.getResponseHeader('Last-Modified');
          $.comet(url, success_callback, error_callback);
        } else {
          wait = wait * 1.5;
          setTimeout(function(){
            $.comet(url, success_callback, error_callback);
          }, wait);
        }
      }
    });
  };
})(jQuery);
/*
Usage
------------------------------------------------------*/
$.comet(function(data){
  $('#content').prepend(data.someAttribute)
});