Want to win a PS4? Go Premium and enter to win our High-Tech Treats giveaway. Enter to Win


Memory leak with Ajax?

Posted on 2006-07-20
Medium Priority
Last Modified: 2011-09-20
I'm sorry for the overlap with ColdFusion but we have not been able to get any answers there....

We're using CFAJAX and javascript to update a page every X seconds with information.  As a test, we have a page that just updates itself with the time, being pulled via AJAX from another script.

Each time it runs, IE consumes more memory until it finally explodes....

We're doing an implementation of AJAX with a test script, based on the engine found at http://www.indiankey.com/cfajax/project.asp
and a modified version of the script from coldfusionjournal (Sept 2005, "What's Ajax, Part 1")

The code is simple - it triggers an AJAX request to a CF script that returns the current time.  For testing purposes, we set a javascript setTimeout
to loop every 50 milliseconds to update the date/time.  The problem is that each request increases the amount of RAM being used on
the desktop machine by IE until the machine grinds to a hault.

We are NOT concatonating the new value to an old value (ie. building a huge string).  Each request replaces the value.

Here's the script:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<script type="text/javascript">_cfscriptLocation="model.cfm";</script>
<script type="text/javascript" src="core/engine.js"></script>
<script type="text/javascript">
     function getGreetings()               {
     DWREngine._execute(_cfscriptLocation, null, 'getGreetings', getGreetings_result);
     function getGreetings_result(msg)      {
          immsg.innerHTML = msg;

<body onload="getGreetings();">
<div id="immsg" style="height:30px;"></div>


... and here is what it is calling:


<cfinclude template="core/cfajax.cfm">
<cffunction name="getGreetings" returntype="string">
     <cfreturn "The time is " & timeformat(now(),'h:MM:SS tt') & ", Greetings." />

Any suggestions?  In the real world we are not going to be checking time every 50 ms, but we may be checking items every 10-15 seconds and have one screen up for hours or more.

Is this a known issue with AJAX and IE?  The ColdFusion portions are all server side; the memory being consumed is client side.

Question by:drgdrg
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
LVL 15

Expert Comment

ID: 17148886
OK, first you have to eliminate IE's memory bug. How does it function in Firefox? If this works OK, it's the memory bug, if not, it's probably a real memory leak. I don't know how CF implements its Ajax calls, so it's hard to guess what it's doing under the covers. However, a potential bug is with the msg param. Try this small change:

 function getGreetings_result(msg)      {
          immsg.innerHTML = msg;
          msg = null;

Expert Comment

ID: 17148907
I'm not familiar with CF, but what is likely happenning is that a new request object is created each time getGreetings() is called.  I had a problem similar to this.

What would be easier on the RAM is creating 1 request object, then simply setting the .open() and then .send() each time the function is called.  I'm not sure if the library you are using can do that though.

<script type="text/javascript">
var req = new RequestObject() // changes depending on IE6, IE5- or FF/Opera/Safari
req.onreadystatechange = function() {
    if (this.readyState == 4 && (this.status == 200 || this.status == 304)) {  // 304 means OK, but pulled from cache
function getGreetings() {
function getGreetings_result(msg)      {
    immsg.innerHTML = msg;

I haven't tested this code, but it's basically what I think you need.

Author Comment

ID: 17214344
It seems to be a glitch in the Ajax engine - there are many out there.  We found a tag wddxAJAX which uses a different engine and it has no memory leak.  Don't be misled by the name - you don't have to do everything in wddx or xml....  But the tag works really well and seems to have no memory issues.

Thanks anyway

Accepted Solution

ee_ai_construct earned 0 total points
ID: 17259593
Closed, 500 points refunded.
Community Support Moderator
replacement part #xm34

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Having worked on larger scale sites, we found out that you are bound to look at more scalable solutions to integrating widgets, code snippets or complete applications and mesh them into functional sites, in any given composition. To share some of…
This article discusses the difference between strict equality operator and equality operator in JavaScript. The Need: Because JavaScript performs an implicit type conversion when performing comparisons, we have to take this into account when wri…
The viewer will learn the basics of jQuery, including how to invoke it on a web page. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery.: (CODE)
The viewer will learn the basics of jQuery including how to code hide show and toggles. Reference your jQuery libraries: (CODE) Include your new external js/jQuery file: (CODE) Write your first lines of code to setup your site for jQuery…

650 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question