Thumbnail Requests: Is it possible to request image directly

Thanks for responding Alfonso. I appreciate your time.

You're correct, I was being silly and made a mistake in my post. All of the thumbnail requests would still go into the browser request queue for that hostname and would be handled by the server.

However, the direct requests would be handled strictly by the web server and not by the app server (coldfusion in my case), which is my main goal. At any given time, our Coldfusion servers have plenty of other requests to serve and I would prefer not to add requests for previously generated thumbnails to their processing queues.

Instead of having each thumbnail request check if the thumbnail is available and up-to-date, I'm suggesting putting all of the file system checking into the initial request that returns the XML file listing. The server side connector script would then only need to be called for those images that are not up to date.

Now, let's switch topics back to the browser request queue stuff .....

When I suggested changes to the XML format in my original post, I started to put a CurrentFolder attribute that would hold a comma delimited list of thumbnailurl hostnames (or a set of XML children to hold the same info) for the directly requested thumbnails. The front end JS could then spread the direct request over those hostnames and be able to load more than 2 at a time (without browser addons or changing your FF config). Since they would be direct image requests, there would be less of a concern about making sure that session cookies, etc are sent with the request.

Of course, there are downsides such as the likelihood of having multiple versions of the same thumbnail image in browser cache because different hostnames were used to call it on successive loads of the folder. Anyway, I left that stuff out of my earlier post since that is not my main concern. It would be like icing on the cake. Plus since FF3 and IE8 are increasing the connection limit per hostname, the benefits of such tricks may be outweighed by the detriments.

Yes, I believe that it would reduce server load, especially for folders with lots of images ... but it probably should be tested.

As you probably know, Coldfusion MX7 is set to handle a certain number of simultaneous requests (usually like 6-8 per processor -- but don't quote me) and if that limit is reached other requests queue up and wait their turn. I believe other some other server-side platforms operate in a similar manner. By making direct calls for thumbnail images, those request would completely bypass the server-side processing queue ... which would be a good thing to me.

Now, on to your point about assigning users to a single hostname ...

In order to get around the browser's connection limit per hostname, thumbnail requests for each user would have to come from multiple hostnames. For example, if the user's browser was limited to 2 connections per hostname (like the vast majority of users), they would only be able to load two thumbnails at a time if all of image requests were sent to a single hostname. But if we were spreading requests for that user across 4 hostnames, then the user would be able to request 8 thumbnails at a time.

You can get around the caching problem by figuring out a way to consistently assign the same hostname to a particular image for every request. If the hostnames were loaded into an array, you could do something like (length of the thumbnail filename) mod (length of array) and then use the result of that as the array position for the selected hostname for that image. Such a method could consistenly return the same hostname for each image. Of course, the set of images would probably not be equally spread across the hostnames, but it would still give you the benefit of having multiple queues.

Alfonso,

I agree, the idea of spreading the static content request across multiple hostnames is more complex and probably not nearly as important.

That being said, where do we go from here? Is there something that I can do to help turn the idea of directly requesting static thumbnails into reality?