DiskCache plugin strategy for e-mail images with tracking

Question

Currently we're sending thousands of e-mails every day to our customers. An e-mail contains an image url with a specific Message ID. When the user downloads that image, I mark that message as opened in the database. For example:

http://cdn.mydomain.com/companylogos/{guid}.png?h=100&w=100&messageid=123

At this moment, every image request requires me to get the byte[ ] of the image from cache. Resize it. And Return it. This all takes place in a httphandler.

I would like to take the advantage of ImageResizer.net and the Disk Cache plugin. However, I still need to get the MessageId-querystring parameter. So I'm thinking about this solution.

Extending HttpModule

public class CustomInterceptModule : InterceptModule
{
    protected override void HandleRequest(HttpContext context, HttpModuleRequestAssistant ra, IVirtualFile vf)
    {
        var messageIdParam = context.Request.QueryString["messageId"];
        int messageId;

        if (!string.IsNullOrWhiteSpace(messageIdParam) && int.TryParse(messageIdParam, out messageId))
        {
            // Do something with the ID here   
        }

        base.HandleRequest(context, ra, vf);
    }
}

Does this method still creates high performance, disk cached, results? Or am I interrupting this because I'm extending the HttpModule and I'm adding my own logic in there.

Answer 1

If your goal is to increase performance and/or reduce the work you server needs to do, I would suggest that you should not use a full-size image for tracking purposes, but instead use an invisible 1x1.png image to track whether or not a message was opened, and simply use a standard img url that everybody shares (that can be distributed on a CDN and/or cached) for the image that people actually see.