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The goal of a Content Delivery Network (CDN)is to serve content from a server that is located geographically closer to yourusers. It’s a shorter distance to travel, and this means quicker responsetimes. A CDN essentially is a collection of server nodes located around theworld that contain a clone of static files.

The benefits of using a CDN extend far beyond just brilliantresponse times, using a CDN also reduces the amount of bandwidth and requeststhat are served from your website. You will still get all the benefits ofcaching, compression and a wider network for your website. Because your websitewill have static content served from such a wide network, it means that theload will be extremely well balanced across your users around the world. Say,for example, you were about to launch a new product online and expect highvolumes of traffic, this large distributed network of nodes is much betterequipped to handle instantaneous high load.

Suppose you’ve built an app called Surf Store, and you run itagainst the Yahoo! YSlow web performance tool. Imagine that the performancescore for the site currently comes in at 91 out of 100. This is a good score,but, unfortunately, you still score an 'F' for a Content Delivery Network. Ireckon you could do better! Figure 1 shows the result that the Yahoo! YSlowtool produces.

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Adding your website components to a CDN is an easy transition.However, depending on your development environment, it may not always be thatadvisable to work directly off a CDN while your website is still underdevelopment. You may have a development team that constantly needs to accessthese files and this can end up adding to your bandwidth bills. I often findthat it is best to work off local copies while in development and, then, switchto the CDN once the website is in production. I am going to show you atechnique in ASP.NET MVC that will allow you to easily work with a CDN whilestill in development.

ASP.NET MVC HTML Helperfor a CDN

We can easily add a HTML helper to our sample application thatcontains a switch between our development content and the production content ona CDN. Whether you work in a team or not, it can still be beneficial to usedevelopment content before moving to production content when your site goeslive. The key to using this technique is matching the local file structure tothat of your CDN. This makes it easier to navigate between folders and alsoallows us to easily map to certain files. Let’s run through an example thatmakes use of this technique.

Begin by adding a key to the Web.config file with the location ofthe CDN.

Listing 1 Adding the CDN URL to the Web.config

In listing 1, we simply add the URL of the Content DeliveryNetwork to the appSettingssection of the Web.config file. Next, we are going to use this CDN URL to buildup a path for our content depending on whether we are in release mode or debugmode. Begin by adding a new class file to the solution—I named it CdnUtils.Figure 2 shows the newly created class file in the Solution Explorer of thesample application.

Inside this new class, add the code in listing 2.

Listing 2 Using the URL of the CDN in debug/releasemode

The code in listing 2 uses the content path that is passed inand simply updates it with the URL of the CDN depending on whether or not thecode is in release mode. If we are still in debug mode, the code will run asnormal and simply return the content path that was passed in. Only if we are inrelease mode will the URL of the CDN get appended to the content path.

Finally, we need to update our views to use the new HTML helpermethod that we wrote. Instead of calling an HTML image tag like so:

Asp.net C Dev Or Prod 2

We now use:

And this will produce the following HTML when the web page isrendered:

This simple change ensures that, while you are still developinglocally, you aren’t using the bandwidth of your CDN and racking up a heftybill!

Summary

Every time you open up a webpage, you are often making a roundtrip to a server halfway around the world to retrieve the components requiredto load the page. These round trips take time and, not surprisingly, thefurther away that you are from the hosting server, the longer it will take youto download the components of a webpage. The ability to improve this delaycomes in the form of a Content Delivery Network. We implemented a technique inthe sample Surf Store application that allowed us to easily switch between thecontent on a CDN and the local content while in development. This techniquewill speed up your website and hopefully save you some money on your CDNbandwidth bills!

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Asp.net C Dev Or Prod Key