Cloud Application Architectures

Web Application Design

I cannot possibly address the intricacies of each of the many platforms developers use in building web applications, but most of the issues you will face have nothing to do with your underlying choice of platform. Whether written in .NET, Ruby, Java, PHP, or anything else, web applications share a similar general architecture—and architecture makes or breaks an application in the cloud.

Figure 4-1 illustrates the generic application architecture that web applications share.

Figure 4-1. Most web applications share the same basic architecture

You may move around or combine the boxes a bit, but you are certain to have some kind of (most often scripting) language that generates content from a combination of templates and data pulled from a model backed by a database. The system updates the model through actions that execute transactions against the model.

System State and Protecting Transactions

The defining issue in moving to the cloud is how your application manages its state. Let’s look at the problem of booking a room in a hotel.

The architecture from Figure 4-1 suggests that you have represented the room and the hotel in a model. For the purposes of this discussion, it does not matter whether you have a tight separation between model, view, and data, or have mixed them to some degree. The key point is that there is some representation of the hotel and room data in ...