The Azure Hosting Platform

The Azure web apps hosting technology is built on top of the fully managed PaaS environment. The PaaS environment (covered in the upcoming section, “Azure Cloud Services (PaaS)”) is a platform on which you can build applications without the overhead of managing the infrastructure on which they run. Azure web apps sit on top of this environment and allow you to leverage Azure cloud services in an easier way for building and hosting your web applications. This includes new applications as well as existing applications. (Even those with sticky sessions can be moved to this environment without changes.)

Azure web apps are run on a set of VMs shared as a resource pool in Azure (on your behalf). You don’t have control over these machines, nor do you want it. Instead, Azure takes care of all infrastructure concerns on your behalf (including automatic patching). Your app is isolated and hosted in VMs dedicated to your application. This ensures predictable performance and security isolation.

One of the biggest benefits of Azure hosting (outside of no infrastructure management) is scalability. You can easily scale your application platform to meet demand (and scale down when demand subsides). You do so from the Azure portal; it is as easy as moving a slider control. In fact, Azure has an AutoScale feature that allows you to increase the virtual instances (called nodes) running your application based on CPU consumption. If your application meets a target percentage of CPU consumption (you set the target), you can tell your app to run on additional nodes. Of course, AutoScale will also scale back down.