This is a continuation of an article that describes operational considerations for hosting solutions on Azure public cloud.   

There are several references to best practices throughout the series of articles we wrote from the documentation for the Azure Public Cloud. The previous article focused on the antipatterns to avoid, specifically the busy database antipattern. This one focuses on busy frontend antipattern.

This antipattern occurs when there are many background threads that can starve foreground tasks of their resources which decreases response times to unacceptable levels. There is a lot of advantages to running background jobs which avoids the interactivity for processing and can be scheduled asynchronously. But the overuse of this feature can hurt performance due to the tasks consuming resources that foreground workers need for interactivity with the user, leading to a spinning wait and frustrations for the user. It appears notably when the foreground is monolithic compressing the business tier with the application frontend. Runtime costs might shoot up if this tier is metered. An application tier may have finite capacity to scale up. Compute resources are better suitable for scale out rather than scale up and one of the primary advantages of a clean separation of layers and components is that they can be hosted even independently. Container orchestration frameworks facilitate this very well. The Frontend can be as lightweight as possible and built on model-view-controller or other such paradigms so that they are not only fast but also hosted on separate containers that can scale out.

This antipattern can be fixed in one of several ways. First the processing can be moved out of the application tier into an Azure Function or some background api layer. If the application frontend is confined to data input and output display operations using only the capabilities that the frontend is optimized for, then it will not manifest this antipattern. APIs and Queries can articulate the business layer interactions. The application then uses the .NET framework APIs to run standard query operators on the data for display purposes.

UI interface is designed for purposes specific to the application. The introduction of long running queries and stored procedures often goes against the benefits of a responsive application. If the processing is already under the control of the application techniques, then they should not be moved. 

Avoiding unnecessary data transfer solves both this antipattern as well as chatty I/O antipattern. When the processing is moved to the business tier, it provides the opportunity to scale out rather than require the frontend to scale up.

Detection of this antipattern is easier with the monitoring tools and the built-in supportability features of the application layer. If the frontend activity reveals significant processing and very low data emission, it is likely that this antipattern is manifesting.

Examine the work performed by the Frontend in terms of latency and page load times which can be narrowed down by callers and scenarios, may reveal just the view models that are likely to be causing this antipattern

Finally, periodic assessments must be performed on the application tier.