Why and When to use Azure Functions

Mahesh Chand

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Azure FunctionsWhen Azure FunctionsWhy Azure Functions

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Eranda Nandaseana4y ago
As my understanding and experience, Azure function is a perfectly a good solution to build web API and backend API. Event-Driven application might be the ideal candidate for the FaS compute runtime BUT not ONLY candidate application type.1. With the introduction of the Azure function Isolated process, you could get almost all the features available in the dotnet Core we app if you are into DotNet and C# - 2. Azure function is a Microsoft offering of the Serverless Computing model, AWS do have Lamda, I’m trying to point out the serverless is more general computing model for future of the Cloud computing, So we can consider example from the AWS as well. Writing web API on AWS also well supported, Look the Chalice web framework build by AWS specially for lambda https://github.com/aws/chalicehttps://youtu.be/gEiULhbHKQI?t=1215 -- https://docs.microsoft.com/en-us/azure/architecture/reference-architectures/serverless/web-app 3. Azure function and lambda is perfect runtime to build microservices that truly communicate asynchronously each other. Checkout out Azure functions Durable frameworks and AWS step functions to spawn workload from HTTP to background orchestrations 4. Implementing API with Azure functions and Lambda doesn’t necessarily require you to write one function per every API call. It’s depends on the framework you use to implement web API on serverless environment. 5. Cost is mostly depend on hosting model. For instance, consumption-based pricing cost only for your API consumption. So implementing you API as one function app or implementing the same API as 10 function app doesn’t have any significant cost differences.
- Eranda Nandaseana4y ago
  We could build applications using the Azure function runtime and hosted on on-premise VM and containers. But that doesn't mean we are using “Serverless” application. Serverless always comes with public cloud providers that manage infrastructure and resources for us. Cost would be a trade-off for the convenience we get that does not have to worry about the infrastructure requirement for highly dynamic applications. Web sites with “Thousends of call per second” is not that clear for me to get an any idea. :) Some web site do get static assets 80% of the requests (require totally different architecture) some sites do call Rest API 80% of time that truly executes business logic. Application that does thousands of API call (bounded to business logic) per second require better scalability as well, so Serverless would be a good candidate. Azure offer Premium pricing model for the Azure function. It is mix of cost of ownership (like VM) and the consumption based. Might useful for enterprise application that require predictable and controlled cost model yet leverage the benefit of being Serverless
- Mahesh Chand4y ago
  Great points and feedback. Good points. I am going to do some research on cost and serverless. How do you run serverless without using Azure? Can I build Serverless Azure Functions or AWS Lambdas without Azure or AWS? When you have website that has high traffic and there are thousands of calls per second, you can't really use pay-per-use model because it gets costly. We have VMs on Azure. I compare Azure Functions vs API as buying a bottle of water vs a tank of water. I can host a Web API on a VM/IIS and it cost me $0 because I'm paying for the server/VM. Hosting Azure functions, I pay for each call.
Amir Hajiha4y ago
Is Azure Function a good candidate for having microservice pattern or do you still recommend Web APIs?
- Mahesh Chand4y ago
  If you're going with Microservices architecture, Azure functions probably is a good candidate. You'll have to look at your requirements and how much Azure functions are going to cost you. Remember, Azure functions you pay per call and don't pay anything when you don't use. So, its not a good idea to have for high volume transactions and transactions that have a single database. Its not easy to answer but Azure functions are not for everything as detailed in this article.
Hamid Khan5y ago
Very very useful article.............
Steve Montgomery5y ago
Thanks, why are Azure Functions not a replacement for WebAPI? Can they not fulfil the same role? For example why not build a complex command domain api using Azure Functions and API manager to be consumed by a front end CDN? With CQRS I see the advantage or running queries through functions, but am unsure if the Command side architecture should be Azure Functions or WebAPI.The limitations I see are not being able to easily use a third party IoC container for more advanced dependency injection and not having access to HttpContextAccessor to be able to inject user authorisation permissions into a domain layer.
- Mahesh Chand5y ago
  It's no different than buying a 100 gallon tank vs buying individual bottles. While Azure functions sounds a good idea. Imagine a large application that has 100s or more Azure function apps. Not only it becomes a maintenance nightmare but also can get really costly. Remember, Azure functions are designed for cloud only. What if you need to migrate your application to a non cloud native? Like a VM in Azure? For example, in the case of C# Corner, we will pay ton of money to execute Azure functions but in case of Web API, we have a VM running at a fixed cost (as a reservation, 3 yr lock, 75% cost reduction) and adding more functions to our Web API or adding more Web API applications means $0 cost increase. Also, from development side, we have only one project to maintain. At least, that's my understanding when comparing Web API vs Azure Functions. Both have their pros and cons.

Why and When to use Azure Functions

Azure functions and lambda functions are two new serverless technologies that are growing faster than anything else in the cloud development. You can see more and more azure functions applications are being developed every day and there is a fair reason for that. If you are new to Azure functions, I highly recommend reading What is Azure functions.

When architecting a new cloud software or applications, one of the key decisions architects and developers must make is a way to connect to the backend services, running backend tasks, and background processing, and even some simple tasks such as scheduling and sending emails without affecting the main application processing. This is where azure functions app can come handy and useful.

This article focuses on deciding when and why you should use Azure functions instead of Web API and other services.

Before we start with when and why Azure functions, let us try to understand key characteristics of Azure functions.

Azure functions are language independent. Azure functions is a piece of code that is written to do a specific tasks. Azure functions is platform and language agnostic. You can write an Azure functions in one of the popular programming languages including C#, Java, JavaScript, TypeScript, and Python. You can deploy and execute Azure functions on any platform that can run .NET Core.
Azure functions are scalable. Azure functions uses compute-on-demand, which is scalable by design. When demand of execution increases, more resources are allocated automatically to the service and when requests fall, all extra resources and application instances drop off automatically.
Azure functions are lightweight and serverless. An Azure functions app is designed to a specific task and hence it is lightweight by design. Azure functions are serverless and do not require any Web servers or virtual machines to deploy and run.
Azure functions are platform agnostic and run in their own process and environment. You can deploy Azure functions in any kind of configurations including Linux, Windows, or containers but Azure functions are available and can be consumed from any applications as long as they have access to the function.
Azure functions are easier to write and deploy. Because of the nature of the Azure functions, they are easy to code, test, debug, and deploy. You don’t need a large team of developers to do that. A single developer can do everything.
Azure functions are fast to execute because there is no large application, startup time, initialization, and other events fired before the code is executed.
Azure functions’ execution is triggered when an event is fired. Azure functions setup provides dozens of triggers that can be configured when an azure functions is executed.
Azure function can be built, tested, and deployed in Azure portal using a browser.
Azure functions are independent. Azure functions are easy to upgrade and doesn’t affect other parts of a website or other applications.
Azure functions use industry standard and can communicate with other APIs, databases, and libraries. This makes Azure functions more accessible in cloud native applications.
Azure functions can be cost effective because if their nature of running on demand.

When to use Azure Functions?

Azure functions service is a lightweight and serverless compute service that has its own use. You can’t replace a large website with Azure functions.

Here are some of the use cases of Azure functions:

Scheduled Tasks
Reminders and Notifications
Lightweight Web API
Sending background emails
Running background backup tasks
Doing backend calculations

Azure functions are best suited for smaller apps have events that can work independently of other websites. Some of the common azure functions are sending emails, starting backup, order processing, task scheduling such as database cleanup, sending notifications, messages, and IoT data processing.

Let’s say, you have to send a birthday email to your customers. You’re an ASP.NET web developer. Instead of building a website in ASP.NET, deploy and hosting it on IIS, just for one feature, you can simply write an azure function and put your email login in the function and deploy it on azure cloud. The azure functions will direct connect to your data source, get your customers emails, and send them an email on a scheduled date and time.

When not to use Azure Functions?

Azure functions are not for everything. Not all applications should be using Azure functions apps. As I mentioned earlier, Azure functions uses triggers and once an event is triggered, the task will be executed in the background.

Azure functions are not a replacement of Web APIs. If your web applications use Web APIs as middleware to bunch of data and business logic related tasks.
Unlike Web API or services, Azure Functions are not designed to multiple tasks. An Azure functions app should be designed to do one task only.
Azure functions are not designed to work in tightly coupled systems that are dependent on other parts of application.
Azure functions are not for front-end applications where data is being accessed and saved back and forth in the backend databases.
Azure functions should not have too much complex logic in the function code.
Azure functions are compute-on-demand. Replacing an API with bunch of Azure functions apps may increase your cost of development, maintenance, and compute.

To learn more about Azure functions and how create and execute Azure functions, check out: What is Azure Functions

References

https://docs.microsoft.com/en-us/azure/azure-functions/functions-best-practices