Azure Functions is a serverless compute service that's used to run small pieces of code in the cloud. You can simply write the code you need in order to execute a certain task, without the need to create a whole application or manage your own infrastructure.
Azure Functions can be created from the Azure portal and from Visual Studio 2019 and can be created in a variety of programming languages. At the time of writing this book, the following languages are supported:
| Language | 1.x | 2.x | 3.x |
|---|---|---|---|
| C# | GA (.NET Framework 4.7) | GA (.NET Core 2.2) | Preview (.NET Core 3.1) |
| JavaScript | GA (Node 6) | GA (Node 8 and 10) | GA (Node 8 and 10) |
| F# | GA (.NET Framework 4.7) | GA (.NET Core 2.2) | GA (.NET Core 3.1) |
| Java | N/A | GA (Java 8) | GA (Java 8) |
| PowerShell | N/A | GA (PowerShell Core 6) | GA (PowerShell Core 6) |
| Python | N/A | GA (Python 3.6 and 3.7) | GA (Python 3.6 and 3.7) |
| TypeScript | N/A | GA (Supported through transpiling to JavaScript) | GA (Supported through transpiling to JavaScript) |
Functions can be created using ARM templates as well. They can be deployed on Windows or Linux and by using continuous deployment. At the time of writing this book, Linux is still in preview.
With Azure Functions, you can build solutions that process data, integrate various systems, work with the Internet of Things (IoT), and simple APIs and microservices applications. You can create a small task, such as image or order processing, and call this task from other applications or execute it based on a certain schedule. For that, Azure Functions provides triggers such as HTTPTrigger, TimerTrigger, CosmosDBTrigger, BlobTrigger, QueueTrigger, EventGridTrigger, EventHubTrigger, ServiceBusQueueTrigger, and ServiceBusTopicTrigger.
Azure Functions uses an Azure storage account to store any code files and configuration bindings. It uses the standard Azure Storage, which provides blob, table, and queue storage for storing the files and triggers. However, you can use the same App Service plans for the functions that you use for web apps and APIs. Azure Functions can also be deployed in App Service environments (ASEs). When using these App Service plans or an ASE to host your functions, the function will become non-serverless. This happens due to the compute power being prelocated and therefore prepaid.