If you want to start to develop solutions with Azure Functions, you have to know one of the languages Azure Functions supports (at this moment in time, C#, JavaScript, Java, and Python). If you do, you'll easily be able to follow this book.

The Microsoft entry point for the Azure Functions documentation is located at https://azure.microsoft.com/en-us/services/functions/. Starting from there, you can find technical documentation, whitepapers, and samples, and you can navigate to the GitHub repositories for the different tools you'll encounter in this book.

Finally, you can find the source code for this book at https://github.com/PacktPublishing/Mastering-Azure-Serverless-Computing/tree/master/Chapter01.

The Azure Functions platform allows you to run a piece of code (basically a simple function) in response to a wide variety of events; for example, you can run code when a client makes an HTTP request or when someone puts a message into a queue.

There are two fundamental concepts to understand when approaching the world of Azure Functions—triggers and bindings:

• Triggers are what cause a function to run; they define what kind of event the function responds to. A trigger tells you how a function is called, and a function must have exactly one trigger. Triggers have associated data, which is often provided as the payload of the function, and you can use the data contained in the payload to better understand the nature of the event that wakes up your function.
• Bindings are the way functions can exchange data with other cloud services such as...

The Azure Functions runtime (runtime for short) is part of Azure Functions Core Tools, a set of Command-Line Interface (CLI) tools that allow you to run, test, and deploy your functions and that you can install on your PC or server.

There are two versions of Azure Function Core Tools:

• Version 1.x: This version can run only on Windows and supports version 1.x of the Azure Functions runtime. It supports .NET Framework 4.7.1 only.
• Version 2.x: This version can run on Windows, macOS, and Linux and supports the 2.x version of the Azure Functions runtime.

The 2.x version of the tool contains the 2.x version of the Azure Functions runtime. It is based on .NET Core and can run on all platforms that support .NET Core 2.x and 3.x (Windows, macOS, and Linux).

Since 2002, Visual Studio has been the most important IDE for developing solutions with .NET Framework and it is an important tool to use to implement and test your Azure Functions.

In this book, we will always refer to Visual Studio 2019 but most of the operations we will perform on that version can be done on Visual Studio 2017 (Visual Studio 2017 is the oldest version of Visual Studio that supports Azure Functions development).

Visual Studio 2019 allows you to create an Azure Functions project:

1. Simply choose the File | New | Project menu:

2. This menu option opens the Visual Studio project type window where you can choose the Azure Functions project type:

If you don't have the Azure Functions template in the project types list, you probably didn't install the Azure development workload. In this case, you can use the...

If you have worked with SOAP services in your career, surely you have had to deal with the concept of a Web Services Description Language (WSDL) manifest. WSDL is the identity card of a SOAP service and fully describes the service itself in terms of the endpoints, ports, and payloads used by the service. Using WSDL, you can understand how a third-party service works and you can create its client automatically.

The OpenAPI Specification is the counterpart of WSDL for REST API services: they are a set of specifications created by the most important players in the computer science world, such as Google, Microsoft, and IBM which join together in open governance structure under the Linux Foundation. The purpose of the OpenAPI specification is to standardize how REST APIs are described using a programming language-agnostic approach based...

As you have read in the previous paragraphs, you can use the Azure Functions runtime to host your functions, but the host process exposes your function on the localhost, so you cannot reach them from another PC than the one hosting them.

If you want to expose your functions on the internet and, therefore, solve the problem, you can use ngrok. ngrok is software (running on Windows, macOS, and Linux) that allows you to expose a local server to the internet using a secure tunnel, and it also works if your local server is behind a NAT or a firewall.

1. To use ngrok, you need to register yourself on the ngrok website and create an account.

ngrok has a free plan that allows you to use the software for free with the limitation of only one process at a time with a maximum of four tunnels and a random port, but it is enough to test...

Implementing a software solution is only the first step; once you've written your code (or if something goes wrong in your test environment), you need to be able to debug it.

Visual Studio and Visual Studio Code give you all the tools to debug an Azure Function both locally and remotely.

In this section, we will use the features of Visual Studio, but these features are also available in Visual Studio Code.

Using the Visual Studio debugger (or the Visual Studio Code debugger), you can debug your function locally as you do for any other program written in .NET: you can insert breakpoints, run the software step by step, or use the debug console.

The issue, when...

In this chapter, you learned how to create, build, and debug an Azure Function using Azure Functions Core Tools, Visual Studio, and Visual Studio Code. Also, you discovered how to implement the OpenAPI Specification in our HTTP triggered function and how to expose your local functions on the internet using ngrok.

Azure Functions Core Tools is the main tool you can use to create, host, and manage your Azure Functions. Using this tool, you can write Azure Functions in C#, JavaScript, Java, and Python and build and host them in your local development environment. Along with this tool, you can use a whole series of tools that allow you to enhance your development and debugging experience. Of course, a better development experience is provided by using a modern IDE such as Visual Studio or Visual Studio Code but you can write your functions with your favorite IDE and operating...

1. Which of these languages is supported by the Azure Functions runtime?
   • C#
   • Golang
   • JavaScript
   • Java
   • Cobol

2. Which of the following tools can you use to create a project containing an Azure Function?
   • Visual Studio
   • Azure Functions Core Tools
   • Storage Emulator
   • Management Studio

3. Can you create Azure Functions written in different programming languages within a function app?
   • Yes, both in V.1.x and in V2.x
   • Yes, only in V1.x
   • Yes, only in V2.x
   • No, never

4. How can you debug your Azure Functions remotely?
   • By installing Visual Studio in the same VM that hosts the Azure Function.
   • Using the Cloud Explorer extension on Visual Studio and the remote debugger.
   • You can't debug an Azure Function remotely.

You can find more information about developing and debugging Azure Functions at these URLs:

• The Azure Functions portal: https://azure.microsoft.com/en-us/services/functions/
• Work with Azure Functions Core Tools: https://docs.microsoft.com/en-us/azure/azure-functions/functions-run-local
• Code and test Azure Functions locally: https://docs.microsoft.com/en-us/azure/azure-functions/functions-develop-local
• Develop Azure Functions using Visual Studio: https://docs.microsoft.com/en-us/azure/azure-functions/functions-develop-vs
• Visual Studio tutorial - Create your first Azure Function: https://tutorials.visualstudio.com/first-azure-function/intro