Azure Functions is a serverless compute service that lets you run event-driven code without explicitly provisioning or managing infrastructure. With Azure Functions, you can build applications by running small pieces of code, called "functions," that are triggered by various events. This approach simplifies application development and allows you to focus on writing business logic.

What are Azure Functions?

Azure Functions is a compute-on-demand service that is built on the Azure Functions runtime. The runtime can be hosted on-premises or in the cloud. It allows you to develop and deploy event-driven applications on Azure. Key characteristics include:

• Event-driven: Functions are executed in response to events from Azure services or third-party services.
• Serverless: You don't need to worry about managing servers, operating systems, or patching. Azure handles all the infrastructure.
• Scalable: Azure Functions automatically scales your application based on demand, ensuring performance and availability.
• Cost-effective: You pay only for the compute time consumed by your functions.
• Polyglot: Supports multiple programming languages, including C#, JavaScript, Python, Java, and PowerShell.

Key Concepts

Understanding the core concepts is crucial for leveraging Azure Functions effectively:

Triggers

A trigger defines how a function is invoked. When a trigger event occurs, Azure Functions automatically runs your function code. Common triggers include:

• HTTP Trigger: Invoked by an HTTP request.
• Timer Trigger: Executes on a schedule.
• Blob Trigger: Runs when a blob is added or updated in Azure Blob Storage.
• Queue Trigger: Invoked when a message arrives in an Azure Storage Queue.
• Event Grid Trigger: Responds to events from Azure Event Grid.

Bindings

Bindings provide a declarative way to connect your function code to other Azure services or external data sources. They simplify access to data by reducing the amount of boilerplate code you need to write. Bindings can be used for both input and output:

• Input Bindings: Pass data from an external service into your function.
• Output Bindings: Send data from your function to an external service.

Common Use Cases

Azure Functions are ideal for a wide range of scenarios:

Getting Started with Azure Functions

You can develop Azure Functions using various tools and languages:

• Azure Portal: Create and manage functions directly in your browser.
• Visual Studio Code: A popular, free code editor with excellent Azure Functions extension support.
• Visual Studio: A powerful IDE for C# and .NET development.
• Azure CLI: Command-line interface for managing Azure resources.

To begin, you'll typically need an Azure subscription and the appropriate development tools installed. Start with a simple "Hello World" HTTP trigger to familiarize yourself with the development workflow.

    // Example HTTP Trigger in JavaScript
    module.exports = async function (context, req) {
        context.log('JavaScript HTTP trigger function processed a request.');
        const name = (req.query.name || (req.body && req.body.name));
        const responseMessage = name
            ? "Hello, " + name + "!"
            : "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

        context.res = {
            body: responseMessage
        };
    };
                    

Pricing

Azure Functions offers a consumption plan, which is billed based on the number of executions and the resources consumed (memory and execution time). There's also a premium plan for more predictable costs and advanced features, and a dedicated App Service plan for running functions on your own VMs.

The consumption plan includes a generous free grant of executions and compute time each month, making it very cost-effective for many use cases.