Azure Functions Documentation

Introduction to Azure Functions

Azure Functions is a serverless compute service that lets you run event-driven code without explicitly provisioning or managing infrastructure. You pay only for the time your code runs and can scale automatically from zero to planet-scale.

With Azure Functions, you can build applications by connecting to other services, both Azure and third-party. This makes it ideal for tasks like:

Processing data streams
Orchestrating workflows
Building APIs
Running scheduled tasks
Responding to HTTP requests

Key Benefit: Focus on writing code, not managing servers.

Getting Started

To start with Azure Functions, you'll typically need:

An Azure Account.
The Azure Functions Core Tools installed locally.
A preferred development environment (e.g., Visual Studio Code with the Azure Functions extension, Visual Studio, or the Azure CLI).

Creating your First Function

You can create a new Function App project locally. Here's a basic example using the Azure Functions Core Tools CLI:

                $ func init MyFunctionApp --worker-runtime node --language javascript

                $ cd MyFunctionApp

                $ func new --name HttpTrigger --template "HTTP trigger"

This command initializes a new Node.js function app and creates an HTTP-triggered function named HttpTrigger. The generated code typically looks like this:

                // HttpTrigger/index.js

                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!" :

                        "This HTTP triggered function executed successfully. Pass a name in the query string or in the request body for a personalized response.";

                    context.res = {

                        // status: 200, /* Defaults to 200 */

                        body: responseMessage

                    };

                };

Core Concepts

Function App

A Function App is the logical container for your functions. It allows you to group functions, manage their configuration, and deploy them as a single unit.

Triggers

A trigger defines how a function is invoked. It's the event that causes a function to run. Examples include HTTP requests, timer events, or new messages in a queue.

Bindings

Bindings allow your function to connect to other Azure services declaratively, without requiring you to write explicit client SDK code. They simplify input and output operations.

Input Bindings: Provide data to your function.
Output Bindings: Send data from your function to another service.

Bindings reduce the amount of code you need to write for common integration scenarios.

Triggers and Bindings

Triggers and bindings are the core of Azure Functions' event-driven model. They allow you to connect your code to various services and events.

Common Triggers

HTTP Trigger: Invokes your function via an HTTP request.
Timer Trigger: Runs your function on a schedule.
Blob Trigger: Runs your function when a blob is added or updated in Azure Blob Storage.
Queue Trigger: Runs your function in response to a message appearing in an Azure Storage Queue.
Cosmos DB Trigger: Runs your function when documents are created or updated in Cosmos DB.

Common Bindings

Azure Table Storage: Input and output binding for Azure Table Storage.
Service Bus: Input and output binding for Azure Service Bus queues and topics.
Event Hubs: Input and output binding for Azure Event Hubs.
DocumentDB/Cosmos DB: Input and output binding for Azure Cosmos DB.

For example, to bind to a Cosmos DB input, your function definition might look like this (in function.json):

                {

                  "scriptFile": "index.js",

                  "bindings": [

                    {

                      "name": "inputDocument",

                      "type": "cosmosDB",

                      "direction": "in",

                      "databaseName": "myDatabase",

                      "collectionName": "myCollection",

                      "connectionStringSetting": "CosmosDBConnection"

                    },

                    {

                      "name": "$return",

                      "type": "http",

                      "direction": "out"

                    }

                  ]

                }

Supported Languages

Azure Functions supports a variety of programming languages, allowing you to use your preferred tools and skills:

C#
JavaScript
TypeScript
Python
Java
PowerShell
Custom Handlers (for Go, Rust, and others)

You choose a runtime when you create your Function App, and each language has specific considerations for development and deployment.

Deployment

Azure Functions can be deployed in several ways:

Azure CLI: Use the az functionapp create command.
Visual Studio Code: The Azure Functions extension provides a seamless deployment experience.
Visual Studio: Publish directly from Visual Studio to Azure.
Azure DevOps / GitHub Actions: Integrate deployment into your CI/CD pipelines for automated deployments.
Zip Deploy: Upload a zip file containing your function code.

Deployment Slots

Use deployment slots to deploy new versions of your function app to a staging environment, test them, and then swap them into production with no downtime.

Monitoring

Monitoring your functions is crucial for understanding performance, debugging issues, and ensuring reliability.

Application Insights

Azure Functions integrates seamlessly with Application Insights, Azure's application performance management (APM) service. You can:

Track function executions, durations, and success rates.
View logs and exceptions.
Set up alerts for critical errors.
Analyze performance metrics.

Live Metrics

Get real-time insights into your function's performance directly in the Azure portal.

Pricing

Azure Functions offers a consumption-based pricing model, meaning you only pay for the compute time you consume.

Consumption Plan: You're billed based on the number of executions and the execution time (GB-seconds). A generous free grant is provided each month.
Premium Plan: Offers pre-warmed instances for zero-cold-start execution, VNet connectivity, and longer runtimes, with predictable costs.
App Service Plan: Run Functions on existing App Service plans for predictable costs and dedicated resources.

Choose the plan that best fits your application's needs for performance, scalability, and cost.

For detailed pricing information, please visit the official Azure Functions pricing page.