Microsoft Docs

Develop Azure Functions

This document provides a comprehensive guide to developing Azure Functions, covering various aspects from project setup to advanced development patterns.

Introduction to Azure Functions Development

Azure Functions is a serverless compute service that enables you to run small pieces of code, or "functions," in the cloud without managing infrastructure. You can develop functions using your preferred programming language and integrate them with a wide range of Azure services and third-party data sources.

Supported Languages

Azure Functions supports a variety of programming languages, allowing you to choose the one that best suits your needs and team expertise. The primary languages supported are:

• C#
• JavaScript
• TypeScript
• Python
• Java
• PowerShell
• Custom Handlers (for other languages)

Each language has its own set of tooling and development patterns. For example, C# functions often leverage .NET, while JavaScript and Python have dedicated runtime environments.

Azure Functions Project Structure

An Azure Functions project typically has a defined structure to organize your code, configurations, and dependencies. A common project structure looks like this:

.
├── MyFunctionProject/
│   ├── host.json             (Global configuration for the function app)
│   ├── local.settings.json   (Local development settings, including connection strings)
│   ├── .gitignore
│   ├── run.csx (or .js, .py, etc.) (Your function code)
│   ├── function.json         (Function-specific configuration for triggers and bindings)
│   └── package.json          (Node.js project file, if applicable)
│   └── ... other function folders
│       └── ...
└── .vscode/                  (VS Code specific settings, optional)
    └── settings.json
                

The host.json file configures the Azure Functions host, while local.settings.json stores application settings, connection strings, and other configurations for local development. Each function typically resides in its own folder, containing its code file and a function.json file that defines its triggers and input/output bindings.

Triggers and Bindings

Triggers initiate the execution of an Azure Function, while bindings connect your function to other Azure services and data sources. This declarative approach simplifies integration and reduces boilerplate code.

Common Triggers:

• HTTP Trigger: Executes in response to an HTTP request.
• Timer Trigger: Executes on a schedule (e.g., every 5 minutes).
• Queue Trigger: Executes when a new message arrives in an Azure Storage Queue.
• Blob Trigger: Executes when a new or updated blob is detected in an Azure Storage container.
• Cosmos DB Trigger: Executes when changes are detected in a Cosmos DB collection.

Common Bindings:

• Input Bindings: Read data from an external service (e.g., an Azure Storage table, a Cosmos DB document).
• Output Bindings: Write data to an external service (e.g., sending a message to an Azure Service Bus, writing to a database).

The function.json file defines these triggers and bindings. For example, a simple HTTP-triggered function might have:

{
  "scriptFile": "run.js",
  "bindings": [
    {
      "authLevel": "function",
      "type": "httpTrigger",
      "direction": "in",
      "name": "req",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "type": "http",
      "direction": "out",
      "name": "res"
    }
  ]
}
                

Local Development

Azure Functions Core Tools provide a robust environment for developing and testing your functions locally on your machine before deploying them to Azure. This includes debugging, running your functions, and simulating triggers.

To get started with local development:

1. Install Azure Functions Core Tools: Refer to the official documentation for installation instructions for your operating system.
2. Create a new project: Use the func init command.
3. Create a new function: Use the func new command.
4. Run your functions: Execute func start in your project directory.

Deployment

Azure Functions can be deployed to Azure using various methods:

• Azure CLI: Use commands like az functionapp create and func azure functionapp publish.
• Visual Studio / VS Code: Integrated deployment tools in IDEs.
• Azure DevOps / GitHub Actions: CI/CD pipelines for automated deployments.
• Containerization: Deploy functions as Docker containers.

Monitoring Functions

Monitoring is crucial for understanding the performance and health of your Azure Functions. Azure Monitor and Application Insights provide comprehensive tools for logging, tracing, and analyzing function executions.

• Application Insights: Offers real-time telemetry, performance monitoring, and error tracking.
• Azure Monitor Logs: Query logs using Kusto Query Language (KQL) for detailed insights.
• Diagnostic Settings: Configure which logs and metrics are sent to various destinations.

Custom Handlers

If you're using a language not natively supported, you can use custom handlers. This involves creating an executable that your Azure Functions host can invoke, which then handles the incoming requests and binds data.

Continue exploring the documentation to delve deeper into specific triggers, bindings, programming models, and best practices for developing robust and scalable serverless applications with Azure Functions.