Azure Functions

Azure Functions Development

This skill guides you through building serverless applications with Azure Functions, from local development to production deployment.

When to use this skill

Use this skill when you need to:

• Build event-driven serverless applications
• Create HTTP APIs without managing infrastructure
• Process messages from queues or event hubs
• Schedule recurring tasks with timer triggers
• Implement microservices architecture

Prerequisites

• Azure Functions Core Tools (func --version)
• Azure CLI or Azure subscription access
• Programming language runtime (.NET, Node.js, Python, or Java)
• Storage account for function state (created automatically)

Guidelines

Function App Structure

Organize your Functions project following these patterns:

my-functions/
├── host.json                 # Global configuration
├── local.settings.json       # Local development settings (gitignored)
├── requirements.txt          # Python dependencies
└── MyFunction/
    ├── __init__.py          # Function entry point
    ├── function.json        # Binding configuration
    └── sample.dat           # Test data

Trigger Types and Use Cases

HTTP Triggers - API endpoints and webhooks

# Python example
import azure.functions as func

def main(req: func.HttpRequest) -> func.HttpResponse:
    name = req.params.get('name', 'World')
    return func.HttpResponse(f"Hello, {name}!")

Timer Triggers - Scheduled tasks (cron expressions)

• Format: {second} {minute} {hour} {day} {month} {day-of-week}
• Example: 0 30 9 * * 1-5 (9:30 AM weekdays)

Queue Triggers - Process messages from Azure Storage Queues Event Hub Triggers - Real-time stream processing Blob Triggers - React to file uploads

Development Workflow

Local Development

# Create new function app
func init MyFunctionApp --python

# Create new function
cd MyFunctionApp
func new --name HttpExample --template "HTTP trigger"

# Run locally
func start

# Test locally
curl http://localhost:7071/api/HttpExample?name=Azure

Deployment Options

1. VS Code Extension - Right-click deploy
2. Azure CLI - func azure functionapp publish <app-name>
3. GitHub Actions - CI/CD pipeline
4. Bicep/ARM - Infrastructure as code

Performance Optimization

Cold Start Mitigation

• Use Premium plan for latency-sensitive apps
• Enable Always On (Consumption plan limitation: can't avoid cold starts)
• Use pre-warmed instances in Premium plan

Scaling Considerations

• Design functions to be stateless
• Use output bindings instead of manual SDK calls
• Implement idempotency for queue processing
• Set appropriate maxConcurrentRequests

Security Best Practices

• Use Managed Identity for service authentication
• Store secrets in Azure Key Vault
• Enable Application Insights for monitoring
• Implement input validation on HTTP triggers
• Use HTTPS only (enforced by default)

Examples

See the examples/ directory for:

• http-trigger/ - REST API implementation
• queue-trigger/ - Message processing function
• timer-trigger/ - Scheduled maintenance tasks
• deployment-bicep/ - Infrastructure as code templates

References

• Azure Functions documentation
• Functions triggers and bindings
• Best practices
• Pricing and plans