File-Based Azure Functions with Aspire

This project demonstrates a file-based Azure Functions application orchestrated using Aspire. It showcases how to model and deploy Azure Functions as individual C# files within an Aspire distributed application.

Overview

This application models file-based Azure Functions apps using a custom Aspire extension. Instead of traditional project-based Functions, each function is defined in a single .cs file with inline package references and dependencies. The Aspire app host orchestrates these functions along with their required infrastructure (Azure Storage).

The project includes two sample functions:

• http.cs: An HTTP-triggered function that responds to GET and POST requests
• timer.cs: A timer-triggered function that executes every 10 seconds

Prerequisites

• .NET 10 SDK (RC 2 or later)
• Aspire 13

Running the Application

Local Development

Run the application locally using the Aspire orchestrator:

aspire run

This command will:

• Start the Aspire dashboard
• Launch the Azure Storage emulator (Azurite)
• Start both function apps (timer and http)
• Provide telemetry and logging through the Aspire dashboard

The Aspire dashboard will be available at http://localhost:17193 (or another port if configured), where you can:

• Monitor function execution
• View logs and traces
• Inspect resource health
• Test HTTP endpoints

Testing the HTTP Function

Once running, the HTTP function will be accessible through the Aspire dashboard's endpoints section. You can send requests to test it:

curl http://localhost:<assigned-port>/api/HttpTriggerImpl

Deploying to Azure

Deploy the application to Azure Container Apps:

aspire deploy

This command will:

• Prompt you to select or create an Azure subscription
• Provision necessary Azure resources (Container App Environment, Storage Account)
• Build and deploy both function apps as containers to ACA Native Functions
• Configure networking and environment variables

After deployment, the command will output the URLs for your deployed functions.

Project Structure

• apphost.cs: The Aspire app host that orchestrates the functions and infrastructure
• http.cs: HTTP-triggered function implementation
• timer.cs: Timer-triggered function implementation
• host.json: Azure Functions host configuration
• local.settings.json: Local development settings
• global.json: .NET SDK version specification

File-Based Functions Model

This project uses a file-based approach to Azure Functions where:

1. Each function is defined in a single .cs file
2. Package references are declared inline using #:package directives
3. The Aspire AddFunctionApp extension method orchestrates the functions
4. Azure Storage is automatically provisioned and configured
5. OpenTelemetry integration is enabled for observability

Custom Extension

The FunctionsExtensions class in apphost.cs provides the AddFunctionApp method that:

• Registers file-based function apps as Aspire resources
• Automatically provisions shared Azure Storage
• Configures Azure Functions runtime settings
• Enables OpenTelemetry for distributed tracing
• Sets up HTTP endpoints for both local and deployed scenarios=