Building Isolated Process Azure Functions in .NET 8.0: A Comprehensive Guide

In this comprehensive guide, we'll explore how to build and deploy Azure Functions using the isolated process model in .NET 8.0. We'll cover HTTP triggers, Service Bus integration, Application Insights monitoring, and best practices for production deployments.

Introduction

Azure Functions isolated process model represents a significant evolution in the Azure Functions runtime, offering better control over dependencies, improved performance, and enhanced security through process isolation. With .NET 8.0, we get access to the latest features while maintaining the serverless benefits that Azure Functions provide.

Prerequisites

• Visual Studio 2022 (17.8 or later)
• .NET 8.0 SDK
• Azure subscription
• Azure Functions Core Tools v4.x

Project Setup

Let's create a new Azure Functions project using the isolated process model. We'll implement two different trigger types: HTTP and Service Bus.

bash
func init IsolatedFunctionApp --worker-runtime dotnet-isolated --target-framework net8.0
cd IsolatedFunctionApp

First, let's set up our project structure and dependencies in the .csproj file:

xml
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net8.0</TargetFramework>
    <AzureFunctionsVersion>v4</AzureFunctionsVersion>
    <OutputType>Exe</OutputType>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Worker" Version="1.20.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.Http" Version="3.1.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Extensions.ServiceBus" Version="5.14.1" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.Sdk" Version="1.16.2" />
    <PackageReference Include="Microsoft.ApplicationInsights.WorkerService" Version="2.21.0" />
    <PackageReference Include="Microsoft.Azure.Functions.Worker.ApplicationInsights" Version="1.1.0" />
  </ItemGroup>
</Project>

Implementing the Functions

Let's create two functions: an HTTP-triggered function for API endpoints and a Service Bus-triggered function for message processing.

HTTP-Triggered Function

csharp
using System.Net;
using Microsoft.Azure.Functions.Worker;
using Microsoft.Azure.Functions.Worker.Http;
using Microsoft.Extensions.Logging;

namespace IsolatedFunctionApp;

public class HttpTriggerFunction
{
    private readonly ILogger<HttpTriggerFunction> _logger;

    public HttpTriggerFunction(ILogger<HttpTriggerFunction> logger)
    {
        _logger = logger;
    }

    [Function("ProcessHttpRequest")]
    public async Task<HttpResponseData> RunAsync(
        [HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequestData req)
    {
        _logger.LogInformation("C# HTTP trigger function processed a request.");

        try
        {
            var response = req.CreateResponse(HttpStatusCode.OK);
            await response.WriteAsJsonAsync(new
            {
                message = "Success",
                timestamp = DateTime.UtcNow
            });

            return response;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error processing HTTP request");
            var errorResponse = req.CreateResponse(HttpStatusCode.InternalServerError);
            await errorResponse.WriteAsJsonAsync(new { error = "An error occurred processing your request" });
            return errorResponse;
        }
    }
}

Service Bus-Triggered Function

csharp
using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace IsolatedFunctionApp;

public class ServiceBusFunction
{
    private readonly ILogger<ServiceBusFunction> _logger;

    public ServiceBusFunction(ILogger<ServiceBusFunction> logger)
    {
        _logger = logger;
    }

    [Function("ProcessServiceBusMessage")]
    public async Task RunAsync(
        [ServiceBusTrigger("%ServiceBusQueueName%", Connection = "ServiceBusConnection")] string message)
    {
        try
        {
            _logger.LogInformation("Processing Service Bus message: {Message}", message);
            
            // Add your message processing logic here
            await ProcessMessageAsync(message);
            
            _logger.LogInformation("Successfully processed message");
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error processing message: {Message}", message);
            throw; // Re-throw to trigger the retry policy
        }
    }

    private async Task ProcessMessageAsync(string message)
    {
        // Simulate some processing
        await Task.Delay(100);
    }
}

Program.cs Setup with Application Insights

csharp
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.DependencyInjection;

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults(worker =>
    {
        worker.UseMiddleware<ExceptionHandlingMiddleware>();
    })
    .ConfigureServices(services =>
    {
        services.AddApplicationInsightsTelemetryWorkerService();
        services.ConfigureFunctionsApplicationInsights();
    })
    .Build();

await host.RunAsync();

Custom Middleware for Exception Handling

csharp
public class ExceptionHandlingMiddleware : IFunctionsWorkerMiddleware
{
    private readonly ILogger<ExceptionHandlingMiddleware> _logger;

    public ExceptionHandlingMiddleware(ILogger<ExceptionHandlingMiddleware> logger)
    {
        _logger = logger;
    }

    public async Task Invoke(FunctionContext context, FunctionExecutionDelegate next)
    {
        try
        {
            await next(context);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Unhandled exception in function execution");
            throw;
        }
    }
}

Configuration Setup

Create a local.settings.json file for local development:

json
{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet-isolated",
    "ServiceBusConnection": "<your-service-bus-connection-string>",
    "ServiceBusQueueName": "myqueue",
    "APPLICATIONINSIGHTS_CONNECTION_STRING": "<your-app-insights-connection-string>"
  }
}

Best Practices for Azure Functions

1. Performance Optimization

• Connection Reuse: Implement singleton patterns for client connections (e.g., Service Bus client, HTTP client)
• Proper Scaling Configuration: Set appropriate host.json configurations:

json
{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "excludedTypes": "Request"
      }
    }
  },
  "functionTimeout": "00:10:00",
  "extensions": {
    "serviceBus": {
      "prefetchCount": 100,
      "messageHandlerOptions": {
        "maxConcurrentCalls": 32,
        "maxAutoRenewDuration": "00:05:00"
      }
    }
  }
}

2. Error Handling and Logging

• Implement comprehensive error handling with try-catch blocks
• Use structured logging with appropriate log levels
• Include correlation IDs in logs for request tracking
• Configure proper retry policies for transient failures

3. Security Best Practices

1. Use Managed Identity where possible
2. Store secrets in Azure Key Vault
3. Implement proper authorization levels for HTTP triggers
4. Use private endpoints for enhanced network security

4. Monitoring and Diagnostics

1. Configure Application Insights for comprehensive monitoring
2. Set up appropriate alerts for errors and performance issues
3. Use proper sampling rates to manage costs
4. Implement custom metrics for business-specific monitoring

5. Development and Deployment

1. Use Infrastructure as Code (IaC) with Azure Bicep or ARM templates
2. Implement proper CI/CD pipelines
3. Use staging slots for zero-downtime deployments
4. Maintain separate configurations for different environments

Deployment

Deploy your function app using Azure CLI:

bash
az login
az functionapp create --name myisolatedfunctionapp --storage-account mystorageaccount --resource-group myresourcegroup --runtime dotnet-isolated --runtime-version 8.0 --functions-version 4 --os-type Linux --consumption-plan-location eastus

Monitoring with Application Insights

Access your application's telemetry through the Azure Portal:

1. Navigate to your Function App
2. Click on "Application Insights"
3. Explore metrics, logs, and performance data
4. Set up custom dashboards for monitoring

Conclusion

Isolated process Azure Functions in .NET 8.0 provide a robust foundation for building serverless applications. By following the best practices outlined in this guide and implementing proper monitoring and error handling, you can build reliable and scalable solutions that leverage the full potential of Azure Functions.

Remember to regularly update dependencies, monitor performance metrics, and adjust configurations based on your specific use cases and requirements.