README.md

Service Defaults aka Smart Defaults

Introduction

Aspire provides a set of smart defaults for services that are commonly used in .NET applications. These defaults are designed to help you get started quickly and provide a consistent experience across different types of applications. This includes:

• Telemetry: Metrics, Tracing, Logging
• Resiliency
• Health Checks
• Service Discovery

Create Service Defaults Project

Visual Studio & Visual Studio Code

1. Add a new project to the solution called ServiceDefaults:

   • Right-click on the solution and select Add > New Project.
   • Select the Aspire Service Defaults project template.
   • Name the project ServiceDefaults.
   • Click Next > Create.

   Visual Studio

   Visual Studio Code

Command Line

1. Create a new project using the dotnet new aspire-servicedefaults command:

   dotnet new aspire-servicedefaults -n ServiceDefaults

   Aspire CLI Tip: You can also use aspire add from within your project to interactively add service defaults and other integrations. The CLI will guide you through selecting the right packages.

Configure Service Defaults

Before we dive into the mechanics, here’s why we do each of the next steps:

• Add project references: This lets the Api and MyWeatherHub projects consume the shared configuration, resilience, telemetry, and discovery wiring that lives in the new ServiceDefaults project without repeating that setup in every service.
• Call builder.AddServiceDefaults(): This opt‑in extension applies the opinionated “smart defaults” (OpenTelemetry logging/tracing/metrics, health checks, service discovery, and resilient HTTP handlers) so you start with production‑minded behavior immediately.
• Call app.MapDefaultEndpoints(): This maps development‑time health endpoints (/health, /alive) and prepares the app for later dashboard and orchestration scenarios. We’ll go deeper into these concepts in later modules; for now just know this lights up diagnostics and readiness probes early.

1. Add a reference to the ServiceDefaults project in the Api and MyWeatherHub projects:

   • Right-click on the Api project and select Add > Reference.
     • Check the ServiceDefaults project and click OK.
   • Right-click on the MyWeatherHub project and select Add > Reference.
     • Check the ServiceDefaults project and click OK.

   Pro Tip: In Visual Studio 2026, you can drag and drop the project onto another project to add a reference.

2. In both the Api and MyWeatherHub projects, update their Program.cs files, adding the following line immediately after their var builder = WebApplication.CreateBuilder(args); line:

   builder.AddServiceDefaults();

3. In both the Api and MyWeatherHub projects, update their Program.cs files,adding the following line immediately after their var app = builder.Build(); line:

   app.MapDefaultEndpoints();

Run the application

1. Run the application using a multiple-project launch configuration in Visual Studio or Visual Studio Code:

   • Visual Studio: Right click on the MyWeatherHub solution and go to properties. Select the Api and MyWeatherHub as startup projects, select OK.
     • 
     • Click Start to start and debug both projects.
   • Visual Studio Code: Run the Api and MyWeatherHub projects using the Run and Debug panel. We have provided a launch.json file with the necessary configurations to run both.

2. Test the application by navigating to the following URLs:

   • https://localhost:7032/openapi/v1.json - API OpenAPI document
   • https://localhost:7274/ - MyWeatherHub

3. You should see the OpenAPI document (JSON) for the API and the MyWeatherHub home page.

4. You can also view the health checks for the API by navigating to https://localhost:7032/health.

5. You can also view the health checks for the MyWeatherHub by navigating to https://localhost:7274/health.

6. View the logs in the terminal to see the health checks and other telemetry data such as resiliency with Polly:

   Polly: Information: Execution attempt. Source: '-standard//Standard-Retry', Operation Key: '', Result: '200', Handled: 'False', Attempt: '0', Execution Time: '13.0649'

7. Click on 5 different cities and a "random" error will be thrown. You will see the Polly retry policy in action.

   Polly: Warning: Execution attempt. Source: '-standard//Standard-Retry', Operation Key: '', Result: '500', Handled: 'True', Attempt: '0', Execution Time: '9732.8258'
   Polly: Warning: Resilience event occurred. EventName: 'OnRetry', Source: '-standard//Standard-Retry', Operation Key: '', Result: '500'
   System.Net.Http.HttpClient.NwsManager.ClientHandler: Information: Sending HTTP request GET http://localhost:5271/forecast/AKZ318

Next: Module #3 - Dashboard & App Host