aspire-service-defaults

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• SKILL.md

SKILL.md (first lines)

# Aspire Service Defaults

## When to Use This Skill

Use this skill when:
- Building Aspire-based distributed applications
- Need consistent observability (logging, tracing, metrics) across services
- Want shared health check configuration
- Configuring HttpClient resilience and service discovery

---

## What is ServiceDefaults?

ServiceDefaults is a shared project that provides common configuration for all services in an Aspire application:

- **OpenTelemetry** - Logging, tracing, and metrics
- **Health Checks** - Readiness and liveness endpoints
- **Service Discovery** - Automatic service resolution
- **HTTP Resilience** - Retry and circuit breaker policies

Every service references this project and calls `AddServiceDefaults()`.

---

## Project Structure

```
src/
  MyApp.ServiceDefaults/
    Extensions.cs
    MyApp.ServiceDefaults.csproj
  MyApp.Api/
    Program.cs  # Calls AddServiceDefaults()
  MyApp.Worker/
    Program.cs  # Calls AddServiceDefaults()
  MyApp.AppHost/
    Program.cs
```

---

## ServiceDefaults Project

### Project File

```xml
<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>net9.0</TargetFramework>
    <IsAspireSharedProject>true</IsAspireSharedProject>
  </PropertyGroup>

  <ItemGroup>
    <FrameworkReference Include="Microsoft.AspNetCore.App" />
    <PackageReference Include="Microsoft.Extensions.Http.Resilience" />
    <PackageReference Include="Microsoft.Extensions.ServiceDiscovery" />
    <PackageReference Include="OpenTelemetry.Exporter.OpenTelemetryProtocol" />
    <PackageReference Include="OpenTelemetry.Extensions.Hosting" />
    <PackageReference Include="OpenTelemetry.Instrumentation.AspNetCore" />
    <PackageReference Include="OpenTelemetry.Instrumentation.Http" />
    <PackageReference Include="OpenTelemetry.Instrumentation.Runtime" />
  </ItemGroup>
</Project>
```

### Extensions.cs

```csharp
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Diagnostics.HealthChecks;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Diagnostics.HealthChecks;
using Microsoft.Extensions.Logging;
using OpenTelemetry;
using OpenTelemetry.Metrics;
using OpenTelemetry.Trace;

namespace Microsoft.Extensions.Hosting;

public static class Extensions
{
    private const string HealthEndpointPath = "/health";
    private const string AlivenessEndpointPath = "/alive";

    /// <summary>
    /// Adds common Aspire services: OpenTelemetry, health checks,
    /// service discovery, and HTTP resilience.
    /// </summary>
    public static TBuilder AddServiceDefaults<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        builder.ConfigureOpenTelemetry();
        builder.AddDefaultHealthChecks();

        builder.Services.AddServiceDiscovery();

        builder.Services.ConfigureHttpClientDefaults(http =>
        {
            // Resilience: retries, circuit breaker, timeouts
            http.AddStandardResilienceHandler();

            // Service discovery: resolve service names to addresses
            http.AddServiceDiscovery();
        });

        return builder;
    }

    public static TBuilder ConfigureOpenTelemetry<TBuilder>(this TBuilder builder)
        where TBuilder : IHostApplicationBuilder
    {
        // Logging
        builder.Logging.AddOpenTelemetry(logging =>
        {
            logging.IncludeFormattedMessage = true;
            logging.IncludeScopes = true;
        });

From ComeOnOliver/skillshub, MIT.

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