# Dotnet Aspire Patterns > Using .NET Aspire. AppHost orchestration, service discovery, components, dashboard, health checks. - Skill: `wshaddix/dotnet-aspire-patterns` (Agent Skill) - Install (CLI): `npx skillmds add wshaddix/dotnet-aspire-patterns` - Raw SKILL.md: https://api.skillmd.com/api/skills/wshaddix/dotnet-aspire-patterns/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Product & Planning - Author: wshaddix (https://skillmd.com/u/wshaddix) - Updated: 2026-09-09 - Page: https://skillmd.com/skills/wshaddix/dotnet-aspire-patterns --- # dotnet-aspire-patterns .NET Aspire orchestration patterns for building cloud-ready distributed applications. Covers AppHost configuration, service discovery, the component model for integrating backing services (databases, caches, message brokers), the Aspire dashboard for local observability, distributed health checks, and when to choose Aspire vs manual container orchestration. **Out of scope:** Raw Dockerfile authoring and multi-stage builds -- see [skill:dotnet-containers]. Kubernetes manifests, Helm charts, and Docker Compose -- see [skill:dotnet-container-deployment]. OpenTelemetry SDK configuration and custom metrics -- see [skill:dotnet-observability]. DI service lifetime mechanics -- see [skill:dotnet-csharp-dependency-injection]. Background service hosting -- see [skill:dotnet-background-services]. Cross-references: [skill:dotnet-containers] for container image optimization and base image selection, [skill:dotnet-container-deployment] for production Kubernetes/Compose deployment, [skill:dotnet-observability] for OpenTelemetry details beyond Aspire defaults, [skill:dotnet-csharp-dependency-injection] for DI fundamentals, [skill:dotnet-background-services] for hosted service lifecycle patterns. --- ## Aspire Overview .NET Aspire is an opinionated stack for building observable, production-ready distributed applications. It provides: - **Orchestration** -- define your distributed topology in C# (the AppHost) - **Components** -- pre-configured NuGet packages for common backing services - **Service Defaults** -- shared configuration for OpenTelemetry, health checks, resilience - **Dashboard** -- local development UI for traces, logs, metrics, and resource status Aspire is not a deployment target. It orchestrates the local development and testing experience. For production, it generates manifests consumed by deployment tools (Azure Developer CLI, Kubernetes, etc.). ### When to Use Aspire | Scenario | Recommendation | |----------|---------------| | Multiple .NET services + backing infrastructure | Aspire AppHost -- simplifies local dev and service wiring | | Single API with a database | Optional -- Aspire adds overhead for simple topologies | | Non-.NET services only (Node, Python) | Aspire can reference container images, but the tooling benefit is reduced | | Need Kubernetes/Compose for local dev already | Evaluate migration cost; Aspire replaces docker-compose for dev scenarios | | Team needs consistent observability defaults | Aspire ServiceDefaults standardize OTel across all projects | --- ## AppHost Configuration The AppHost is a .NET project (`Aspire.Hosting.AppHost` SDK) that defines the distributed application topology. It references other projects and backing services, wiring them together with service discovery. ### AppHost Project Setup ```xml Exe net10.0 true ``` ### Defining the Topology ```csharp var builder = DistributedApplication.CreateBuilder(args); // Backing services -- Aspire manages containers automatically var postgres = builder.AddPostgres("pg") .WithPgAdmin() // Adds pgAdmin UI container .AddDatabase("ordersdb"); var redis = builder.AddRedis("cache") .WithRedisCommander(); // Adds Redis Commander UI var rabbitmq = builder.AddRabbitMQ("messaging") .WithManagementPlugin(); // Adds RabbitMQ management UI // Application projects -- wired with service discovery var api = builder.AddProject("api") .WithReference(postgres) .WithReference(redis) .WithReference(rabbitmq) .WithExternalHttpEndpoints(); // Marks endpoints as public in deployment manifests builder.AddProject("worker") .WithReference(postgres) .WithReference(rabbitmq) .WaitFor(api); // Start worker after API is healthy builder.Build().Run(); ``` ### Resource Lifecycle `WaitFor` controls startup ordering. Resources wait until dependencies report healthy before starting: ```csharp // Worker waits for both the database and API to be ready builder.AddProject("worker") .WithReference(postgres) .WaitFor(postgres) // Wait for database container health check .WaitFor(api); // Wait for API health endpoint ``` Without `WaitFor`, resources start in parallel. Use it only when startup order matters (e.g., a worker that requires the database schema to exist). --- ## Service Discovery Aspire automatically configures service discovery so projects can resolve each other by resource name rather than hardcoded URLs. ### How It Works 1. The AppHost injects endpoint information as environment variables and configuration 2. The `Aspire.ServiceDefaults` project configures `Microsoft.Extensions.ServiceDiscovery` 3. Application code resolves services by name via `HttpClient` or connection strings ### Consuming Discovered Services ```csharp // In MyApi/Program.cs var builder = WebApplication.CreateBuilder(args); // AddServiceDefaults registers service discovery, OpenTelemetry, health checks builder.AddServiceDefaults(); // HttpClient resolves "worker" via service discovery builder.Services.AddHttpClient("worker-client", client => { client.BaseAddress = new Uri("https+http://worker"); }); ``` The `https+http://` scheme prefix tells the service discovery provider to try HTTPS first, falling back to HTTP. This is the recommended pattern for inter-service communication in Aspire. ### Connection Strings For backing services (databases, caches), Aspire injects connection strings via the standard `ConnectionStrings` configuration section: ```csharp // AppHost: .WithReference(postgres) on the API project // injects ConnectionStrings__ordersdb automatically // In MyApi/Program.cs builder.AddNpgsqlDbContext("ordersdb"); // Resolves ConnectionStrings:ordersdb from configuration ``` --- ## Component Model Aspire components are NuGet packages that provide pre-configured client integrations for backing services. They handle connection management, health checks, telemetry, and resilience. ### Hosting Packages vs Client Packages | Package Type | Installed In | Purpose | |---|---|---| | `Aspire.Hosting.*` | AppHost project | Define and configure the resource (container, connection) | | `Aspire.* (client)` | Service projects | Consume the resource with health checks and telemetry | ```xml ``` ### Common Components | Component | Hosting Package | Client Package | |-----------|----------------|----------------| | PostgreSQL (EF Core) | `Aspire.Hosting.PostgreSQL` | `Aspire.Npgsql.EntityFrameworkCore.PostgreSQL` | | PostgreSQL (Npgsql) | `Aspire.Hosting.PostgreSQL` | `Aspire.Npgsql` | | Redis (caching) | `Aspire.Hosting.Redis` | `Aspire.StackExchange.Redis` | | Redis (output cache) | `Aspire.Hosting.Redis` | `Aspire.StackExchange.Redis.OutputCaching` | | RabbitMQ | `Aspire.Hosting.RabbitMQ` | `Aspire.RabbitMQ.Client` | | Azure Service Bus | `Aspire.Hosting.Azure.ServiceBus` | `Aspire.Azure.Messaging.ServiceBus` | | SQL Server (EF Core) | `Aspire.Hosting.SqlServer` | `Aspire.Microsoft.EntityFrameworkCore.SqlServer` | | MongoDB | `Aspire.Hosting.MongoDB` | `Aspire.MongoDB.Driver` | ### Client Registration ```csharp var builder = WebApplication.CreateBuilder(args); builder.AddServiceDefaults(); // Each Add* method registers the client, health check, and telemetry builder.AddNpgsqlDbContext("ordersdb"); builder.AddRedisClient("cache"); builder.AddRabbitMQClient("messaging"); ``` Component `Add*` methods: 1. Register the client/DbContext in DI 2. Add a health check for the resource 3. Configure OpenTelemetry instrumentation for the client 4. Apply default resilience settings (retries, timeouts) --- ## Service Defaults The `ServiceDefaults` project is a shared library referenced by all service projects. It standardizes cross-cutting concerns. ### What ServiceDefaults Configures ```csharp public static class Extensions { public static IHostApplicationBuilder AddServiceDefaults( this IHostApplicationBuilder builder) { // Service discovery builder.ConfigureOpenTelemetry(); builder.AddDefaultHealthChecks(); builder.Services.AddServiceDiscovery(); // Resilience for HttpClient builder.Services.ConfigureHttpClientDefaults(http => { http.AddStandardResilienceHandler(); http.AddServiceDiscovery(); }); return builder; } public static IHostApplicationBuilder ConfigureOpenTelemetry( this IHostApplicationBuilder builder) { builder.Logging.AddOpenTelemetry(logging => { logging.IncludeFormattedMessage = true; logging.IncludeScopes = true; }); builder.Services.AddOpenTelemetry() .WithMetrics(metrics => metrics .AddAspNetCoreInstrumentation() .AddHttpClientInstrumentation() .AddRuntimeInstrumentation()) .WithTracing(tracing => tracing .AddAspNetCoreInstrumentation() .AddGrpcClientInstrumentation() .AddHttpClientInstrumentation()); builder.AddOpenTelemetryExporters(); return builder; } public static IHostApplicationBuilder AddDefaultHealthChecks( this IHostApplicationBuilder builder) { builder.Services.AddHealthChecks() .AddCheck("self", () => HealthCheckResult.Healthy()); return builder; } public static WebApplication MapDefaultEndpoints( this WebApplication app) { app.MapHealthChecks("/health"); app.MapHealthChecks("/alive", new HealthCheckOptions { Predicate = r => r.Tags.Contains("live") }); return app; } } ``` ### Using ServiceDefaults Every service project references the ServiceDefaults project and calls the extension methods: ```csharp var builder = WebApplication.CreateBuilder(args); builder.AddServiceDefaults(); // ... service-specific registrations var app = builder.Build(); app.MapDefaultEndpoints(); // ... middleware and endpoints app.Run(); ``` --- ## Dashboard The Aspire dashboard provides a local observability UI that starts automatically with the AppHost. It displays: - **Resources** -- status of all projects, containers, and executables - **Console logs** -- aggregated stdout/stderr from all resources - **Structured logs** -- OpenTelemetry log records with structured properties - **Traces** -- distributed traces across all services - **Metrics** -- real-time metric charts ### Accessing the Dashboard When you run the AppHost (`dotnet run --project MyApp.AppHost`), the dashboard URL is printed to the console: ``` info: Aspire.Hosting.DistributedApplication[0] Login to the dashboard at https://localhost:17043/login?t= ``` ### Dashboard in Non-Aspire Projects The dashboard is available as a standalone container for projects not using the full Aspire stack: ```bash docker run --rm -it -p 18888:18888 -p 4317:18889 \ -d --name aspire-dashboard \ mcr.microsoft.com/dotnet/aspire-dashboard:9.1 ``` Configure your app to export OTLP telemetry to `http://localhost:4317` and view it at `http://localhost:18888`. --- ## Health Checks and Distributed Tracing ### Component Health Checks Each Aspire component automatically registers health checks. The AppHost uses these to determine resource readiness: ```csharp // In AppHost -- WaitFor uses health checks to gate startup builder.AddProject("api") .WithReference(postgres) .WaitFor(postgres); // Waits for Npgsql health check to pass ``` ### Custom Health Checks Add application-specific health checks alongside Aspire defaults: ```csharp builder.Services.AddHealthChecks() .AddCheck( "order-processing", tags: ["ready"]); ``` See [skill:dotnet-observability] for detailed health check patterns (liveness vs readiness, custom checks, health check publishing). ### Distributed Tracing Integration Aspire configures OpenTelemetry tracing through ServiceDefaults. Traces propagate automatically across HTTP boundaries. For custom spans: ```csharp private static readonly ActivitySource s_activitySource = new("MyApp.Orders"); public async Task ProcessOrderAsync(CreateOrderRequest request, CancellationToken ct) { using var activity = s_activitySource.StartActivity("ProcessOrder"); activity?.SetTag("order.customer_id", request.CustomerId); // Calls to other Aspire services carry trace context automatically var inventory = await _httpClient.GetFromJsonAsync( $"https+http://inventory-api/api/stock/{request.ProductId}", ct); // ... process order return order; } ``` See [skill:dotnet-observability] for comprehensive distributed tracing guidance (custom ActivitySource, trace context propagation, span events). --- ## Container Resources ### Adding Container Images For services not available as Aspire components, add arbitrary container images: ```csharp var seq = builder.AddContainer("seq", "datalust/seq") .WithHttpEndpoint(port: 5341, targetPort: 80) .WithEnvironment("ACCEPT_EULA", "Y"); // Reference the container from a project builder.AddProject("api") .WithReference(seq); ``` ### Persistent Volumes By default, Aspire containers use ephemeral storage. Add volumes for data persistence across restarts: ```csharp var postgres = builder.AddPostgres("pg") .WithDataVolume("pg-data") // Named volume for data persistence .AddDatabase("ordersdb"); ``` ### External Resources Reference existing infrastructure not managed by Aspire: ```csharp // Connection string from configuration (not an Aspire-managed container) var existingDb = builder.AddConnectionString("legacydb"); builder.AddProject("api") .WithReference(existingDb); ``` --- ## Aspire vs Manual Container Orchestration | Concern | Aspire | Docker Compose / Manual | |---------|--------|------------------------| | Configuration language | C# (strongly typed) | YAML | | Service discovery | Automatic (env var injection) | Manual DNS/env config | | Health checks | Automatic per component | Manual HEALTHCHECK per service | | Observability | Pre-configured OTel + dashboard | Manual OTel collector setup | | IDE integration | Hot reload, F5 debugging | Attach debugger manually | | Production deployment | Generates manifests (AZD, K8s) | Write manifests directly | | Non-.NET services | Container references (less integrated) | Equal support for all languages | | Learning curve | .NET-specific abstractions | Industry-standard tooling | Choose Aspire when your stack is primarily .NET and you want standardized observability, service discovery, and a simplified local dev experience. Choose manual orchestration when you need fine-grained control, polyglot services, or your team is already proficient with Compose/Kubernetes. --- ## Key Principles - **AppHost is dev-time only** -- it orchestrates local development, not production deployment - **Use components over raw connection strings** -- components add health checks, telemetry, and resilience automatically - **ServiceDefaults is non-negotiable** -- every Aspire service project must reference it for consistent observability - **WaitFor for ordered startup** -- use it for real dependencies (schema migrations, seed data), not for every resource - **Do not duplicate OTel config** -- Aspire ServiceDefaults configure OpenTelemetry; manual configuration causes double-collection --- ## Agent Gotchas 1. **Do not manually configure OpenTelemetry in Aspire service projects** -- ServiceDefaults already registers OTel providers. Adding manual `.AddOpenTelemetry()` calls causes duplicate trace/metric collection and inflated telemetry costs. 2. **Do not hardcode connection strings in Aspire service projects** -- use `builder.AddNpgsqlDbContext("name")` or `builder.Configuration.GetConnectionString("name")`. Aspire injects connection strings via environment variables; hardcoded values bypass service discovery. 3. **Do not use `WaitFor` on every resource** -- it serializes startup and increases launch time. Use it only when a service genuinely cannot start without the dependency (e.g., database migration on startup). 4. **Do not reference `Aspire.Hosting.*` packages from service projects** -- hosting packages belong in the AppHost only. Service projects use client packages (`Aspire.Npgsql`, `Aspire.StackExchange.Redis`, etc.). 5. **Do not confuse the AppHost with a production host** -- the AppHost runs locally (or in CI) to orchestrate resources. Production deployment uses generated manifests or infrastructure-as-code. 6. **Do not omit `AddServiceDefaults()` in new service projects** -- without it, the project lacks service discovery, health checks, and telemetry, breaking Aspire integration silently. --- ## Prerequisites - .NET 10 SDK (or .NET 8/9 with Aspire workload) - Docker Desktop or Podman (for container resources) - Aspire workload: `dotnet workload install aspire` --- ## References - [.NET Aspire overview](https://learn.microsoft.com/en-us/dotnet/aspire/get-started/aspire-overview) - [.NET Aspire components](https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/components-overview) - [.NET Aspire service discovery](https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/service-discovery) - [.NET Aspire dashboard](https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/dashboard/overview) - [.NET Aspire orchestration](https://learn.microsoft.com/en-us/dotnet/aspire/fundamentals/app-host-overview) - [Aspire samples repository](https://github.com/dotnet/aspire-samples)