Observability101-Demo

A simple .NET 10 demo showcasing basic observability (OpenTelemetry) with a Postgres database and the Microsoft Aspire dashboard.

Getting started

Prerequisites:

• Docker Desktop (or compatible Docker engine)
• .NET SDK 10.0 (to run the app locally)
• Free local ports: 18888 (Aspire dashboard), 4317 (OTLP gRPC), 15432 (Postgres)

1) Start infrastructure with Docker Compose

From the repository root:

• Start containers (Aspire + Postgres):
  • Windows PowerShell: docker compose up -d
• Stop containers: docker compose down
• Stop and remove data volume: docker compose down -v (this clears the database)

What gets started:

• Aspire Dashboard: http://localhost:18888
• OTLP gRPC ingest (mapped to host): http://localhost:4317
• Postgres: Host=localhost; Port=15432; Db=obs-example-db; User=obs-example; Password=obs-example-password

You can open the Aspire dashboard at http://localhost:18888 to observe traces, logs, and metrics once the app is running.

2) Run the application

Run the API locally with .NET (Development profile):

• Windows PowerShell (from repo root): dotnet run --project .\Observability101

The API will listen on:

• http://localhost:5036
• Swagger UI: http://localhost:5036/swagger

Note:

• The app is configured to export telemetry to OTLP using the values in Observability101/appsettings.Development.json:
  • OTEL_EXPORTER_OTLP_ENDPOINT: http://localhost:4317
  • OTEL_EXPORTER_OTLP_PROTOCOL: grpc
• On startup (Demo only), the database is dropped and re-created automatically.

3) Generate some activity

Use Swagger at http://localhost:5036/swagger to call endpoints and generate traces/metrics/logs. Then switch to the Aspire dashboard (http://localhost:18888) to view activity.

Troubleshooting

• If you don’t see telemetry in Aspire:
  • Ensure Docker containers are running: docker ps should show the Aspire and Postgres containers.
  • Verify OTLP endpoint and protocol in Observability101/appsettings.Development.json.
  • Ensure port 4317 is not blocked by a firewall and that the Aspire container is exposing ingestion (compose maps host 4317 to container 18889).
• If the API cannot connect to Postgres, confirm the database container is healthy and that port 15432 is free.

Useful commands

• Rebuild containers after changes: docker compose up -d --pull always
• View container logs:
  • Aspire: docker logs obs101-aspire-container
  • Postgres: docker logs obs101-postgres-container