Multi-Container Workspaces

Overview

Multi-container workspaces use Docker Compose to run sidecar services (databases, caches, queues) alongside the main dev container. The dev container connects to sidecars over the Compose network, giving you a production-like topology in development.

Basic Setup

docker-compose.yml

services:
  app:
    build:
      context: .
      dockerfile: .devcontainer/Dockerfile
    volumes:
      - ..:/workspace:cached
    command: sleep infinity

  db:
    image: postgres:16
    restart: unless-stopped
    environment:
      POSTGRES_USER: dev
      POSTGRES_PASSWORD: devpass
      POSTGRES_DB: myapp
    volumes:
      - pgdata:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine
    restart: unless-stopped

volumes:
  pgdata:

devcontainer.json

{
  "name": "Full Stack App",
  "dockerComposeFile": "docker-compose.yml",
  "service": "app",
  "workspaceFolder": "/workspace",
  "runServices": ["app", "db", "redis"],
  "shutdownAction": "stopCompose",
  "forwardPorts": [3000, "db:5432", "redis:6379"],
  "postCreateCommand": "npm ci && npm run db:migrate",
  "remoteEnv": {
    "DATABASE_URL": "postgresql://dev:devpass@db:5432/myapp",
    "REDIS_URL": "redis://redis:6379"
  }
}

Key Properties

Property	Description
dockerComposeFile	Path(s) to Compose file(s). Can be a string or array.
service	The service to attach the editor to (your dev container).
workspaceFolder	Path inside the container where the repo is mounted.
runServices	Which services to start. Omit to start all.
shutdownAction	stopCompose (stop all) or none (leave running).
forwardPorts	Forward ports; use "service:port" for sidecar ports.

Multiple Compose Files

Override the base Compose file with a dev-specific overlay:

{
  "dockerComposeFile": [
    "docker-compose.yml",
    "docker-compose.dev.yml"
  ],
  "service": "app"
}

The dev overlay can add volumes, environment variables, or features only needed in development.

Compose Override Example

# docker-compose.dev.yml
services:
  app:
    volumes:
      - ..:/workspace:cached
    environment:
      - ASPNETCORE_ENVIRONMENT=Development
    command: sleep infinity

Service Networking

All services in the same Compose file share a network. Reference sidecars by their service name:

• db:5432 — PostgreSQL
• redis:6379 — Redis
• rabbitmq:5672 — RabbitMQ
• azurite:10000 — Azure Storage emulator

No localhost — always use the service name as the hostname.

Health Checks and Dependencies

Ensure sidecars are ready before running setup commands:

services:
  db:
    image: postgres:16
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U dev"]
      interval: 5s
      timeout: 3s
      retries: 5

  app:
    depends_on:
      db:
        condition: service_healthy

Parallel postCreateCommand

Run multiple setup steps concurrently:

{
  "postCreateCommand": {
    "backend": "dotnet restore",
    "frontend": "npm ci",
    "migrations": "npm run db:migrate",
    "seed": "npm run db:seed"
  }
}

Best Practices

• Always use "shutdownAction": "stopCompose" to clean up sidecar containers when the Codespace stops.
• Use named volumes for database data so it survives container rebuilds.
• Add health checks to sidecar services and depends_on with condition: service_healthy for the app service.
• Reference sidecars by service name, never localhost — they are separate containers on the Compose network.
• Keep sidecar images pinned to major versions (e.g., postgres:16, not postgres:latest) for reproducibility.
• Use remoteEnv for connection strings so they are available in the integrated terminal.
• Separate dev-only configuration into a docker-compose.dev.yml overlay to keep production Compose files clean.