In this lesson, you will learn how to isolate and manage independent application environments within the same Docker Swarm cluster using multiple Compose stacks.
The Concept of Stacks
In Docker Swarm, a "stack" is a collection of services defined in a Compose file that are deployed and managed as a single unit. While you can deploy a single monolithic file, real-world environments often require running multiple independent applications—like a frontend-stack and a backend-api-stack—on the same set of nodes. By using docker stack deploy, you treat these stacks as distinct entities, preventing naming collisions and allowing you to update one application without disrupting the others.
Orchestrating with Compose
When you use a Compose file for Swarm, you aren't just running docker-compose up. Instead, you use the docker stack command, which orchestrates the distribution of these services across your Swarm nodes.
If you have two separate projects, you can define them in separate files and deploy them side-by-side:
# Deploy the web stack
docker stack deploy -c web-stack.yml frontend
# Deploy the database stack
docker stack deploy -c db-stack.yml backend
By providing a name (like frontend or backend) to the deploy command, Swarm creates a unique namespace for each stack. Even if both stacks define a service named app, Docker will resolve them internally as frontend_app and backend_app.
Why This Matters
This approach is essential for modular infrastructure. Because each stack is managed independently, you can:
- Isolate concerns: Keep your database configurations separate from your application logic.
- Granular Control: Perform rolling updates or scale services for one stack without touching the other.
- Shared Networking: If you define a shared overlay network in your files, you can even allow these stacks to communicate securely while remaining logically separate.
By organizing your infrastructure into distinct stacks, you maintain a cleaner, more maintainable cluster that reflects the modularity of your microservices architecture.
Key Takeaway: Orchestrating multi-stack deployments allows you to deploy and manage independent application groups as isolated, scalable units within a single cluster namespace.