# Docker Swarm Stack Skill

Use this skill when adding, reviewing, or modifying Docker Swarm stack files in this repository.

## Workflow

1. Confirm the service belongs in the Swarm repo.
2. Create or update a Swarm-compatible stack YAML file.
3. Create or update `.env.example` with placeholders only.
4. Use Docker secrets/configs for sensitive runtime values.
5. Define overlay networks and named volumes explicitly.
6. Add `deploy:` settings only when they are meaningful.
7. Validate YAML/Compose rendering where possible.
8. Explain deployment commands, required secrets, required networks, and rollback notes.

## Swarm Standards

- Use 2-space YAML indentation.
- Prefer explicit image tags over unpinned `latest` when stability matters.
- Use `deploy.restart_policy` for Swarm-managed services.
- Use `placement.constraints` when a service must run on a specific node or node label.
- Do not use `container_name`; it is ignored or problematic in Swarm.
- Be careful with `depends_on`; Swarm does not honor Compose startup ordering the same way local Compose does.
- Prefer external secrets for sensitive values.

## Validation Command Pattern

```bash
docker compose --env-file <service>.env.example -f <stack-file>.yml config
```

Do not run `docker stack deploy` unless explicitly asked.