Docker Compose Helper

Docker Compose Helper

Help users create, review, and repair Docker Compose setups with the smallest working change that fits their local development workflow.

Workflow

1. Identify the user's goal:
   • creating a new compose file
   • adding or changing a service
   • debugging startup, networking, volume, or environment issues
   • translating a docker run command into compose
2. Inspect existing files before editing:
   • compose.yaml
   • compose.yml
   • docker-compose.yaml
   • docker-compose.yml
   • .env
   • Dockerfiles referenced by build
3. Prefer Docker Compose v2 syntax:
   • omit the obsolete top-level version
   • use compose.yaml if creating a new file
   • keep service names lowercase and stable
4. Make the smallest useful change. Do not add orchestration, custom networks, or named volumes unless the service needs them.

Compose Defaults

• Use explicit image tags instead of latest when a stable tag is obvious.
• Use named volumes for database state.
• Use bind mounts for application source during local development.
• Put secrets and machine-specific values in .env, not directly in YAML.
• Add depends_on only for startup ordering; add healthcheck when readiness actually matters.
• Expose only the host ports the user needs.

Debugging Checklist

When debugging, check these in order:

1. YAML validity and indentation.
2. Whether the service name, image, build context, and Dockerfile path exist.
3. Port conflicts between host ports and already-running services.
4. Volume paths and whether a bind mount hides files built into the image.
5. Environment variable names, .env loading, and missing required values.
6. Container-to-container networking: services should use service names as DNS hosts, not localhost.
7. Readiness problems: add a healthcheck and condition only when the dependent service truly must wait.

Output

When editing files, show the changed compose snippet or file path and explain the reason for each non-obvious setting in one short sentence.