Docker Deploy Skill

Workflow

Phase 1: Analyze the Application

1. Identify the tech stack by examining the project files:

   • Look for package.json (Node.js), requirements.txt / pyproject.toml / Pipfile (Python), go.mod (Go), pom.xml / build.gradle (Java), Cargo.toml (Rust), composer.json (PHP), Gemfile (Ruby), *.csproj (C#/.NET)
   • Check for existing Dockerfile, docker-compose.yml, or .dockerignore
   • Identify the application entry point, build commands, and runtime requirements
   • Detect required services (databases, caches, message queues, etc.)

2. Ask clarifying questions if the following are unclear:

   • Target deployment environment (local dev, staging, production)
   • Required external services (DB, cache, queue, object storage)
   • Domain name and SSL requirements
   • Resource constraints (memory, CPU limits)
   • Whether the user needs a reverse proxy

Phase 2: Generate Dockerfile

Follow these best practices when generating Dockerfiles:

Multi-stage Builds

Always use multi-stage builds for compiled languages and frontend assets to minimize image size.

# Example: Node.js multi-stage
FROM node:20-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci
COPY . .
RUN npm run build

FROM node:20-alpine AS runtime
WORKDIR /app
ENV NODE_ENV=production
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/node_modules ./node_modules
COPY package*.json ./
EXPOSE 3000
USER node
CMD ["node", "dist/index.js"]

Dockerfile Best Practices

• Base image: Use specific version tags (not latest), prefer -alpine or -slim variants
• Layer ordering: Copy dependency manifests first, install dependencies, then copy source code (maximizes layer caching)
• Security: Add a non-root USER directive; never run as root in production
• .dockerignore: Always generate a .dockerignore alongside the Dockerfile
• Health checks: Include HEALTHCHECK instruction when appropriate
• Labels: Add LABEL for maintainer, version, description metadata
• Signal handling: Use exec form for CMD (JSON array syntax) so the process receives signals properly
• Minimize layers: Combine related RUN commands with &&

Stack-Specific Templates

Refer to references/dockerfile-templates.md for ready-to-use Dockerfile templates for each supported stack.

Phase 3: Author Docker Compose File

Use Compose Specification (v3.8+ / compose spec) format.

Compose File Structure

# compose.yml (preferred filename per Compose Specification)