docker-composer

Docker Composer Skill

Core Workflows

Workflow 1: Primary Action

1. Analyze the input and context
2. Validate prerequisites are met
3. Execute the core operation
4. Verify the output meets expectations
5. Report results

Overview

This skill helps you create efficient Docker configurations for development and production. Covers Dockerfiles, Docker Compose, multi-stage builds, networking, volumes, and container orchestration best practices.

Docker Philosophy

Container Principles

1. One process per container: Keep containers focused
2. Immutable infrastructure: Don't modify running containers
3. Stateless containers: Store state in volumes or external services
4. Minimal images: Smaller = faster + more secure

Best Practices

• DO: Use multi-stage builds for production
• DO: Pin specific versions for dependencies
• DO: Use .dockerignore to exclude unnecessary files
• DO: Run as non-root user
• DON'T: Store secrets in images or Dockerfiles
• DON'T: Use latest tag in production
• DON'T: Install unnecessary packages

Dockerfile Patterns

Node.js Production Dockerfile

# Dockerfile
# ============================================
# Stage 1: Dependencies
# ============================================
FROM node:20-alpine AS deps
WORKDIR /app

# Install dependencies only when needed
COPY package.json package-lock.json ./
RUN npm ci --only=production

# ============================================
# Stage 2: Builder
# ============================================
FROM node:20-alpine AS builder
WORKDIR /app

COPY package.json package-lock.json ./
RUN npm ci

COPY . .

# Build application
ENV NEXT_TELEMETRY_DISABLED 1
RUN npm run build

# ============================================
# Stage 3: Runner (Production)
# ============================================
FROM node:20-alpine AS runner
WORKDIR /app

ENV NODE_ENV production
ENV NEXT_TELEMETRY_DISABLED 1

# Create non-root user
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs

# Copy built assets
COPY --from=builder /app/public ./public
COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static

USER nextjs

EXPOSE 3000

ENV PORT 3000
ENV HOSTNAME "0.0.0.0"

CMD ["node", "server.js"]