Docker and Containerization for Agentic Dev

Why Containerize?

Containers solve critical problems for AI-assisted development:

1. Reproducibility - AI generates code for your environment, not theirs
2. Isolation - Mistakes can't break your system
3. Consistency - Same environment across team members
4. Portability - Move between machines seamlessly

Docker Installation Check

Development Dockerfile Pattern

For Node.js projects, use this development Dockerfile:

dockerfile
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# Dockerfile.dev
FROM node:22-alpine

WORKDIR /app

# Install dependencies first (better caching)
COPY package*.json ./
RUN npm ci

# Copy source code
COPY . .

# Development port
EXPOSE 3000

# Enable hot reloading
ENV WATCHPACK_POLLING=true

CMD ["npm", "run", "dev"]

Docker Compose for Development

yaml
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# docker-compose.yml
services:
  web:
    build:
      context: .
      dockerfile: Dockerfile.dev
    ports:
      - "3000:3000"
    volumes:
      # Mount source for hot reloading
      - .:/app
      # Don't override node_modules
      - /app/node_modules
    environment:
      - NODE_ENV=development

Production Dockerfile Pattern

Multi-stage build for optimized production images:

dockerfile
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# Dockerfile.prod
# Stage 1: Dependencies
FROM node:22-alpine AS deps
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production

# Stage 2: Build
FROM node:22-alpine AS builder
WORKDIR /app
COPY --from=deps /app/node_modules ./node_modules
COPY . .
RUN npm run build

# Stage 3: Run
FROM node:22-alpine AS runner
WORKDIR /app
ENV NODE_ENV=production

# Security: non-root user
RUN addgroup --system --gid 1001 nodejs
RUN adduser --system --uid 1001 nextjs
USER nextjs

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

EXPOSE 3000
CMD ["node", "server.js"]

Workflow Commands

Prompting AI for Container-Aware Code

When asking AI to generate code, include container context:

I'm running in a Docker container (node:22-alpine).

I need to implement {{feature}}.

Constraints:
- Use only Alpine-compatible packages
- Assume the app runs as non-root user
- Environment variables come from docker-compose
- File paths should be container-relative (/app/...)

Please account for these in your implementation.

Common Docker Issues

Container Security for AI Work

Safety checklist:

• Non-root user in containers
• No --privileged flag
• Minimal base images (alpine)
• No secrets in Dockerfile
• Use .dockerignore

.dockerignore Best Practices

# .dockerignore
node_modules
.next
.git
.env
.env.local
*.md
Dockerfile*
docker-compose*

Verify

Your containerized setup is correct if:

• docker-compose up starts the dev server
• Code changes trigger hot reload
• docker-compose down cleans up completely
• Production image is under 200MB
• Container runs as non-root

Next: Integrate AI tools with your IDE for seamless development.