experto-docker

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• SKILL.md

SKILL.md (first lines)

## Cuando usar

Usa esta skill para Dockerfile multi-stage, compose local y debug de contenedores.
Cubre builds, imagenes livianas, redes, volumenes, seguridad y health checks.
Para K8s, CI/CD, rollback y estrategias de deploy usa `patrones-despliegue`.
No uses esta skill para pipelines ni orquestacion productiva.

## Multi-Stage Builds

### Node.js

```dockerfile
FROM node:22-alpine AS base
RUN corepack enable pnpm
WORKDIR /app
COPY package.json pnpm-lock.yaml ./

FROM base AS deps
RUN pnpm install --frozen-lockfile --prod

FROM base AS builder
COPY . .
RUN pnpm install --frozen-lockfile
RUN pnpm build

FROM node:22-alpine AS runner
RUN addgroup -g 1001 appgroup && adduser -u 1001 -G appgroup -s /bin/sh -D appuser
WORKDIR /app
ENV NODE_ENV=production
COPY --from=deps --chown=appuser:appgroup /app/node_modules ./node_modules
COPY --from=builder --chown=appuser:appgroup /app/dist ./dist
COPY --from=builder --chown=appuser:appgroup /app/package.json ./
USER appuser
EXPOSE 3000
HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:3000/health || exit 1
CMD ["node", "dist/server.js"]
```

### Python

```dockerfile
FROM python:3.12-slim AS builder
WORKDIR /app
COPY requirements.txt .
RUN pip install --no-cache-dir --user -r requirements.txt

FROM python:3.12-slim
RUN useradd -m appuser
WORKDIR /app
COPY --from=builder /root/.local /home/appuser/.local
COPY --chown=appuser:appuser . .
USER appuser
ENV PATH=/home/appuser/.local/bin:$PATH
CMD ["python", "-m", "app.main"]
```

## Image Optimization

```dockerfile
# Layer caching: copy dependency files first
COPY package.json pnpm-lock.yaml ./
RUN pnpm install --frozen-lockfile
COPY . .

# .dockerignore
node_modules
.git
.env*
*.md
dist
coverage
```

### Size Comparison

| Base | Size |
|------|------|
| `node:22` | ~1.1GB |
| `node:22-slim` | ~250MB |
| `node:22-alpine` | ~180MB |
| `gcr.io/distroless/nodejs22` | ~130MB |

## Docker Compose

### Development

```yaml
services:
  app:
    build:
      context: .
      target: builder
    ports: ["3000:3000"]
    volumes:
      - .:/app
      - app_node_modules:/app/node_modules
    environment:
      NODE_ENV: development
      DATABASE_URL: postgres://user:pass@db:5432/app_dev
    depends_on:
      db: { condition: service_healthy }
      redis: { condition: service_healthy }

  db:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: user
      POSTGRES_PASSWORD: pass
      POSTGRES_DB: app_dev
    ports: ["5432:5432"]
    volumes: [pgdata:/var/lib/postgresql/data]
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U user"]
      interval: 5s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine

From tontojil/PerfeckCode, MIT.

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