Agent skill

docker-infra

Docker and Docker Compose configuration and troubleshooting. Use for containers, services, volumes, networking, health checks, and deployment patterns.

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Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/devops/docker-infra-krazyuniks-guitar-tone-shootout

SKILL.md

Docker & Infrastructure Skill

Activation: Docker, Docker Compose, containers, services, deployment

Development Environment

Services Overview

Service Port Image Purpose
backend 8000 python:3.14-slim FastAPI with uvicorn --reload
frontend 4321 node:22-alpine Astro dev server
worker - python:3.14-slim TaskIQ workers
db 5432 postgres:17-alpine PostgreSQL database
redis 6379 redis:7-alpine Job queue + cache

Quick Commands

bash
# Start all services
docker compose up

# Start specific service
docker compose up backend

# Rebuild after dependency changes
docker compose build backend
docker compose up backend

# View logs
docker compose logs -f backend worker

# Shell into container
docker compose exec backend bash
docker compose exec frontend sh

# Stop all
docker compose down

# Stop and remove volumes (reset DB)
docker compose down -v

Dockerfile Patterns

Backend (Python)

dockerfile
# backend/Dockerfile.dev
FROM python:3.14-slim

WORKDIR /app

# System dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential \
    libpq-dev \
    && rm -rf /var/lib/apt/lists/*

# Install uv for fast dependency management
COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv

# Copy dependency files
COPY pyproject.toml uv.lock ./

# Install dependencies
RUN uv sync --frozen

# Copy source (volumes override in dev)
COPY . .

# Run with hot-reload
CMD ["uv", "run", "uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000", "--reload"]

Frontend (Node.js)

dockerfile
# frontend/Dockerfile.dev
FROM node:22-alpine

WORKDIR /app

# Install pnpm
RUN corepack enable && corepack prepare pnpm@latest --activate

# Copy dependency files
COPY package.json pnpm-lock.yaml ./

# Install dependencies
RUN pnpm install --frozen-lockfile

# Copy source (volumes override in dev)
COPY . .

# Run dev server
CMD ["pnpm", "dev", "--host", "0.0.0.0"]

Production (Multi-stage)

dockerfile
# backend/Dockerfile
FROM python:3.14-slim AS builder

WORKDIR /app
COPY --from=ghcr.io/astral-sh/uv:latest /uv /usr/local/bin/uv
COPY pyproject.toml uv.lock ./
RUN uv sync --frozen --no-dev

FROM python:3.14-slim

WORKDIR /app
RUN apt-get update && apt-get install -y --no-install-recommends libpq5 \
    && rm -rf /var/lib/apt/lists/*

COPY --from=builder /app/.venv /app/.venv
COPY . .

ENV PATH="/app/.venv/bin:$PATH"
CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]

Docker Compose Patterns

Development Compose

yaml
# docker-compose.yml
services:
  backend:
    build:
      context: ./backend
      dockerfile: Dockerfile.dev
    ports:
      - "8000:8000"
    volumes:
      - ./backend:/app
      - backend-cache:/app/.venv
    environment:
      - DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/shootout
      - REDIS_URL=redis://redis:6379
    depends_on:
      db:
        condition: service_healthy
      redis:
        condition: service_started

  frontend:
    build:
      context: ./frontend
      dockerfile: Dockerfile.dev
    ports:
      - "4321:4321"
    volumes:
      - ./frontend:/app
      - frontend-node-modules:/app/node_modules
    environment:
      - PUBLIC_API_URL=http://localhost:8000

  worker:
    build:
      context: ./backend
      dockerfile: Dockerfile.dev
    command: uv run taskiq worker app.tasks:broker
    volumes:
      - ./backend:/app
      - ./pipeline:/pipeline:ro
    environment:
      - DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/shootout
      - REDIS_URL=redis://redis:6379
    depends_on:
      - db
      - redis

  db:
    image: postgres:17-alpine
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres
      POSTGRES_DB: shootout
    ports:
      - "5432:5432"
    volumes:
      - postgres-data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U postgres"]
      interval: 5s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    volumes:
      - redis-data:/data

volumes:
  postgres-data:
  redis-data:
  backend-cache:
  frontend-node-modules:

Environment Variables

bash
# .env.example
# Database
DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/shootout
POSTGRES_USER=postgres
POSTGRES_PASSWORD=postgres
POSTGRES_DB=shootout

# Redis
REDIS_URL=redis://redis:6379

# Tone 3000 OAuth
TONE3000_CLIENT_ID=your_client_id
TONE3000_CLIENT_SECRET=your_client_secret
TONE3000_REDIRECT_URI=http://localhost:8000/auth/callback

# Frontend
PUBLIC_API_URL=http://localhost:8000

Networking

Service Discovery

Services communicate using service names as hostnames:

  • Backend → DB: postgresql://postgres:5432
  • Backend → Redis: redis://redis:6379
  • Frontend → Backend: http://backend:8000 (internal)
  • Browser → Backend: http://localhost:8000 (external)

Port Mapping

yaml
ports:
  - "host:container"
  - "8000:8000"  # Accessible from host at localhost:8000

Expose vs Ports

yaml
# Expose: Internal only (other containers)
expose:
  - "5432"

# Ports: External (host machine)
ports:
  - "5432:5432"

Volume Patterns

Named Volumes (Persistent)

yaml
volumes:
  postgres-data:  # Database files
  redis-data:     # Redis persistence

Bind Mounts (Development)

yaml
volumes:
  - ./backend:/app           # Source code (hot-reload)
  - ./pipeline:/pipeline:ro  # Read-only access

Anonymous Volumes (Cache)

yaml
volumes:
  - /app/node_modules  # Preserve installed dependencies
  - /app/.venv         # Preserve Python venv

Health Checks

yaml
db:
  healthcheck:
    test: ["CMD-SHELL", "pg_isready -U postgres"]
    interval: 5s
    timeout: 5s
    retries: 5
    start_period: 10s

backend:
  healthcheck:
    test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
    interval: 30s
    timeout: 10s
    retries: 3

Troubleshooting

Container Won't Start

bash
# Check logs
docker compose logs backend

# Check container status
docker compose ps

# Rebuild from scratch
docker compose build --no-cache backend

Hot-reload Not Working

bash
# Verify volume mount
docker compose exec backend ls -la /app

# Check file permissions
docker compose exec backend stat /app/app/main.py

# Restart service
docker compose restart backend

Database Connection Issues

bash
# Check if DB is healthy
docker compose ps db

# Check DB logs
docker compose logs db

# Verify network
docker compose exec backend ping db

# Test connection
docker compose exec backend python -c "
import asyncpg
import asyncio
asyncio.run(asyncpg.connect('postgresql://postgres:postgres@db:5432/shootout'))
"

Reset Everything

bash
# Stop all containers
docker compose down

# Remove all volumes
docker compose down -v

# Remove all images
docker compose down --rmi all

# Fresh start
docker compose build --no-cache
docker compose up

Production Patterns

Multi-stage Builds

See Dockerfile examples above for smaller production images.

Resource Limits

yaml
services:
  backend:
    deploy:
      resources:
        limits:
          cpus: '1.0'
          memory: 512M
        reservations:
          cpus: '0.25'
          memory: 128M

Logging

yaml
services:
  backend:
    logging:
      driver: "json-file"
      options:
        max-size: "10m"
        max-file: "3"

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