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How to Prepare Your Application for CWCloud Deployment

Introduction​

This tutorial covers the essential steps to prepare any application for deployment on CWCloud. You'll learn how to:

  • Containerize your application properly
  • Set up automated builds and deployments
  • Follow best practices for production-ready applications
  • Avoid common pitfalls that waste time during deployment

Prerequisites​

  • Docker ≥ 20.10 for containerization
  • Git for version control
  • Basic understanding of your application's runtime requirements

1. Application Preparation Checklist​

For Python Applications​

  • requirements.txt: Create a requirements file that have all installed and used packages, and pin specific versions (flask==2.3.0 not flask)
  • Environment variables: Use .env files for configuration
  • WSGI server: Use production servers like Gunicorn, uWSGI, or Waitress

For Node.js Applications​

  • package-lock.json: Always commit lockfiles for reproducible builds
  • Production dependencies: Separate dev and prod dependencies
  • Build process: Define clear build scripts in package.json

For Other Languages​

  • Dependency files: Include language-specific lock files (Gemfile.lock, composer.lock, go.mod, etc.)
  • Build tools: Ensure build processes are documented and automated
  • Static assets: Pre-build and optimize static files

2. Dockerfile Best Practices​

Multi-stage Build Pattern​

# Build stage
FROM node:18-alpine AS builder
WORKDIR /app
COPY package*.json ./
RUN npm ci --only=production
COPY . .
RUN npm run build

# Production stage
FROM nginx:alpine
COPY --from=builder /app/dist /usr/share/nginx/html
# Configure your web server
COPY nginx.conf /etc/nginx/conf.d/default.conf
EXPOSE 80

Key Principles​

  • Layer caching: Copy dependency files first, then source code
  • Security: Use non-root users when possible
  • Size optimization: Use alpine images and multi-stage builds
  • Health checks: Include HEALTHCHECK instructions
  • Proper ports: Use EXPOSE to document which ports your app uses

3. Database and Data Persistence​

Database Preparation​

# docker-compose.yml example
services:
  app:
    build: .
    environment:
      - DATABASE_URL=postgresql://user:pass@db:5432/myapp
    depends_on:
      - db
  
  db:
    image: postgres:15
    environment:
      - POSTGRES_DB=myapp
      - POSTGRES_USER=user
      - POSTGRES_PASSWORD=pass
    volumes:
      - db_data:/var/lib/postgresql/data

volumes:
  db_data:

Best Practices​

  • Environment variables: Never hardcode database credentials
  • Migration scripts: Include database setup/migration commands
  • Data volumes: Use named volumes for data persistence
  • Backups: Plan for data backup and recovery

4. Configuration Management​

Environment Variables​

# .env file
DATABASE_URL=postgresql://localhost/myapp
SECRET_KEY=your-secret-key
DEBUG=false
PORT=8000

Configuration Files​

  • Use environment-specific configs (development, staging, production)
  • Keep sensitive data in environment variables
  • Provide sensible defaults
  • Document all required environment variables

5. CI/CD Pipeline Setup​

Basic GitLab CI/CD Structure​

stages:
  - test
  - build
  - deploy

variables:
  DOCKER_HOST: tcp://docker:2375/
  DOCKER_TLS_CERTDIR: ""

services:
  - docker:dind

test:
  stage: test
  script:
    - # Run your tests here
    - echo "Running application tests"

build:
  stage: build
  script:
    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
    - docker build -t $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA .
    - docker push $CI_REGISTRY_IMAGE:$CI_COMMIT_SHA

deploy:
  stage: deploy
  script:
    - # Deploy to CWCloud
    - echo "Deploying to production"
  only:
    - main

Pipeline Best Practices​

  • Testing first: Always run tests before building
  • Image tagging: Use commit SHA or semantic versioning
  • Conditional deploys: Only deploy from specific branches
  • Secret management: Use CI/CD variables for sensitive data

6. Common Issues and Solutions​

Build Failures​

  • Missing dependencies: Ensure all dependency files are committed
  • Wrong base image: Choose appropriate base images for your runtime
  • Build context: Use .dockerignore to exclude unnecessary files
  • Memory limits: Large builds might need more memory allocation

Runtime Issues​

  • Port conflicts: Ensure your app listens on the correct port
  • File permissions: Use appropriate user permissions in containers
  • Health checks: Implement proper health endpoints
  • Logging: Configure proper logging to stdout/stderr

Performance Optimization​

  • Image size: Use multi-stage builds and alpine images
  • Caching: Leverage Docker layer caching
  • Resource limits: Set appropriate CPU and memory limits
  • Static assets: Use CDN or optimize asset delivery

7. Testing Your Setup​

Local Testing​

# Test your Docker build
docker build -t myapp .
docker run -p 8000:8000 myapp

# Test with docker-compose
docker-compose up --build

# Test production-like environment
docker-compose -f docker-compose.prod.yml up

Validation Checklist​

  • Application starts without errors
  • All endpoints respond correctly
  • Database connections work
  • Environment variables are loaded
  • Logs are visible and informative
  • Health checks pass

8. Next Steps​

Once your application is properly containerized and tested:

  1. Push to GitLab: Ensure your repository includes all necessary files
  2. Configure CI/CD: Set up your pipeline variables
  3. Deploy to CWCloud: Use the CWCloud deployment tools
  4. Monitor: Set up monitoring and alerting

Tips for Success​

  • Start simple: Begin with basic containerization, then add complexity
  • Documentation: Document your deployment process for team members
  • Version control: Tag releases and maintain changelog
  • Security: Regularly update base images and dependencies
  • Monitoring: Plan for logging, metrics, and alerting from the start

Remember: The goal is to make your application deployment predictable and reproducible. Invest time in proper preparation to save hours during deployment and maintenance.