Dockerization

Application Dockerization RuleBook

Core Principles

• Analysis First: Thoroughly examine application before starting work
• User Collaboration: Involve users in decisions, avoid assumptions, confirm critical choices
• Documentation: Record all configurations, generated values, and requirements
• Efficiency: Use available tools and information before requesting input
• Error Analysis: Identify root causes before retrying failed operations

Mandatory 9-Phase Workflow

1. Application Analysis

• Examine directory structure and key files
• Identify programming language, framework, and dependencies
• Document external services (databases, cache, message queues)
• Create file/purpose mapping table
• Accumulate findings progressively

2. Base Image Selection

• Prefer official Docker Hub images
• Choose Alpine/slim variants for smaller size
• Consider security update frequency
• Create comparison table with pros/cons
• Document selection rationale

3. Dockerfile Creation

• Use multi-stage builds when applicable
• Configure non-root user for security
• Optimize layer caching and minimize size
• Implement health checks
• Address security concerns explicitly

4. Docker Compose Configuration

• Include application and dependent services
• Configure networks and volumes properly
• Set environment variables and secrets
• Omit obsolete 'version' attribute
• Enable service dependencies and restart policies

5. Build Process

• Use docker compose build (preferred method)
• Tag images with human-readable names
• Implement comprehensive .dockerignore file
• Document build commands and process
• Handle build errors systematically

6. Container Execution

• Start with docker compose up -d
• Verify all services start successfully
• Apply database migrations if required
• Check container status and logs
• Ensure port mappings work correctly

7. Health Verification

• Check container status and logs
• Test application endpoints (expect 200 status)
• Verify dependent service connectivity
• Monitor resource usage
• Consider network accessibility (avoid localhost assumptions)

8. Resource Cleanup

• Stop containers with docker compose down
• Remove unnecessary volumes and images
• Clean build cache and temporary files
• Document cleanup procedures
• Verify complete resource removal

9. Documentation

• List all required environment variables
• Identify secrets and sensitive configurations
• Document deployment and migration steps
• Provide troubleshooting guidance
• Create final summary report

Security Requirements

• Never run as root user
• Use specific image tags (avoid 'latest')
• Implement proper .dockerignore
• Store secrets securely (not in image layers)
• Scan for vulnerabilities regularly
• Set resource limits appropriately
• Use minimal base images

Error Handling Guidelines

• Build Failures: Analyze error messages, check Dockerfile syntax, verify base image availability
• Runtime Failures: Check logs immediately, verify environment variables, test dependencies
• Performance Issues: Monitor resources, check for leaks, optimize layers
• Never repeat failed commands more than twice without changing approach

Tool Usage (For Agents)

• State objectives before each tool call
• Use generate_code for Dockerfile creation when available
• Leverage persistent scratchpad for state management
• Invoke multiple independent operations simultaneously
• Provide regular progress updates via todo lists

Best Practices Summary

DO:

• Use official base images and specific tags
• Implement health checks and resource limits
• Document thoroughly and test systematically
• Cache dependencies effectively
• Monitor container health continuously

DON'T:

• Run containers as root
• Store secrets in Dockerfiles
• Use 'latest' tags in production
• Skip security scanning
• Ignore error root causes

Success Criteria Checklist

• Container builds successfully
• Application runs without errors
• All health checks pass
• Dependencies properly configured
• Environment variables documented
• Security measures implemented
• Resources cleaned up
• Complete documentation provided
• Build images for the deployment target architecture (most likely amd64, unless the deployment target is arm-based)

Critical Workflow Rules

1. Analysis before action - understand the application first
2. User involvement - confirm decisions and tradeoffs
3. Progressive documentation - record findings at each step
4. Error analysis - identify causes before retry attempts
5. Security by design - implement security measures throughout
6. Health verification - test thoroughly before completion
7. Clean completion - remove unnecessary resources and document fully

Adapt based on specific application requirements and organizational policies. Always prioritize security and maintainability.