Explanations - Understanding-Oriented Documentation

Welcome to the explanations section! This documentation helps you understand the concepts, architecture, and design decisions behind the Qubinode KVM Host Setup Collection.

Note

Need practical guidance? Check out our Tutorials - Learning-Oriented Guides for learning or How-To Guides - Problem-Oriented Solutions for problem-solving.

Understanding the Collection

🏗️ Architecture Overview

System Architecture

High-level design principles, component relationships, and architectural patterns used throughout the collection.

Collection Architecture Overview
🧩 Modular Design

Modular Role Design

Why we chose a modular approach and how it benefits users, developers, and the project ecosystem.

Modular Role Design Philosophy
🤖 Automation Philosophy

Automation Framework

The comprehensive automation philosophy that guides development, testing, and deployment processes.

Automation Philosophy and Framework
📋 Design Decisions

Architecture Decision Records

Detailed records of all major architectural decisions, their context, and consequences.

architecture-decisions/index

Key Concepts

### Architectural Principles

Modularity The collection is built on modular principles where each role has a specific, well-defined responsibility. This enables:

  • Separation of Concerns: Each role focuses on one aspect

  • Reusability: Roles can be used independently or together

  • Maintainability: Changes to one component don’t affect others

  • Testability: Each role can be tested in isolation

Idempotency All operations are designed to be idempotent, meaning:

  • Safe Re-execution: Can be run multiple times safely

  • State Convergence: Brings system to desired state regardless of current state

  • Change Detection: Only makes changes when necessary

Configuration-Driven The collection uses extensive configuration to adapt to different environments:

  • Environment Flexibility: Same code works across dev, staging, production

  • Platform Abstraction: Supports multiple RHEL-based distributions

  • Feature Toggles: Enable/disable features based on requirements

### Design Patterns

Layered Architecture The collection implements a layered architecture:

┌─────────────────────────────────────────┐
│           Orchestration Layer           │
│            (kvmhost_setup)              │
├─────────────────────────────────────────┤
│          Application Layer              │
│    (cockpit, user_config, storage)     │
├─────────────────────────────────────────┤
│         Infrastructure Layer           │
│      (libvirt, networking, base)       │
├─────────────────────────────────────────┤
│           Foundation Layer              │
│        (OS, hardware, services)        │
└─────────────────────────────────────────┘

Event-Driven Communication Roles communicate through Ansible facts and handlers:

  • Facts: Roles set facts that other roles can use

  • Handlers: Asynchronous event handling for service management

  • Dependencies: Clear dependency chains ensure proper execution order

Design Philosophy

### User-Centric Design The collection is designed with users in mind:

  • Simplicity: Complex tasks made simple through automation

  • Flexibility: Configurable for different use cases

  • Reliability: Consistent, predictable behavior

  • Documentation: Comprehensive, user-focused documentation

### Developer-Friendly Architecture The architecture supports effective development:

  • Modularity: Clear separation of concerns

  • Testability: Comprehensive testing framework

  • Extensibility: Easy to add new features

  • Standards: Consistent coding and documentation standards

### Operational Excellence The design supports operational requirements:

  • Automation: Reduced manual intervention

  • Monitoring: Built-in health checks and validation

  • Scalability: Supports growth and expansion

  • Security: Security best practices built-in

Evolution and History

### Project Evolution The collection has evolved through several phases:

  1. Foundation Phase: Basic role structure and core functionality

  2. Enhancement Phase: Advanced features and platform support

  3. Automation Phase: CI/CD integration and automated processes

  4. Documentation Phase: Comprehensive documentation framework

### Key Milestones - Modular Architecture: ADR-0002 established the modular foundation - Testing Framework: ADR-0005 integrated Molecule testing - Platform Support: ADR-0008 extended RHEL 9/10 support - Automation Strategy: ADR-0009 implemented Dependabot automation

### Lessons Learned - Start Simple: Begin with basic functionality, add complexity gradually - Test Early: Comprehensive testing prevents issues - Document Decisions: ADRs capture reasoning behind choices - User Feedback: Regular user feedback drives improvements

Understanding Through Examples

### Architectural Patterns in Action

Dependency Resolution Example:

# kvmhost_setup orchestrates dependencies
dependencies:
  - kvmhost_base          # Foundation
  - kvmhost_networking    # Requires base
  - kvmhost_libvirt      # Requires base + networking
  - kvmhost_storage      # Requires base + libvirt

Configuration Inheritance Example:

# Base role provides foundation
base_packages: [curl, wget, git]

# Libvirt role extends
libvirt_packages: "{{ base_packages + ['libvirt-daemon', 'qemu-kvm'] }}"

# Storage role further extends
storage_packages: "{{ libvirt_packages + ['lvm2', 'parted'] }}"

Research and Analysis

The explanations in this section are based on:

  • Industry Best Practices: Ansible, DevOps, and infrastructure automation standards

  • User Feedback: Real-world usage patterns and requirements

  • Performance Analysis: Benchmarking and optimization research

  • Security Research: Security best practices and compliance requirements