Architecture Documentation in Magento 2

ADR Template

# ADR-001: Use Elasticsearch for Product Search

## Status
Accepted (2024-01-15)

## Context
Our store has 500K+ products. MySQL full-text search is slow and lacks features like faceted search and relevance tuning.

## Decision
We will use Elasticsearch 7.x for product search.

## Rationale
- Native Magento support
- Handles faceted search
- Better relevance tuning
- Proven at scale

## Alternatives
### MySQL Full-Text Search
- Pros: No additional infrastructure
- Cons: Limited features, poor performance at scale
- Decision: Rejected - won't scale

### Algolia
- Pros: Managed service, great features
- Cons: Vendor lock-in, cost
- Decision: Rejected - too expensive

## Consequences
+ Better search performance
+ Faceted search support
+ Relevance tuning
- Additional infrastructure to maintain
- Team training required

## Follow-up
- [ ] Set up Elasticsearch cluster
- [ ] Configure indexing
- [ ] Train team

ADR Best Practices

1. One decision per ADR
2. Keep it short (1-2 pages)
3. Include status and date
4. Document rejected alternatives
5. Link to related ADRs
6. Review periodically

ADR Index

# Architecture Decision Records

| ADR | Title | Status | Date |
|-----|-------|--------|------|
| 001 | Use Elasticsearch | Accepted | 2024-01-15 |
| 002 | Implement Redis Caching | Accepted | 2024-02-01 |
| 003 | Strangler Fig Migration | Proposed | 2024-03-10 |

When to Write ADRs

- Choosing a technology
- Establishing a pattern
- Making a trade-off decision
- Changing architecture
- Documenting why NOT to do something

Diagram Types

System Context Diagram

┌─────────────┐     ┌─────────────┐     ┌─────────────┐
│   Customer  │────▶│   Magento   │────▶│  Payment    │
│             │     │   Store     │     │  Gateway    │
└─────────────┘     └─────────────┘     └─────────────┘
                           │
                           â–¼
                    ┌─────────────┐
                    │  Database   │
                    └─────────────┘

Container Diagram

┌─────────────────────────────────────────────────────────┐
│                    Magento Application                   │
├─────────────┬─────────────┬─────────────┬───────────────┤
│   Web       │   API       │   Admin     │   Queue       │
│   Frontend  │   Backend   │   Panel     │   Workers     │
├─────────────┴─────────────┴─────────────┴───────────────┤
│              Shared Services Layer                       │
├─────────────┬─────────────┬─────────────┬───────────────┤
│   Catalog   │   Orders    │   Customers │   Search      │
│   Service   │   Service   │   Service   │   Service     │
└─────────────┴─────────────┴─────────────┴───────────────┘

Component Diagram

┌─────────────────────────────────────────┐
│          Order Processing               │
├─────────────────────────────────────────┤
│  ┌───────────┐  ┌───────────┐          │
│  │  Order    │  │  Payment  │          │
│  │  Service  │──│  Service  │          │
│  └───────────┘  └───────────┘          │
│       │              │                 │
│       ▼              ▼                 │
│  ┌───────────┐  ┌───────────┐          │
│  │  Inventory│  │  Email    │          │
│  │  Service  │  │  Service  │          │
│  └───────────┘  └───────────┘          │
└─────────────────────────────────────────┘

Diagram Tools

Text-based:
- Mermaid (markdown compatible)
- PlantUML
- Graphviz/DOT

Visual:
- Draw.io (free)
- Lucidchart
- Figma

Code:
- D2 (modern)
- Structurizr (C4 model)

Mermaid Example

graph TD
    A[Customer] --> B[Magento Frontend]
    B --> C[API Gateway]
    C --> D[Order Service]
    C --> E[Catalog Service]
    D --> F[Payment Gateway]
    D --> G[Database]
    E --> G

Diagram Best Practices

1. Keep it simple
2. Use consistent notation
3. Include legend
4. Version your diagrams
5. Update when architecture changes
6. Link to related ADRs

Documentation Hierarchy

docs/
├── README.md                    # Project overview
├── ARCHITECTURE.md              # High-level architecture
├── decisions/                   # ADRs
│   ├── 001-use-elasticsearch.md
│   └── 002-redis-caching.md
├── guides/                      # How-to guides
│   ├── setup.md
│   ├── deployment.md
│   └── troubleshooting.md
├── api/                         # API documentation
│   ├── rest-api.md
│   └── graphql.md
├── diagrams/                    # Architecture diagrams
│   ├── system-context.md
│   ├── container.md
│   └── component.md
└── runbooks/                    # Operational runbooks
    ├── deployment.md
    ├── rollback.md
    └── incident-response.md

ARCHITECTURE.md Template

# Architecture

## Overview
Brief description of the system.

## High-Level Architecture
[Diagram]

## Key Components
### Component 1
**Purpose:** What it does
**Technology:** How it's implemented
**Responsibilities:** What it owns

## Data Flow
1. Customer places order
2. Order service validates
3. Payment processed
4. Inventory updated
5. Confirmation sent

## Technology Stack
- Frontend: Magento 2 + Custom Theme
- Backend: PHP 8.1, Magento 2.4.6
- Database: MySQL 8.0
- Cache: Redis 7.0
- Search: Elasticsearch 7.x
- Queue: RabbitMQ

## Security
- Authentication: JWT tokens
- Authorization: ACL-based
- Data: Encrypted at rest

## Performance
- Target: < 2s page load
- Caching: Redis + Varnish
- CDN: CloudFlare

## Scalability
- Horizontal: Load balancer + multiple app servers
- Database: Read replicas
- Cache: Redis cluster

Living Documentation

Documentation should be:
1. Version controlled (git)
2. Updated with code changes
3. Reviewed in PRs
4. Accessible to all
5. Searchable

Automate:
- API docs from code
- Diagram updates from architecture
- Link checking
- Spell checking

Documentation as Code

Review Process

# .github/workflows/docs.yml
name: Documentation
on:
  pull_request:
    paths: ['docs/**']

jobs:
  lint:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
      - name: Check links
        run: markdown-link-check docs/**/*.md
      - name: Spell check
        run: cspell docs/**/*.md
      - name: Lint markdown
        run: markdownlint docs/**/*.md

Auto-Generation

// Generate API documentation from code
$reader = new DocBlockReader();
$methods = $reader->readClass(\Vendor\Api\ProductInterface::class);

$markdown = "# Product API\n\n";
foreach ($methods as $method) {
    $markdown .= "## {$method->getName()}\n";
    $markdown .= $method->getDescription() . "\n";
    $markdown .= "```php\n{$method->getSignature()}\n```\n\n";
}

file_put_contents('docs/api/product.md', $markdown);

Documentation Metrics

// Track documentation health
$metrics = [
    'total_pages' => count(glob('docs/**/*.md')),
    'outdated_pages' => $this->findOutdated(),
    'broken_links' => $this->checkLinks(),
    'coverage' => $this->calculateCoverage(),
];

// Dashboard
// Documentation Health: 85%
// Outdated Pages: 3
// Broken Links: 0

Maintenance Schedule

Weekly:
- Review new PRs for doc updates
- Check broken links
- Update status reports

Monthly:
- Review outdated content
- Update diagrams
- Archive completed ADRs

Quarterly:
- Architecture review
- Documentation audit
- Team feedback collection

Documentation Debt

Signs of documentation debt:
- New team members take weeks to onboard
- Same questions asked repeatedly
- Documentation contradicts code
- No diagrams for complex systems

Fix documentation debt:
1. Prioritize with feature work
2. Allocate 10% of sprint
3. Boy Scout Rule for docs
4. Auto-generate where possible