posthog-reference-architecture

# PostHog Reference Architecture ## Overview Production-ready architecture patterns for PostHog integrations. ## Prerequisites - Understanding of layered architecture - PostHog SDK knowledge - TypeScript project setup - Testing framework configured ## Project Structure ``` my-posthog-project/ ├── src/ │ ├── posthog/ │ │ ├── client.ts # Singleton client wrapper │ │ ├── config.ts # Environment configuration │ │ ├── types.ts # TypeScript types │ │ ├── errors.ts # Custom error classes │ │ └── handlers/ │ │ ├── webhooks.ts # Webhook handlers │ │ └── events.ts # Event processing │ ├── services/ │ │ └── posthog/ │ │ ├── index.ts # Service facade │ │ ├── sync.ts # Data synchronization │ │ └── cache.ts # Caching layer │ ├── api/ │ │ └── posthog/ │ │ └── webhook.ts # Webhook endpoint │ └── jobs/ │ └── posthog/ │ └── sync.ts # Background sync job ├── tests/ │ ├── unit/ │ │ └── posthog/ │ └── integration/ │ └── posthog/ ├── config/ │ ├── posthog.development.json │ ├── posthog.staging.json │ └── posthog.production.json └── docs/ └── posthog/ ├── SETUP.md └── RUNBOOK.md ``` ## Layer Architecture ``` ┌─────────────────────────────────────────┐ │ API Layer │ │ (Controllers, Routes, Webhooks) │ ├─────────────────────────────────────────┤ │ Service Layer │ │ (Business Logic, Orchestration) │ ├─────────────────────────────────────────┤ │ PostHog Layer │ │ (Client, Types, Error Handling) │ ├─────────────────────────────────────────┤ │ Infrastructure Layer │ │ (Cache, Queue, Monitoring) │ └─────────────────────────────────────────┘ ``` ## Key Components ### Step 1: Client Wrapper ```typescript // src/posthog/client.ts export class PostHogService { private client: PostHogClient; private cache: Cache; private monitor: Monitor; constructor(config: PostHogConfig) { this.client = new PostHogClient(config); this.cache = new Cache(config.cacheOptions); this.monitor = new Monitor('posthog'); } async get(id: string): Promise { return this.cache.getOrFetch(id, () => this.monitor.track('get', () => this.client.get(id)) ); } } ``` ### Step 2: Error Boundary ```typescript // src/posthog/errors.ts export class PostHogServiceError extends Error { constructor( message: string, public readonly code: string, public readonly retryable: boolean, public readonly originalError?: Error ) { super(message); this.name = 'PostHogServiceError'; } } export function wrapPostHogError(error: unknown): PostHogServiceError { // Transform SDK errors to application errors } ``` ### Step 3: Health Check ```typescript // src/posthog/health.ts export async function checkPostHogHealth(): Promise { try { const start = Date.now(); await posthogClient.ping(); return { status: 'healthy', latencyMs: Date.now() - start, }; } catch (error) { return { status: 'unhealthy', error: error.message }; } } ``` ## Data Flow Diagram ``` User Request │ ▼ ┌─────────────┐ │ API │ │ Gateway │ └──────┬──────┘ │ ▼ ┌─────────────┐ ┌─────────────┐ │ Service │───▶│ Cache │ │ Layer │ │ (Redis) │ └──────┬──────┘ └─────────────┘ │ ▼ ┌─────────────┐ │ PostHog │ │ Client │ └──────┬──────┘ │ ▼ ┌─────────────┐ │ PostHog │ │ API │ └─────────────┘ ``` ## Configuration Management ```typescript // config/posthog.ts export interface PostHogConfig { apiKey: string; environment: 'development' | 'staging' | 'production'; timeout: number; retries: number; cache: { enabled: boolean; ttlSeconds: number; }; } export function loadPostHogConfig(): PostHogConfig { const env = process.env.NODE_ENV || 'development'; return require(`./posthog.${env}.json`); } ``` ## Instructions ### Step 1: Create Directory Structure Set up the project layout following the reference structure above. ### Step 2: Implement Client Wrapper Create the singleton client with caching and monitoring. ### Step 3: Add Error Handling Implement custom error classes for PostHog operations. ### Step 4: Configure Health Checks Add health check endpoint for PostHog connectivity. ## Output - Structured project layout - Client wrapper with caching - Error boundary implemented - Health checks configured ## Error Handling | Issue | Cause | Solution | |-------|-------|----------| | Circular dependencies | Wrong layering | Separate concerns by layer | | Config not loading | Wrong paths | Verify config file locations | | Type errors | Missing types | Add PostHog types | | Test isolation | Shared state | Use dependency injection | ## Examples ### Quick Setup Script ```bash # Create reference structure mkdir -p src/posthog/{handlers} src/services/posthog src/api/posthog touch src/posthog/{client,config,types,errors}.ts touch src/services/posthog/{index,sync,cache}.ts ``` ## Resources - [PostHog SDK Documentation](https://docs.posthog.com/sdk) - [PostHog Best Practices](https://docs.posthog.com/best-practices) ## Flagship Skills For multi-environment setup, see `posthog-multi-env-setup`.