# Backend Performance & Production Features - Implementation Summary

## Overview

This document summarizes the implementation of 5 backend tasks for mockupAWS v1.0.0 production release.

---

## BE-PERF-004: Redis Caching Layer ✅

### Implementation Files
- `src/core/cache.py` - Cache manager with multi-level caching
- `redis.conf` - Redis server configuration

### Features
1. **Redis Setup**
   - Connection pooling (max 50 connections)
   - Automatic reconnection with health checks
   - Persistence configuration (RDB snapshots)
   - Memory management (512MB max, LRU eviction)

2. **Three-Level Caching Strategy**
   - **L1 Cache** (5 min TTL): DB query results (scenario list, metrics)
   - **L2 Cache** (1 hour TTL): Report generation (PDF cache)
   - **L3 Cache** (24 hours TTL): AWS pricing data

3. **Implementation Features**
   - `@cached(ttl=300)` decorator for easy caching
   - Automatic cache key generation (SHA256 hash)
   - Cache warming support with distributed locking
   - Cache invalidation by pattern
   - Statistics endpoint for monitoring

### Usage Example
```python
from src.core.cache import cached, cache_manager

@cached(ttl=300)
async def get_scenario_list():
    # This result will be cached for 5 minutes
    return await scenario_repository.get_multi(db)

# Manual cache operations
await cache_manager.set_l1("scenarios", data)
cached_data = await cache_manager.get_l1("scenarios")
```

---

## BE-PERF-005: Async Optimization ✅

### Implementation Files
- `src/core/celery_app.py` - Celery configuration
- `src/tasks/reports.py` - Async report generation
- `src/tasks/emails.py` - Async email sending
- `src/tasks/cleanup.py` - Scheduled cleanup tasks
- `src/tasks/pricing.py` - AWS pricing updates
- `src/tasks/__init__.py` - Task exports

### Features
1. **Celery Configuration**
   - Redis broker and result backend
   - Separate queues: default, reports, emails, cleanup, priority
   - Task routing by type
   - Rate limiting (10 reports/minute, 100 emails/minute)
   - Automatic retry with exponential backoff
   - Task timeout protection (5 minutes)

2. **Background Jobs**
   - **Report Generation**: PDF/CSV generation moved to async workers
   - **Email Sending**: Welcome, password reset, report ready notifications
   - **Cleanup Jobs**: Old reports, expired sessions, stale cache
   - **Pricing Updates**: Daily AWS pricing refresh with cache warming

3. **Scheduled Tasks (Celery Beat)**
   - Cleanup old reports: Every 6 hours
   - Cleanup expired sessions: Every hour
   - Update AWS pricing: Daily
   - Health check: Every minute

4. **Monitoring Integration**
   - Task start/completion/failure metrics
   - Automatic error logging with correlation IDs
   - Task duration tracking

### Docker Services
- `celery-worker`: Processes background tasks
- `celery-beat`: Task scheduler
- `flower`: Web UI for monitoring (port 5555)

### Usage Example
```python
from src.tasks.reports import generate_pdf_report

# Queue a report generation task
task = generate_pdf_report.delay(
    scenario_id="uuid",
    report_id="uuid",
    include_sections=["summary", "costs"]
)

# Check task status
result = task.get(timeout=300)
```

---

## BE-API-006: API Versioning & Documentation ✅

### Implementation Files
- `src/api/v2/__init__.py` - API v2 router
- `src/api/v2/rate_limiter.py` - Tiered rate limiting
- `src/api/v2/endpoints/scenarios.py` - Enhanced scenarios API
- `src/api/v2/endpoints/reports.py` - Async reports API
- `src/api/v2/endpoints/metrics.py` - Cached metrics API
- `src/api/v2/endpoints/auth.py` - Enhanced auth API
- `src/api/v2/endpoints/health.py` - Health & monitoring endpoints
- `src/api/v2/endpoints/__init__.py`

### Features

1. **API Versioning**
   - `/api/v1/` - Original API (backward compatible)
   - `/api/v2/` - New enhanced API
   - Deprecation headers for v1 endpoints
   - Migration guide endpoint at `/api/deprecation`

2. **Rate Limiting (Tiered)**
   - **Free Tier**: 100 requests/minute, burst 10
   - **Premium Tier**: 1000 requests/minute, burst 50
   - **Enterprise Tier**: 10000 requests/minute, burst 200
   - Per-API-key tracking
   - Rate limit headers (X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset)

3. **Enhanced Endpoints**
   - **Scenarios**: Bulk operations, search, improved filtering
   - **Reports**: Async generation with Celery, status polling
   - **Metrics**: Force refresh option, lightweight summary endpoint
   - **Auth**: Enhanced error handling, audit logging

4. **OpenAPI Documentation**
   - All endpoints documented with summaries and descriptions
   - Response examples and error codes
   - Authentication flows documented
   - Rate limit information included

### Rate Limit Headers Example
```http
X-RateLimit-Limit: 100
X-RateLimit-Remaining: 95
X-RateLimit-Reset: 1704067200
```

---

## BE-MON-007: Monitoring & Observability ✅

### Implementation Files
- `src/core/monitoring.py` - Prometheus metrics
- `src/core/logging_config.py` - Structured JSON logging
- `src/core/tracing.py` - OpenTelemetry tracing

### Features

1. **Application Monitoring (Prometheus)**
   - HTTP metrics: requests total, duration, size
   - Database metrics: queries total, duration, connections
   - Cache metrics: hits, misses by level
   - Business metrics: scenarios, reports, users
   - Celery metrics: tasks started, completed, failed
   - Custom metrics endpoint at `/api/v2/health/metrics`

2. **Structured JSON Logging**
   - JSON formatted logs with correlation IDs
   - Log levels: DEBUG, INFO, WARNING, ERROR
   - Context variables for request tracking
   - Security event logging
   - Centralized logging ready (ELK/Loki compatible)

3. **Distributed Tracing (OpenTelemetry)**
   - Jaeger exporter support
   - OTLP exporter support
   - Automatic FastAPI instrumentation
   - Database query tracing
   - Redis operation tracing
   - Celery task tracing
   - Custom span decorators

4. **Health Checks**
   - `/health` - Basic health check
   - `/api/v2/health/live` - Kubernetes liveness probe
   - `/api/v2/health/ready` - Kubernetes readiness probe
   - `/api/v2/health/startup` - Kubernetes startup probe
   - `/api/v2/health/metrics` - Prometheus metrics
   - `/api/v2/health/info` - Application info

### Metrics Example
```python
from src.core.monitoring import metrics, track_db_query

# Track custom counter
metrics.increment_counter("custom_event", labels={"type": "example"})

# Track database query
track_db_query("SELECT", "users", duration_seconds)

# Use timer context manager
with metrics.timer("operation_duration", labels={"name": "process_data"}):
    process_data()
```

---

## BE-SEC-008: Security Hardening ✅

### Implementation Files
- `src/core/security_headers.py` - Security headers middleware
- `src/core/audit_logger.py` - Audit logging system

### Features

1. **Security Headers**
   - HSTS (Strict-Transport-Security): 1 year max-age
   - CSP (Content-Security-Policy): Strict policy per context
   - X-Frame-Options: DENY
   - X-Content-Type-Options: nosniff
   - Referrer-Policy: strict-origin-when-cross-origin
   - Permissions-Policy: Restricted feature access
   - X-XSS-Protection: 1; mode=block
   - Cache-Control: no-store for sensitive data

2. **CORS Configuration**
   - Strict origin validation
   - Allowed methods: GET, POST, PUT, DELETE, PATCH, OPTIONS
   - Custom headers: Authorization, X-API-Key, X-Correlation-ID
   - Exposed headers: Rate limit information
   - Environment-specific origin lists

3. **Input Validation**
   - String length limits (10KB max)
   - XSS pattern detection
   - HTML sanitization helpers
   - JSON size limits (1MB max)

4. **Audit Logging**
   - Immutable audit log entries with integrity hash
   - Event types: auth, API keys, scenarios, reports, admin
   - 1 year retention policy
   - Security event detection
   - Compliance-ready format

5. **Audit Events Tracked**
   - Login success/failure
   - Password changes
   - API key creation/revocation
   - Scenario CRUD operations
   - Report generation/download
   - Suspicious activity

### Audit Log Example
```python
from src.core.audit_logger import audit_logger, AuditEventType

# Log custom event
audit_logger.log(
    event_type=AuditEventType.SCENARIO_CREATED,
    action="create_scenario",
    user_id=user_uuid,
    resource_type="scenario",
    resource_id=scenario_uuid,
    details={"name": scenario_name},
)
```

---

## Docker Compose Updates

### New Services

1. **Redis** (`redis:7-alpine`)
   - Port: 6379
   - Persistence enabled
   - Memory limit: 512MB
   - Health checks enabled

2. **Celery Worker**
   - Processes background tasks
   - Concurrency: 4 workers
   - Auto-restart on failure

3. **Celery Beat**
   - Task scheduler
   - Persistent schedule storage

4. **Flower**
   - Web UI for Celery monitoring
   - Port: 5555
   - Real-time task monitoring

5. **Backend** (Updated)
   - Health checks enabled
   - Log volumes mounted
   - Environment variables for all features

---

## Configuration Updates

### New Environment Variables

```bash
# Application
APP_VERSION=1.0.0
LOG_LEVEL=INFO
JSON_LOGGING=true

# Redis
REDIS_URL=redis://localhost:6379/0
CACHE_DISABLED=false

# Celery
CELERY_BROKER_URL=redis://localhost:6379/1
CELERY_RESULT_BACKEND=redis://localhost:6379/2

# Security
CORS_ALLOWED_ORIGINS=["http://localhost:3000"]
AUDIT_LOGGING_ENABLED=true

# Tracing
JAEGER_ENDPOINT=localhost
JAEGER_PORT=6831
OTLP_ENDPOINT=

# Email
SMTP_HOST=localhost
SMTP_PORT=587
SMTP_USER=
SMTP_PASSWORD=
DEFAULT_FROM_EMAIL=noreply@mockupaws.com
```

---

## Dependencies Added

### Caching & Queue
- `redis==5.0.3`
- `hiredis==2.3.2`
- `celery==5.3.6`
- `flower==2.0.1`

### Monitoring
- `prometheus-client==0.20.0`
- `opentelemetry-api==1.24.0`
- `opentelemetry-sdk==1.24.0`
- `opentelemetry-instrumentation-*`
- `python-json-logger==2.0.7`

### Security & Validation
- `slowapi==0.1.9`
- `email-validator==2.1.1`
- `pydantic-settings==2.2.1`

---

## Testing & Verification

### Health Check Endpoints
- `GET /health` - Application health
- `GET /api/v2/health/ready` - Database & cache connectivity
- `GET /api/v2/health/metrics` - Prometheus metrics

### Celery Monitoring
- Flower UI: http://localhost:5555/flower/
- Task status via API: `GET /api/v2/reports/{id}/status`

### Cache Testing
```python
# Test cache connectivity
from src.core.cache import cache_manager
await cache_manager.initialize()
stats = await cache_manager.get_stats()
print(stats)
```

---

## Migration Guide

### For API Clients

1. **Update API Version**
   - Change base URL from `/api/v1/` to `/api/v2/`
   - v1 will be deprecated on 2026-12-31

2. **Handle Rate Limits**
   - Check `X-RateLimit-Remaining` header
   - Implement retry with exponential backoff on 429

3. **Async Reports**
   - POST to create report → returns task ID
   - Poll GET status endpoint until complete
   - Download when status is "completed"

4. **Correlation IDs**
   - Send `X-Correlation-ID` header for request tracing
   - Check response headers for tracking

### For Developers

1. **Start Services**
   ```bash
   docker-compose up -d redis celery-worker celery-beat
   ```

2. **Monitor Tasks**
   ```bash
   # Open Flower UI
   open http://localhost:5555/flower/
   ```

3. **Check Logs**
   ```bash
   # View structured JSON logs
   docker-compose logs -f backend
   ```

---

## Summary

All 5 backend tasks have been successfully implemented:

✅ **BE-PERF-004**: Redis caching layer with 3-level strategy  
✅ **BE-PERF-005**: Celery async workers for background jobs  
✅ **BE-API-006**: API v2 with versioning and rate limiting  
✅ **BE-MON-007**: Prometheus metrics, JSON logging, tracing  
✅ **BE-SEC-008**: Security headers, audit logging, input validation  

The system is now production-ready with:
- Horizontal scaling support (multiple workers)
- Comprehensive monitoring and alerting
- Security hardening and audit compliance
- API versioning for backward compatibility
