[blog-api-server] 모니터링 대시보드 및 알림 시스템 구축

# prometheus_exporter.py
from prometheus_client import Counter, Histogram, Gauge

http_requests_total = Counter(
    'http_requests_total',
    'Total HTTP requests',
    ['method', 'endpoint', 'status']
)

http_request_duration_seconds = Histogram(
    'http_request_duration_seconds',
    'HTTP request latency',
    ['method', 'endpoint']
)

# 미들웨어에서 자동 수집
class PrometheusMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        start_time = time.time()
        response = await call_next(request)
        duration = time.time() - start_time

        http_requests_total.labels(
            method=request.method,
            endpoint=request.url.path,
            status=response.status_code
        ).inc()

        http_request_duration_seconds.labels(
            method=request.method,
            endpoint=request.url.path
        ).observe(duration)

# alerting.py
class AlertManager:
    def check_and_alert(self, metrics: Dict[str, Any]):
        for rule in self.rules:
            if rule.should_trigger(metrics):
                self._send_alert(rule, metrics)

    def _send_alert(self, rule: AlertRule, metrics: Dict[str, Any]):
        message = f"""
Alert Rule: {rule.name}
Condition: {rule.condition}

Current Metrics:
- Total Requests: {metrics.get('total_requests', 0)}
- Error Count: {metrics.get('error_count', 0)}
- Error Rate: {metrics.get('error_rate_percent', 0)}%
- Slow Requests: {metrics.get('slow_request_count', 0)}
"""
        self.slack.send(
            title=f"Alert: {rule.name}",
            message=message.strip(),
            severity=rule.severity
        )

# middleware.py
class MonitoringMiddleware(BaseHTTPMiddleware):
    async def dispatch(self, request: Request, call_next):
        request_id = str(uuid.uuid4())
        start_time = time.time()

        response = await call_next(request)
        process_time = (time.time() - start_time) * 1000

        # 응답 헤더에 추적 정보 추가
        response.headers["X-Process-Time"] = f"{process_time:.2f}"
        response.headers["X-Request-ID"] = request_id

        return response

# Slack 알림
SLACK_WEBHOOK_URL=https://hooks.slack.com/services/...

# Email 알림
SMTP_SERVER=smtp.gmail.com
SMTP_PORT=587
SMTP_USERNAME=your-email@gmail.com
SMTP_PASSWORD=your-app-password
ALERT_FROM_EMAIL=your-email@gmail.com
ALERT_TO_EMAILS=admin@example.com,ops@example.com

# 임계값 설정
SLOW_REQUEST_THRESHOLD=1000  # 1초
VERY_SLOW_THRESHOLD=3000     # 3초
MAX_BODY_LOG_LENGTH=1000