| """ |
| services/rate_limiter.py |
| ──────────────────────── |
| In-memory session rate limiter enforcing minute and daily rate limits. |
| """ |
|
|
| import time |
| from collections import defaultdict |
| from fastapi import HTTPException |
|
|
|
|
| def _is_idle_session(times: list, cutoff: float) -> bool: |
| """Returns True if the request timestamps indicate idle session beyond cutoff.""" |
| return not times or max(times) < cutoff |
|
|
|
|
| class SessionRateLimiter: |
| """Tracks per-session requests against RPM and daily quotas.""" |
|
|
| def __init__(self, requests_per_minute: int = 10, max_daily: int = 50): |
| self.rpm = requests_per_minute |
| self.max_daily = max_daily |
| self.requests = defaultdict(list) |
| self.daily_counts = defaultdict(lambda: {"count": 0, "reset_at": 0}) |
|
|
| def evict_stale(self, max_idle_seconds: int = 90_000) -> None: |
| """Evicts sessions idle for longer than max_idle_seconds to prevent memory leaks.""" |
| cutoff = time.time() - max_idle_seconds |
| stale_req = [sid for sid, times in self.requests.items() if _is_idle_session(times, cutoff)] |
| stale_daily = [sid for sid, data in self.daily_counts.items() if data["reset_at"] < cutoff] |
| for sid in stale_req: |
| del self.requests[sid] |
| for sid in stale_daily: |
| del self.daily_counts[sid] |
|
|
| def _check_daily_limit(self, client_id: str, now: float): |
| """Verifies and updates the daily 24-hour request quota.""" |
| daily = self.daily_counts[client_id] |
| if now > daily["reset_at"]: |
| daily["count"] = 0 |
| daily["reset_at"] = now + 86400 |
|
|
| if daily["count"] >= self.max_daily: |
| raise HTTPException( |
| status_code=429, |
| detail="Daily limit of 50 messages reached for this session." |
| ) |
|
|
| def _check_rpm_limit(self, client_id: str, now: float): |
| """Verifies and updates the rolling 60-second window quota.""" |
| window = [t for t in self.requests[client_id] if now - t < 60] |
| self.requests[client_id] = window |
|
|
| if len(window) >= self.rpm: |
| raise HTTPException( |
| status_code=429, |
| detail="Rate limit exceeded. Please wait 1 minute before sending another question." |
| ) |
|
|
| def check_rate_limit(self, client_id: str): |
| """Validates incoming request against session eviction, daily, and RPM limits.""" |
| now = time.time() |
| self.evict_stale() |
| self._check_daily_limit(client_id, now) |
| self._check_rpm_limit(client_id, now) |
|
|
| self.requests[client_id].append(now) |
| self.daily_counts[client_id]["count"] += 1 |
|
|
|
|
| limiter = SessionRateLimiter() |
|
|
