Implement compliance key lifecycle on main service, add message retention and rate limits

backend/services/shared/inter_service_rate_limit.py

@@ -0,0 +1,51 @@
+"""
+Per-IP rate limits for internal FastAPI apps (messaging, file_storage).
+
+Complements the main service's endpoint-specific limits. Uses a generous default
+because traffic is mostly from the main backend (single Docker bridge IP).
+"""
+
+from __future__ import annotations
+
+from fastapi import FastAPI, Request
+from slowapi import Limiter, _rate_limit_exceeded_handler
+from slowapi.errors import RateLimitExceeded
+from slowapi.middleware import SlowAPIMiddleware
+from slowapi.util import get_remote_address
+
+
+def _client_ip_key(request: Request) -> str:
+    if request is None:
+        return "unknown"
+    headers = request.headers
+    real = (headers.get("x-real-ip") or headers.get("X-Real-IP") or "").strip()
+    if real:
+        return real
+    forwarded = headers.get("x-forwarded-for") or headers.get("X-Forwarded-For")
+    if forwarded:
+        first = forwarded.split(",")[0].strip()
+        if first:
+            return first
+    if request.client and request.client.host:
+        return request.client.host
+    return get_remote_address(request)
+
+
+def attach_internal_service_rate_limit(
+    app: FastAPI,
+    *,
+    default_limit: str = "6000/minute",
+) -> Limiter:
+    """
+    Register SlowAPI on ``app`` with a default limit for all routes.
+    Use ``@limiter.exempt`` on ``/health`` (and similar) so probes are not throttled.
+    """
+    limiter = Limiter(
+        key_func=_client_ip_key,
+        default_limits=[default_limit],
+        storage_uri="memory://",
+    )
+    app.state.limiter = limiter
+    app.add_middleware(SlowAPIMiddleware)
+    app.add_exception_handler(RateLimitExceeded, _rate_limit_exceeded_handler)
+    return limiter