WebApp changes

src/MangaBakaRateLimit.py

@@ -0,0 +1,92 @@
+"""
+mangabaka_rate_limit.py
+=======================
+
+Process-wide rate limiter for the MangaBaka API.
+
+Apply via:
+
+    from MangaBakaRateLimit import apply_to_session
+    apply_to_session(session)
+
+This mounts a custom ``requests.adapters.HTTPAdapter`` on the given
+``requests.Session`` for the ``api.mangabaka.dev`` host.  Every request
+going through that adapter is:
+
+  * throttled so that no two requests are dispatched within
+    ``_MIN_INTERVAL`` seconds of one another, and
+  * retried on HTTP 429, honouring the ``Retry-After`` header when
+    present, otherwise exponential backoff capped at ``_MAX_BACKOFF``.
+
+Throttle state is module-global, so even if several sessions exist in
+the same process they share one budget — important because they all hit
+the same upstream IP-based limit.
+"""
+
+from __future__ import annotations
+
+import threading
+import time
+
+from requests.adapters import HTTPAdapter
+
+
+# Tune these if MangaBaka tightens or loosens limits.
+_MIN_INTERVAL = 1.1      # seconds between consecutive requests
+_MAX_RETRIES  = 6        # retries on 429 before giving up
+_MAX_BACKOFF  = 60.0     # cap on per-attempt backoff sleep
+
+
+# --- shared throttle state --------------------------------------------------
+_state_lock        = threading.Lock()
+_last_request_time = 0.0
+
+
+def _wait_for_slot() -> None:
+    """Block until the next request slot is available, then reserve it."""
+    global _last_request_time
+    while True:
+        with _state_lock:
+            now  = time.monotonic()
+            wait = _MIN_INTERVAL - (now - _last_request_time)
+            if wait <= 0:
+                _last_request_time = now
+                return
+        time.sleep(wait)
+
+
+class _MangaBakaRateLimitAdapter(HTTPAdapter):
+    def send(self, request, **kwargs):
+        response = None
+        for attempt in range(_MAX_RETRIES + 1):
+            _wait_for_slot()
+            response = super().send(request, **kwargs)
+            if response.status_code != 429:
+                return response
+
+            retry_after = response.headers.get("Retry-After")
+            try:
+                wait = (float(retry_after) if retry_after
+                        else min(_MAX_BACKOFF, 2.0 * (2 ** attempt)))
+            except ValueError:
+                wait = min(_MAX_BACKOFF, 2.0 * (2 ** attempt))
+
+            print(f"[MangaBaka] 429 — backing off {wait:.1f}s "
+                  f"(attempt {attempt + 1}/{_MAX_RETRIES})",
+                  flush=True)
+            response.close()
+            time.sleep(wait)
+
+        # Retries exhausted — let the caller deal with the last 429.
+        return response
+
+
+def apply_to_session(session) -> None:
+    """
+    Mount the rate-limit adapter on ``session`` so every MangaBaka call
+    is automatically throttled. Safe to call multiple times (later mounts
+    just replace the earlier adapter for the same prefix).
+    """
+    adapter = _MangaBakaRateLimitAdapter()
+    session.mount("https://api.mangabaka.dev/", adapter)
+    session.mount("http://api.mangabaka.dev/",  adapter)