Rate limit only background batch fetches, not user requests

fetch_video_metadata and fetch_channel_metadata now take polite=True for
background tasks (enforces 5s+ gap via global lock) while user-facing
calls (watch page, follow channel, download) use polite=False and run
immediately.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/routers/channels.py

@@ -92,7 +92,7 @@ def _index_channel_task(channel_id: int, user_id: int, max_videos: int = 30):
         if not channel:
             return
 
-        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=max_videos)
+        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=max_videos, polite=True)
         if not result:
             return
 
@@ -206,7 +206,7 @@ def _enrich_missing_task(limit: int = 20):
         ).mappings().all()
         for row in rows:
             try:
-                meta = ytdlp.fetch_video_metadata(row["youtube_video_id"])
+                meta = ytdlp.fetch_video_metadata(row["youtube_video_id"], polite=True)
                 if meta:
                     vid = db.query(Video).filter_by(id=row["id"]).first()
                     if vid:
@@ -820,7 +820,7 @@ def _fetch_popular_task(channel_id: int, youtube_channel_id: str, channel_name:
     try:
         for yt_id in video_ids:
             try:
-                meta = ytdlp.fetch_video_metadata(yt_id)
+                meta = ytdlp.fetch_video_metadata(yt_id, polite=True)
                 if meta:
                     db = SessionLocal()
                     try:
@@ -866,7 +866,7 @@ def _search_channel_task(channel_id: int, youtube_channel_id: str, q: str, user_
     db = SessionLocal()
     try:
         url = f"https://www.youtube.com/channel/{youtube_channel_id}/search?query={quote(q)}"
-        result = ytdlp.fetch_channel_metadata(youtube_channel_id, max_videos=100)
+        result = ytdlp.fetch_channel_metadata(youtube_channel_id, max_videos=100, polite=True)
         if not result:
             return
         # Filter results by query match (yt-dlp fetches all; we filter titles locally)
@@ -1050,7 +1050,7 @@ def _index_channel_explore_task(channel_id: int, user_id: int, start_video: int,
         channel = db.query(Channel).filter_by(id=channel_id).first()
         if not channel:
             return
-        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=count, start_video=start_video)
+        result = ytdlp.fetch_channel_metadata(channel.youtube_channel_id, max_videos=count, start_video=start_video, polite=True)
         if not result:
             return
         for vdata in result.get("videos", []):

backend/services/ytdlp.py

@@ -244,8 +244,12 @@ def _best_thumbnail(thumbnails: list | None) -> str | None:
     return best[0].get("url") if best else None
 
 
-def fetch_video_metadata(video_id: str) -> dict | None:
-    """Fetch metadata for a single video by YouTube ID."""
+def fetch_video_metadata(video_id: str, polite: bool = False) -> dict | None:
+    """Fetch metadata for a single video by YouTube ID.
+
+    polite=True applies the global rate limiter (for background batch tasks).
+    polite=False (default) runs immediately for user-facing requests.
+    """
     url = f"https://www.youtube.com/watch?v={video_id}"
     cookie_args = _cookie_args()
     print(f"[fetch_meta] video={video_id} cookie_args={cookie_args!r}", flush=True)
@@ -253,13 +257,13 @@ def fetch_video_metadata(video_id: str) -> dict | None:
         "yt-dlp", url,
         "--dump-json", "--no-download", "--no-playlist",
     ]
-    stdout, stderr, code = _meta_run([*base_cmd, *cookie_args], timeout=30)
+    runner = _meta_run if polite else _run
+    stdout, stderr, code = runner([*base_cmd, *cookie_args], timeout=30)
     if code != 0:
         print(f"[fetch_meta] FAILED code={code} stderr={stderr[:500]!r}", flush=True)
-        # Retry without auth args — broken cookie config shouldn't block public videos
         if cookie_args:
             print(f"[fetch_meta] retrying without cookie args", flush=True)
-            stdout, stderr, code = _meta_run(base_cmd, timeout=30)
+            stdout, stderr, code = runner(base_cmd, timeout=30)
             if code != 0:
                 print(f"[fetch_meta] retry also FAILED code={code}", flush=True)
 
@@ -307,7 +311,7 @@ def _rss_dates(uc_channel_id: str) -> dict[str, datetime]:
         return {}
 
 
-def fetch_channel_metadata(channel_id: str, max_videos: int = 30, start_video: int = 1) -> dict | None:
+def fetch_channel_metadata(channel_id: str, max_videos: int = 30, start_video: int = 1, polite: bool = False) -> dict | None:
     """Fetch channel info + recent videos.
 
     Uses --dump-single-json --flat-playlist for speed, then enriches video dates
@@ -330,7 +334,8 @@ def fetch_channel_metadata(channel_id: str, max_videos: int = 30, start_video: i
         end = (start_video - 1 + max_videos) if start_video > 1 else max_videos
         args += ["--playlist-end", str(end)]
 
-    stdout, _, code = _meta_run(args, timeout=60)
+    runner = _meta_run if polite else _run
+    stdout, _, code = runner(args, timeout=60)
     if not stdout.strip():
         return None