feat: queue de téléchargement séquentielle (un à la fois)

asyncio.Queue dans DownloadManager + worker unique démarré dans le lifespan.
Les téléchargements s'exécutent un par un dans l'ordre d'arrivée.
Suppression de BackgroundTasks (plus nécessaire).

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

downloader.py

@@ -8,7 +8,6 @@ from datetime import datetime
 from pathlib import Path
 
 import yt_dlp
-from fastapi import BackgroundTasks
 
 OUTPUT_DIR = "/data/Arte"
 DB_PATH = "data/arte_dl.db"
@@ -87,6 +86,7 @@ class DownloadManager:
     def __init__(self):
         self._active: dict[str, dict] = {}
         self._lock = threading.Lock()
+        self._queue: asyncio.Queue = asyncio.Queue()
         self._init_db()
 
     def _init_db(self):
@@ -147,7 +147,8 @@ class DownloadManager:
             ).fetchone()
         return row is not None
 
-    def _insert_queued(self, url: str, title: str) -> str:
+    async def enqueue(self, url: str, title: str, subtitle: str,
+                      year: int | None, category: str) -> str:
         dl_id = str(uuid.uuid4())
         now = datetime.now().isoformat()
         with _db() as conn:
@@ -157,20 +158,15 @@ class DownloadManager:
             )
         with self._lock:
             self._active[dl_id] = {"state": "queued", "progress": 0, "title": title}
+        await self._queue.put((dl_id, url, title, subtitle, year, category))
         return dl_id
 
-    def enqueue(self, url: str, title: str, subtitle: str, year: int | None,
-                category: str, bg: BackgroundTasks) -> str:
-        dl_id = self._insert_queued(url, title)
-        bg.add_task(self._run, dl_id, url, title, subtitle, year, category)
-        return dl_id
-
-    async def enqueue_direct(self, url: str, title: str, subtitle: str,
-                             year: int | None, category: str) -> str:
-        dl_id = self._insert_queued(url, title)
+    async def start_worker(self):
         loop = asyncio.get_running_loop()
-        loop.run_in_executor(None, self._run, dl_id, url, title, subtitle, year, category)
-        return dl_id
+        while True:
+            job = await self._queue.get()
+            dl_id, url, title, subtitle, year, category = job
+            await loop.run_in_executor(None, self._run, dl_id, url, title, subtitle, year, category)
 
     def status(self, dl_id: str) -> dict:
         with self._lock:
@@ -183,13 +179,6 @@ class DownloadManager:
             ).fetchall()
         return [dict(r) for r in rows]
 
-    def already_downloaded(self, url: str) -> bool:
-        with _db() as conn:
-            row = conn.execute(
-                "SELECT id FROM downloads WHERE url=? AND state='done' LIMIT 1", (url,)
-            ).fetchone()
-        return row is not None
-
     # ----------------------------------------------------------------- private
 
     def _set(self, dl_id: str, **kw):

main.py

@@ -5,7 +5,7 @@ import os
 import re
 from contextlib import asynccontextmanager
 
-from fastapi import BackgroundTasks, FastAPI, HTTPException, Request
+from fastapi import FastAPI, HTTPException, Request
 from fastapi.responses import HTMLResponse, StreamingResponse
 from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
@@ -52,13 +52,14 @@ async def _auto_dl_loop():
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
-    task = asyncio.create_task(_auto_dl_loop())
+    tasks = [
+        asyncio.create_task(dm.start_worker()),
+        asyncio.create_task(_auto_dl_loop()),
+    ]
     yield
-    task.cancel()
-    try:
-        await task
-    except asyncio.CancelledError:
-        pass
+    for t in tasks:
+        t.cancel()
+    await asyncio.gather(*tasks, return_exceptions=True)
 
 
 app = FastAPI(title="Arte-dl", lifespan=lifespan)
@@ -133,10 +134,10 @@ class DownloadRequest(BaseModel):
 
 
 @app.post("/api/download")
-async def api_download(req: DownloadRequest, bg: BackgroundTasks):
+async def api_download(req: DownloadRequest):
     if not req.url:
         raise HTTPException(status_code=400, detail="url required")
-    dl_id = dm.enqueue(req.url, req.title, req.subtitle, req.year, req.category, bg)
+    dl_id = await dm.enqueue(req.url, req.title, req.subtitle, req.year, req.category)
     return {"id": dl_id}