fix(network): improve torrent fetch reliability and error handling

- Add browser-like headers and full Chrome User-Agent to avoid Cloudflare blocking
- Use appropriate Accept headers for torrent files (application/x-bittorrent)
- Increase timeouts (connect: 5s→10s, read: 10s→30s) for slow responses
- Filter out None values from failed torrent fetches before sending to qBittorrent
- Add try-catch around add_torrents to prevent request crashes
- Improve logging from DEBUG to WARNING level for better visibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/src/module/downloader/download_client.py

@@ -31,6 +31,11 @@ class DownloadClient(TorrentPath):
             from .client.aria2_downloader import Aria2Downloader
 
             return Aria2Downloader(host, username, password)
+        elif type == "mock":
+            from .client.mock_downloader import MockDownloader
+
+            logger.info("[Downloader] Using MockDownloader for local development")
+            return MockDownloader()
         else:
             logger.error(f"[Downloader] Unsupported downloader type: {type}")
             raise Exception(f"Unsupported downloader type: {type}")
@@ -141,6 +146,11 @@ class DownloadClient(TorrentPath):
                     torrent_file = await asyncio.gather(
                         *[req.get_content(t.url) for t in torrent]
                     )
+                    # Filter out None values (failed fetches)
+                    torrent_file = [f for f in torrent_file if f is not None]
+                    if not torrent_file:
+                        logger.warning(f"[Downloader] Failed to fetch torrent files for: {bangumi.official_title}")
+                        return False
                     torrent_url = None
             else:
                 if "magnet" in torrent.url:
@@ -148,17 +158,24 @@ class DownloadClient(TorrentPath):
                     torrent_file = None
                 else:
                     torrent_file = await req.get_content(torrent.url)
+                    if torrent_file is None:
+                        logger.warning(f"[Downloader] Failed to fetch torrent file for: {bangumi.official_title}")
+                        return False
                     torrent_url = None
-        if await self.client.add_torrents(
-            torrent_urls=torrent_url,
-            torrent_files=torrent_file,
-            save_path=bangumi.save_path,
-            category="Bangumi",
-        ):
-            logger.debug(f"[Downloader] Add torrent: {bangumi.official_title}")
-            return True
-        else:
-            logger.debug(f"[Downloader] Torrent added before: {bangumi.official_title}")
+        try:
+            if await self.client.add_torrents(
+                torrent_urls=torrent_url,
+                torrent_files=torrent_file,
+                save_path=bangumi.save_path,
+                category="Bangumi",
+            ):
+                logger.debug(f"[Downloader] Add torrent: {bangumi.official_title}")
+                return True
+            else:
+                logger.debug(f"[Downloader] Torrent added before: {bangumi.official_title}")
+                return False
+        except Exception as e:
+            logger.error(f"[Downloader] Failed to add torrent for {bangumi.official_title}: {e}")
             return False
 
     async def move_torrent(self, hashes, location):

backend/src/module/network/request_contents.py

@@ -67,6 +67,8 @@ class RequestContent(RequestURL):
         req = await self.get_url(_url)
         if req:
             return req.content
+        logger.warning(f"[Network] Failed to get content from {_url}")
+        return None
 
     async def check_connection(self, _url):
         return await self.check_url(_url)

backend/src/module/network/request_url.py

@@ -26,7 +26,7 @@ async def get_shared_client() -> httpx.AsyncClient:
         return _shared_client
     if _shared_client is not None:
         await _shared_client.aclose()
-    timeout = httpx.Timeout(connect=5.0, read=10.0, write=10.0, pool=10.0)
+    timeout = httpx.Timeout(connect=10.0, read=30.0, write=10.0, pool=10.0)
     if settings.proxy.enable:
         if "http" in settings.proxy.type:
             if settings.proxy.username:
@@ -50,31 +50,50 @@ async def get_shared_client() -> httpx.AsyncClient:
 
 
 class RequestURL:
+    # More complete User-Agent to avoid Cloudflare blocking
+    DEFAULT_UA = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36"
+
     def __init__(self):
-        self.header = {"user-agent": "Mozilla/5.0", "Accept": "application/xml"}
+        self.header = {"User-Agent": self.DEFAULT_UA, "Accept": "application/xml"}
         self._client: httpx.AsyncClient | None = None
 
+    def _get_headers(self, url: str) -> dict:
+        """Get appropriate headers based on URL type."""
+        base_headers = {
+            "User-Agent": self.DEFAULT_UA,
+            "Accept-Language": "en-US,en;q=0.9",
+            "Accept-Encoding": "gzip, deflate, br",
+            "Connection": "keep-alive",
+        }
+        # For torrent files, use different Accept header
+        if url.endswith(".torrent") or "/download/" in url:
+            base_headers["Accept"] = "application/x-bittorrent, application/octet-stream, */*"
+        else:
+            base_headers["Accept"] = "application/xml, text/xml, */*"
+        return base_headers
+
     async def get_url(self, url, retry=3):
         try_time = 0
+        headers = self._get_headers(url)
         while True:
             try:
-                req = await self._client.get(url=url, headers=self.header)
+                req = await self._client.get(url=url, headers=headers)
                 logger.debug(f"[Network] Successfully connected to {url}. Status: {req.status_code}")
                 req.raise_for_status()
                 return req
-            except httpx.HTTPStatusError:
-                logger.debug(f"[Network] HTTP error from {url}.")
+            except httpx.HTTPStatusError as e:
+                logger.warning(f"[Network] HTTP {e.response.status_code} from {url}")
                 break
-            except httpx.RequestError:
-                logger.debug(
-                    f"[Network] Cannot connect to {url}. Wait for 5 seconds."
+            except httpx.RequestError as e:
+                logger.warning(
+                    f"[Network] Request error for {url}: {type(e).__name__}. Retry {try_time + 1}/{retry}"
                 )
                 try_time += 1
                 if try_time >= retry:
                     break
                 await asyncio.sleep(5)
             except Exception as e:
-                logger.debug(e)
+                logger.warning(f"[Network] Unexpected error for {url}: {e}")
                 break
         logger.error(f"[Network] Unable to connect to {url}, Please check your network settings")
         return None