fix(download): recover stalled transfers automatically

py/services/download_manager.py

@@ -15,7 +15,7 @@ from ..utils.metadata_manager import MetadataManager
 from .service_registry import ServiceRegistry
 from .settings_manager import get_settings_manager
 from .metadata_service import get_default_metadata_provider
-from .downloader import get_downloader, DownloadProgress
+from .downloader import get_downloader, DownloadProgress, DownloadStreamControl
 
 # Download to temporary file first
 import tempfile
@@ -44,7 +44,7 @@ class DownloadManager:
         self._active_downloads = OrderedDict()  # download_id -> download_info
         self._download_semaphore = asyncio.Semaphore(5)  # Limit concurrent downloads
         self._download_tasks = {}  # download_id -> asyncio.Task
-        self._pause_events: Dict[str, asyncio.Event] = {}
+        self._pause_events: Dict[str, DownloadStreamControl] = {}
     
     async def _get_lora_scanner(self):
         """Get the lora scanner from registry"""
@@ -89,11 +89,11 @@ class DownloadManager:
             'bytes_downloaded': 0,
             'total_bytes': None,
             'bytes_per_second': 0.0,
+            'last_progress_timestamp': None,
         }
 
-        pause_event = asyncio.Event()
-        pause_event.set()
-        self._pause_events[task_id] = pause_event
+        pause_control = DownloadStreamControl()
+        self._pause_events[task_id] = pause_control
         
         # Create tracking task
         download_task = asyncio.create_task(
@@ -140,19 +140,23 @@ class DownloadManager:
                     info['bytes_downloaded'] = snapshot.bytes_downloaded
                     info['total_bytes'] = snapshot.total_bytes
                     info['bytes_per_second'] = snapshot.bytes_per_second
+                    pause_control = self._pause_events.get(task_id)
+                    if isinstance(pause_control, DownloadStreamControl):
+                        pause_control.mark_progress(snapshot.timestamp)
+                        info['last_progress_timestamp'] = pause_control.last_progress_timestamp
 
             if original_callback:
                 await self._dispatch_progress(original_callback, snapshot, progress_value)
-        
+
         # Acquire semaphore to limit concurrent downloads
         try:
             async with self._download_semaphore:
-                pause_event = self._pause_events.get(task_id)
-                if pause_event is not None and not pause_event.is_set():
+                pause_control = self._pause_events.get(task_id)
+                if pause_control is not None and pause_control.is_paused():
                     if task_id in self._active_downloads:
                         self._active_downloads[task_id]['status'] = 'paused'
                         self._active_downloads[task_id]['bytes_per_second'] = 0.0
-                    await pause_event.wait()
+                    await pause_control.wait()
 
                 # Update status to downloading
                 if task_id in self._active_downloads:
@@ -478,8 +482,8 @@ class DownloadManager:
             part_path = save_path + '.part'
             metadata_path = os.path.splitext(save_path)[0] + '.metadata.json'
 
-            pause_event = self._pause_events.get(download_id) if download_id else None
-            
+            pause_control = self._pause_events.get(download_id) if download_id else None
+
             # Store file paths in active_downloads for potential cleanup
             if download_id and download_id in self._active_downloads:
                 self._active_downloads[download_id]['file_path'] = save_path
@@ -590,6 +594,8 @@ class DownloadManager:
 
             # Download model file with progress tracking using downloader
             downloader = await get_downloader()
+            if pause_control is not None:
+                pause_control.update_stall_timeout(downloader.stall_timeout)
             last_error = None
             for download_url in download_urls:
                 use_auth = download_url.startswith("https://civitai.com/api/download/")
@@ -602,8 +608,8 @@ class DownloadManager:
                     "use_auth": use_auth,  # Only use authentication for Civitai downloads
                 }
 
-                if pause_event is not None:
-                    download_kwargs["pause_event"] = pause_event
+                if pause_control is not None:
+                    download_kwargs["pause_event"] = pause_control
 
                 success, result = await downloader.download_file(
                     download_url,
@@ -756,9 +762,9 @@ class DownloadManager:
             task = self._download_tasks[download_id]
             task.cancel()
 
-            pause_event = self._pause_events.get(download_id)
-            if pause_event is not None:
-                pause_event.set()
+            pause_control = self._pause_events.get(download_id)
+            if pause_control is not None:
+                pause_control.resume()
 
             # Update status in active downloads
             if download_id in self._active_downloads:
@@ -835,16 +841,14 @@ class DownloadManager:
         if download_id not in self._download_tasks:
             return {'success': False, 'error': 'Download task not found'}
 
-        pause_event = self._pause_events.get(download_id)
-        if pause_event is None:
-            pause_event = asyncio.Event()
-            pause_event.set()
-            self._pause_events[download_id] = pause_event
+        pause_control = self._pause_events.get(download_id)
+        if pause_control is None:
+            return {'success': False, 'error': 'Download task not found'}
 
-        if not pause_event.is_set():
+        if pause_control.is_paused():
             return {'success': False, 'error': 'Download is already paused'}
 
-        pause_event.clear()
+        pause_control.pause()
 
         download_info = self._active_downloads.get(download_id)
         if download_info is not None:
@@ -856,16 +860,28 @@ class DownloadManager:
     async def resume_download(self, download_id: str) -> Dict:
         """Resume a previously paused download."""
 
-        pause_event = self._pause_events.get(download_id)
-        if pause_event is None:
+        pause_control = self._pause_events.get(download_id)
+        if pause_control is None:
             return {'success': False, 'error': 'Download task not found'}
 
-        if pause_event.is_set():
+        if pause_control.is_set():
             return {'success': False, 'error': 'Download is not paused'}
 
-        pause_event.set()
-
         download_info = self._active_downloads.get(download_id)
+        force_reconnect = False
+        if pause_control is not None:
+            elapsed = pause_control.time_since_last_progress()
+            threshold = max(30.0, pause_control.stall_timeout / 2.0)
+            if elapsed is not None and elapsed >= threshold:
+                force_reconnect = True
+                logger.info(
+                    "Forcing reconnect for download %s after %.1f seconds without progress",
+                    download_id,
+                    elapsed,
+                )
+
+        pause_control.resume(force_reconnect=force_reconnect)
+
         if download_info is not None:
             if download_info.get('status') == 'paused':
                 download_info['status'] = 'downloading'

py/services/downloader.py

@@ -36,6 +36,73 @@ class DownloadProgress:
     timestamp: float
 
 
+class DownloadStreamControl:
+    """Synchronize pause/resume requests and reconnect hints for a download."""
+
+    def __init__(self, *, stall_timeout: Optional[float] = None) -> None:
+        self._event = asyncio.Event()
+        self._event.set()
+        self._reconnect_requested = False
+        self.last_progress_timestamp: Optional[float] = None
+        self.stall_timeout: float = float(stall_timeout) if stall_timeout is not None else 120.0
+
+    def is_set(self) -> bool:
+        return self._event.is_set()
+
+    def is_paused(self) -> bool:
+        return not self._event.is_set()
+
+    def set(self) -> None:
+        self._event.set()
+
+    def clear(self) -> None:
+        self._event.clear()
+
+    async def wait(self) -> None:
+        await self._event.wait()
+
+    def pause(self) -> None:
+        self.clear()
+
+    def resume(self, *, force_reconnect: bool = False) -> None:
+        if force_reconnect:
+            self._reconnect_requested = True
+        self.set()
+
+    def request_reconnect(self) -> None:
+        self._reconnect_requested = True
+        self.set()
+
+    def has_reconnect_request(self) -> bool:
+        return self._reconnect_requested
+
+    def consume_reconnect_request(self) -> bool:
+        reconnect = self._reconnect_requested
+        self._reconnect_requested = False
+        return reconnect
+
+    def mark_progress(self, timestamp: Optional[float] = None) -> None:
+        self.last_progress_timestamp = timestamp or datetime.now().timestamp()
+        self._reconnect_requested = False
+
+    def time_since_last_progress(self, *, now: Optional[float] = None) -> Optional[float]:
+        if self.last_progress_timestamp is None:
+            return None
+        reference = now if now is not None else datetime.now().timestamp()
+        return max(0.0, reference - self.last_progress_timestamp)
+
+    def update_stall_timeout(self, stall_timeout: float) -> None:
+        self.stall_timeout = float(stall_timeout)
+
+
+class DownloadRestartRequested(Exception):
+    """Raised when a caller explicitly requests a fresh HTTP stream."""
+
+
+class DownloadStalledError(Exception):
+    """Raised when download progress stalls beyond the configured timeout."""
+
+
 class Downloader:
     """Unified downloader for all HTTP/HTTPS downloads in the application."""
     
@@ -67,6 +134,7 @@ class Downloader:
         self.max_retries = 5
         self.base_delay = 2.0  # Base delay for exponential backoff
         self.session_timeout = 300  # 5 minutes
+        self.stall_timeout = self._resolve_stall_timeout()
         
         # Default headers
         self.default_headers = {
@@ -82,14 +150,38 @@ class Downloader:
         if self._session is None or self._should_refresh_session():
             await self._create_session()
         return self._session
-    
+
     @property
     def proxy_url(self) -> Optional[str]:
         """Get the current proxy URL (initialize if needed)"""
         if not hasattr(self, '_proxy_url'):
             self._proxy_url = None
         return self._proxy_url
-    
+
+    def _resolve_stall_timeout(self) -> float:
+        """Determine the stall timeout from settings or environment."""
+        default_timeout = 120.0
+        settings_timeout = None
+
+        try:
+            settings_manager = get_settings_manager()
+            settings_timeout = settings_manager.get('download_stall_timeout_seconds')
+        except Exception as exc:  # pragma: no cover - defensive guard
+            logger.debug("Failed to read stall timeout from settings: %s", exc)
+
+        raw_value = (
+            settings_timeout
+            if settings_timeout not in (None, "")
+            else os.environ.get('COMFYUI_DOWNLOAD_STALL_TIMEOUT')
+        )
+
+        try:
+            timeout_value = float(raw_value)
+        except (TypeError, ValueError):
+            timeout_value = default_timeout
+
+        return max(30.0, timeout_value)
+
     def _should_refresh_session(self) -> bool:
         """Check if session should be refreshed"""
         if self._session is None:
@@ -181,7 +273,7 @@ class Downloader:
         use_auth: bool = False,
         custom_headers: Optional[Dict[str, str]] = None,
         allow_resume: bool = True,
-        pause_event: Optional[asyncio.Event] = None,
+        pause_event: Optional[DownloadStreamControl] = None,
     ) -> Tuple[bool, str]:
         """
         Download a file with resumable downloads and retry mechanism
@@ -193,7 +285,7 @@ class Downloader:
             use_auth: Whether to include authentication headers (e.g., CivitAI API key)
             custom_headers: Additional headers to include in request
             allow_resume: Whether to support resumable downloads
-            pause_event: Optional event that, when cleared, will pause streaming until set again
+            pause_event: Optional stream control used to pause/resume and request reconnects
             
         Returns:
             Tuple[bool, str]: (success, save_path or error message)
@@ -307,51 +399,88 @@ class Downloader:
                     last_progress_report_time = datetime.now()
                     progress_samples: deque[tuple[datetime, int]] = deque()
                     progress_samples.append((last_progress_report_time, current_size))
-                    
+
                     # Ensure directory exists
                     os.makedirs(os.path.dirname(save_path), exist_ok=True)
-                    
+
                     # Stream download to file with progress updates
                     loop = asyncio.get_running_loop()
                     mode = 'ab' if (allow_resume and resume_offset > 0) else 'wb'
+                    control = pause_event
+
+                    if control is not None:
+                        control.update_stall_timeout(self.stall_timeout)
+
                     with open(part_path, mode) as f:
-                        async for chunk in response.content.iter_chunked(self.chunk_size):
-                            if pause_event is not None and not pause_event.is_set():
-                                await pause_event.wait()
-                            if chunk:
-                                # Run blocking file write in executor
-                                await loop.run_in_executor(None, f.write, chunk)
-                                current_size += len(chunk)
+                        while True:
+                            active_stall_timeout = control.stall_timeout if control else self.stall_timeout
 
-                                # Limit progress update frequency to reduce overhead
-                                now = datetime.now()
-                                time_diff = (now - last_progress_report_time).total_seconds()
+                            if control is not None:
+                                if control.is_paused():
+                                    await control.wait()
+                                    resume_time = datetime.now()
+                                    last_progress_report_time = resume_time
+                                    if control.consume_reconnect_request():
+                                        raise DownloadRestartRequested(
+                                            "Reconnect requested after resume"
+                                        )
+                                elif control.consume_reconnect_request():
+                                    raise DownloadRestartRequested("Reconnect requested")
 
-                                if progress_callback and time_diff >= 1.0:
-                                    progress_samples.append((now, current_size))
-                                    cutoff = now - timedelta(seconds=5)
-                                    while progress_samples and progress_samples[0][0] < cutoff:
-                                        progress_samples.popleft()
+                            try:
+                                chunk = await asyncio.wait_for(
+                                    response.content.read(self.chunk_size),
+                                    timeout=active_stall_timeout,
+                                )
+                            except asyncio.TimeoutError as exc:
+                                logger.warning(
+                                    "Download stalled for %.1f seconds without progress from %s",
+                                    active_stall_timeout,
+                                    url,
+                                )
+                                raise DownloadStalledError(
+                                    f"No data received for {active_stall_timeout:.1f} seconds"
+                                ) from exc
 
-                                    percent = (current_size / total_size) * 100 if total_size else 0.0
-                                    bytes_per_second = 0.0
-                                    if len(progress_samples) >= 2:
-                                        first_time, first_bytes = progress_samples[0]
-                                        last_time, last_bytes = progress_samples[-1]
-                                        elapsed = (last_time - first_time).total_seconds()
-                                        if elapsed > 0:
-                                            bytes_per_second = (last_bytes - first_bytes) / elapsed
+                            if not chunk:
+                                break
 
-                                    progress_snapshot = DownloadProgress(
-                                        percent_complete=percent,
-                                        bytes_downloaded=current_size,
-                                        total_bytes=total_size or None,
-                                        bytes_per_second=bytes_per_second,
-                                        timestamp=now.timestamp(),
-                                    )
+                            # Run blocking file write in executor
+                            await loop.run_in_executor(None, f.write, chunk)
+                            current_size += len(chunk)
 
-                                    await self._dispatch_progress_callback(progress_callback, progress_snapshot)
-                                    last_progress_report_time = now
+                            now = datetime.now()
+                            if control is not None:
+                                control.mark_progress(timestamp=now.timestamp())
+
+                            # Limit progress update frequency to reduce overhead
+                            time_diff = (now - last_progress_report_time).total_seconds()
+
+                            if progress_callback and time_diff >= 1.0:
+                                progress_samples.append((now, current_size))
+                                cutoff = now - timedelta(seconds=5)
+                                while progress_samples and progress_samples[0][0] < cutoff:
+                                    progress_samples.popleft()
+
+                                percent = (current_size / total_size) * 100 if total_size else 0.0
+                                bytes_per_second = 0.0
+                                if len(progress_samples) >= 2:
+                                    first_time, first_bytes = progress_samples[0]
+                                    last_time, last_bytes = progress_samples[-1]
+                                    elapsed = (last_time - first_time).total_seconds()
+                                    if elapsed > 0:
+                                        bytes_per_second = (last_bytes - first_bytes) / elapsed
+
+                                progress_snapshot = DownloadProgress(
+                                    percent_complete=percent,
+                                    bytes_downloaded=current_size,
+                                    total_bytes=total_size or None,
+                                    bytes_per_second=bytes_per_second,
+                                    timestamp=now.timestamp(),
+                                )
+
+                                await self._dispatch_progress_callback(progress_callback, progress_snapshot)
+                                last_progress_report_time = now
                     
                     # Download completed successfully
                     # Verify file size integrity before finalizing
@@ -447,11 +576,17 @@ class Downloader:
                     
                     return True, save_path
                     
-            except (aiohttp.ClientError, aiohttp.ClientPayloadError,
-                    aiohttp.ServerDisconnectedError, asyncio.TimeoutError) as e:
+            except (
+                aiohttp.ClientError,
+                aiohttp.ClientPayloadError,
+                aiohttp.ServerDisconnectedError,
+                asyncio.TimeoutError,
+                DownloadStalledError,
+                DownloadRestartRequested,
+            ) as e:
                 retry_count += 1
                 logger.warning(f"Network error during download (attempt {retry_count}/{self.max_retries + 1}): {e}")
-                
+
                 if retry_count <= self.max_retries:
                     # Calculate delay with exponential backoff
                     delay = self.base_delay * (2 ** (retry_count - 1))

tests/services/test_download_manager.py

@@ -1,5 +1,6 @@
 import asyncio
 import os
+from datetime import datetime
 from pathlib import Path
 from typing import Optional
 from types import SimpleNamespace
@@ -8,6 +9,7 @@ from unittest.mock import AsyncMock
 import pytest
 
 from py.services.download_manager import DownloadManager
+from py.services.downloader import DownloadStreamControl
 from py.services import download_manager
 from py.services.service_registry import ServiceRegistry
 from py.services.settings_manager import SettingsManager, get_settings_manager
@@ -528,9 +530,8 @@ async def test_pause_download_updates_state():
 
     download_id = "dl"
     manager._download_tasks[download_id] = object()
-    pause_event = asyncio.Event()
-    pause_event.set()
-    manager._pause_events[download_id] = pause_event
+    pause_control = DownloadStreamControl()
+    manager._pause_events[download_id] = pause_control
     manager._active_downloads[download_id] = {
         "status": "downloading",
         "bytes_per_second": 42.0,
@@ -557,8 +558,10 @@ async def test_resume_download_sets_event_and_status():
     manager = DownloadManager()
 
     download_id = "dl"
-    pause_event = asyncio.Event()
-    manager._pause_events[download_id] = pause_event
+    pause_control = DownloadStreamControl()
+    pause_control.pause()
+    pause_control.mark_progress()
+    manager._pause_events[download_id] = pause_control
     manager._active_downloads[download_id] = {
         "status": "paused",
         "bytes_per_second": 0.0,
@@ -571,13 +574,32 @@ async def test_resume_download_sets_event_and_status():
     assert manager._active_downloads[download_id]["status"] == "downloading"
 
 
+async def test_resume_download_requests_reconnect_for_stalled_stream():
+    manager = DownloadManager()
+
+    download_id = "dl"
+    pause_control = DownloadStreamControl(stall_timeout=40)
+    pause_control.pause()
+    pause_control.last_progress_timestamp = (datetime.now().timestamp() - 120)
+    manager._pause_events[download_id] = pause_control
+    manager._active_downloads[download_id] = {
+        "status": "paused",
+        "bytes_per_second": 0.0,
+    }
+
+    result = await manager.resume_download(download_id)
+
+    assert result == {"success": True, "message": "Download resumed successfully"}
+    assert pause_control.is_set() is True
+    assert pause_control.has_reconnect_request() is True
+
+
 async def test_resume_download_rejects_when_not_paused():
     manager = DownloadManager()
 
     download_id = "dl"
-    pause_event = asyncio.Event()
-    pause_event.set()
-    manager._pause_events[download_id] = pause_event
+    pause_control = DownloadStreamControl()
+    manager._pause_events[download_id] = pause_control
 
     result = await manager.resume_download(download_id)
 

tests/services/test_downloader.py

@@ -1,6 +1,7 @@
 import asyncio
 from datetime import datetime
 from pathlib import Path
+from typing import Sequence
 
 import pytest
 
@@ -8,13 +9,24 @@ from py.services.downloader import Downloader
 
 
 class FakeStream:
-    def __init__(self, chunks):
+    def __init__(self, chunks: Sequence[Sequence] | Sequence[bytes]):
         self._chunks = list(chunks)
 
-    async def iter_chunked(self, _chunk_size):
-        for chunk in self._chunks:
+    async def read(self, _chunk_size: int) -> bytes:
+        if not self._chunks:
             await asyncio.sleep(0)
-            yield chunk
+            return b""
+
+        item = self._chunks.pop(0)
+        delay = 0.0
+        payload = item
+
+        if isinstance(item, tuple):
+            payload = item[0]
+            delay = item[1]
+
+        await asyncio.sleep(delay)
+        return payload
 
 
 class FakeResponse:
@@ -53,6 +65,12 @@ def _build_downloader(responses, *, max_retries=0):
     downloader._session = fake_session
     downloader._session_created_at = datetime.now()
     downloader._proxy_url = None
+    async def _noop_create_session():
+        downloader._session = fake_session
+        downloader._session_created_at = datetime.now()
+        downloader._proxy_url = None
+
+    downloader._create_session = _noop_create_session  # type: ignore[assignment]
     return downloader
 
 
@@ -123,3 +141,34 @@ async def test_download_file_succeeds_when_sizes_match(tmp_path):
     assert success is True
     assert Path(result_path).read_bytes() == payload
     assert not Path(str(target_path) + ".part").exists()
+
+
+@pytest.mark.asyncio
+async def test_download_file_recovers_from_stall(tmp_path):
+    target_path = tmp_path / "model" / "file.bin"
+    target_path.parent.mkdir()
+
+    payload = b"abcdef"
+
+    responses = [
+        lambda: FakeResponse(
+            status=200,
+            headers={"content-length": str(len(payload))},
+            chunks=[(b"abc", 0.0), (b"def", 0.1)],
+        ),
+        lambda: FakeResponse(
+            status=206,
+            headers={"content-length": "3", "Content-Range": "bytes 3-5/6"},
+            chunks=[(b"def", 0.0)],
+        ),
+    ]
+
+    downloader = _build_downloader(responses, max_retries=1)
+    downloader.stall_timeout = 0.05
+
+    success, result_path = await downloader.download_file("https://example.com/file", str(target_path))
+
+    assert success is True
+    assert Path(result_path).read_bytes() == payload
+    assert downloader._session._get_calls == 2
+    assert not Path(str(target_path) + ".part").exists()