Files
mule-image/backend/app/tasks/thumbs.py
root f090a809a9 fix: harden pipeline — retries, acks_late, time limits, session safety
Addresses 16 robustness, transparency, and performance issues across
the Celery media processing pipeline:

Critical:
- Singleton DB engine in vision tasks (was leaking one per task call)
- acks_late + task_reject_on_worker_lost so crashed workers don't lose tasks
- Global soft/hard time limits (5/10 min) to prevent hung worker slots
- Thumbnail copy-before-resize (in-place mutation degraded larger sizes)
- backfill_vision now checks each task type independently (OCR, faces, etc.)
- Parameterized LIMIT in backfill_vision (was f-string SQL injection)

High:
- try/except + retry(max=3) on all vision inference tasks
- extract_metadata writes processing_error on exiftool failure
- PIL Image handles closed in _load_thumb/_load_original
- Scan progress Redis keys auto-expire after 1 hour
- Watcher lock renewal is wall-clock based (30s) not event-count based
- worker_process_init signal warms up vision models on startup

Medium:
- Explicit task_routes for every task name (wildcards never matched)
- app.services.metadata added to Celery include list
- POST /maintenance/recover-stuck endpoint for photos stuck in processing
- Docker healthchecks for worker-light, worker-vision, and Redis
- Task ID in vision log lines for distributed tracing
- Bare except:pass narrowed to specific exceptions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-04-13 08:57:10 +02:00

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"""
Celery tasks for thumbnail generation
"""
import os
import asyncio
from pathlib import Path
import logging
from typing import Tuple, Optional
import json
from celery import shared_task
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from PIL import Image
import imageio
from pillow_heif import register_heif_opener
import ffmpeg
# Try to import optional libraries
try:
import pyvips
PYVIPS_AVAILABLE = True
except ImportError:
PYVIPS_AVAILABLE = False
print("pyvips not available, using Pillow for image processing")
try:
import rawpy
RAWPY_AVAILABLE = True
except ImportError:
RAWPY_AVAILABLE = False
print("rawpy not available, using exiftool for RAW preview extraction")
from app.database import AsyncSessionLocal
from app.models import Photo
from app.config import settings
# Register HEIF opener with Pillow
register_heif_opener()
logger = logging.getLogger(__name__)
# Thumbnail sizes configuration
THUMB_SIZES = {
'small': settings.thumbnails.small,
'medium': settings.thumbnails.medium,
'large': settings.thumbnails.large
}
def get_thumb_path(photo_id: str, size: str, user_id: str = None) -> str:
"""Get the path for a thumbnail file.
When user_id is provided, thumbnails are stored under a user-specific
subdirectory to enforce isolation between users.
"""
if user_id:
thumb_dir = f"/data/thumbs/{user_id}/{photo_id}"
else:
thumb_dir = f"/data/thumbs/{photo_id}"
os.makedirs(thumb_dir, exist_ok=True)
return f"{thumb_dir}/{size}.{settings.thumbnails.format}"
def process_standard_image(filepath: str) -> Image.Image:
"""Process standard image formats (JPEG, PNG, etc.)"""
return Image.open(filepath)
def process_raw_image(filepath: str) -> Image.Image:
"""Process RAW image formats"""
if RAWPY_AVAILABLE:
try:
with rawpy.imread(filepath) as raw:
# Use half_size for faster processing
rgb = raw.postprocess(use_camera_wb=True, half_size=True)
# Convert numpy array to PIL Image
return Image.fromarray(rgb, 'RGB')
except Exception as e:
logger.error(f"Error processing RAW file {filepath}: {e}")
# Try to extract embedded JPEG preview
return extract_raw_preview(filepath)
else:
# Use exiftool to extract embedded preview
return extract_raw_preview(filepath)
def extract_raw_preview(filepath: str) -> Optional[Image.Image]:
"""Extract embedded JPEG preview from RAW file"""
try:
# Use exiftool to extract preview
import subprocess
import tempfile
with tempfile.NamedTemporaryFile(suffix='.jpg', delete=False) as tmp:
cmd = ['exiftool', '-b', '-PreviewImage', filepath]
result = subprocess.run(cmd, capture_output=True)
if result.returncode == 0 and result.stdout:
tmp.write(result.stdout)
tmp.flush()
return Image.open(tmp.name)
except Exception as e:
logger.error(f"Error extracting RAW preview from {filepath}: {e}")
return None
def process_heic_image(filepath: str) -> Image.Image:
"""Process HEIC/HEIF image formats"""
try:
# Use pillow-heif to open the image
img = Image.open(filepath)
# Convert to RGB if needed
if img.mode != 'RGB':
img = img.convert('RGB')
return img
except Exception as e:
logger.error(f"Error processing HEIC file {filepath}: {e}")
raise
def process_video_thumbnail(filepath: str) -> Image.Image:
"""Extract a still frame from a video file as a PIL Image."""
import tempfile
from io import BytesIO
tmp_path: Optional[str] = None
try:
# Find a usable seek timestamp. Some camera MOVs only expose
# duration at the format level, and stream 0 isn't always the
# video stream — search explicitly and fall back to the format
# duration, then to t=0 if neither is available.
probe = ffmpeg.probe(filepath)
duration: Optional[float] = None
for stream_info in probe.get('streams', []):
if stream_info.get('codec_type') != 'video':
continue
raw_duration = stream_info.get('duration')
if raw_duration is not None:
try:
duration = float(raw_duration)
break
except (TypeError, ValueError):
pass
if duration is None:
raw_duration = probe.get('format', {}).get('duration')
if raw_duration is not None:
try:
duration = float(raw_duration)
except (TypeError, ValueError):
duration = None
# Seek to 10% in for a representative frame; clamp very short
# clips to t=0 so we don't seek past the end.
timestamp = max(0.0, (duration or 0.0) * 0.1)
# NamedTemporaryFile creates the file on disk, so we MUST tell
# ffmpeg to overwrite it (otherwise it prompts on stdin and the
# call hangs/fails — which is why videos were getting the gray
# placeholder). We close the handle immediately and clean up
# in `finally` ourselves.
with tempfile.NamedTemporaryFile(suffix='.jpg', delete=False) as tmp:
tmp_path = tmp.name
stream = ffmpeg.input(filepath, ss=timestamp)
stream = ffmpeg.output(
stream,
tmp_path,
vframes=1,
format='image2',
vcodec='mjpeg',
)
ffmpeg.run(
stream,
capture_stdout=True,
capture_stderr=True,
overwrite_output=True,
)
# Load the frame fully into memory so we can delete the temp
# file immediately. Pillow's `Image.open` is lazy, which would
# otherwise leave the file dangling.
with open(tmp_path, 'rb') as fh:
data = fh.read()
if not data:
raise RuntimeError("ffmpeg produced an empty frame")
return Image.open(BytesIO(data)).copy()
except ffmpeg.Error as e:
stderr = (e.stderr or b'').decode('utf-8', errors='replace')
logger.error(
f"ffmpeg failed extracting video thumbnail from {filepath}: {stderr}"
)
return create_placeholder_thumbnail('video')
except Exception as e:
logger.error(f"Error extracting video thumbnail from {filepath}: {e}")
return create_placeholder_thumbnail('video')
finally:
if tmp_path and os.path.exists(tmp_path):
try:
os.unlink(tmp_path)
except OSError:
pass
def create_placeholder_thumbnail(media_type: str) -> Image.Image:
"""Create a placeholder thumbnail for failed processing"""
# Create a simple gray placeholder
img = Image.new('RGB', (640, 480), color=(128, 128, 128))
return img
def auto_rotate_image(image: Image.Image) -> Image.Image:
"""Auto-rotate image based on EXIF orientation"""
try:
# Get EXIF data
exif = image._getexif()
if exif:
orientation = exif.get(274) # Orientation tag
rotation_map = {
3: 180,
6: 270, # Note: PIL uses different rotation values than vips
8: 90
}
if orientation in rotation_map:
image = image.rotate(rotation_map[orientation], expand=True)
except (AttributeError, KeyError, TypeError):
pass # No orientation data available
return image
def generate_thumbnail(image: Image.Image, size: int, output_path: str):
"""Generate a thumbnail of the specified size.
Works on a copy so the caller's image is never mutated — this is
critical because the thumbnail loop iterates multiple sizes and
in-place shrinking would degrade later (larger) sizes.
"""
img = image.copy()
img.thumbnail((size, size), Image.Resampling.LANCZOS)
img.save(
output_path,
'WEBP',
quality=settings.thumbnails.quality,
method=4 # Balance between speed and compression
)
img.close()
@shared_task(bind=True, name='generate_thumbnails')
def generate_thumbnails(self, photo_id: str):
"""Generate thumbnails for a photo"""
return asyncio.run(_generate_thumbnails_async(photo_id, self))
async def _generate_thumbnails_async(photo_id: str, task):
"""Async implementation of thumbnail generation"""
async with AsyncSessionLocal() as session:
# Declared up front so the except block below can safely check it
# even if the initial SELECT raises (e.g. asyncpg transport error).
photo: Optional[Photo] = None
try:
# Get photo from database
result = await session.execute(
select(Photo).where(Photo.id == photo_id)
)
photo = result.scalar_one_or_none()
if not photo:
logger.error(f"Photo not found: {photo_id}")
return {'status': 'error', 'message': 'Photo not found'}
# Check if file exists
if not os.path.exists(photo.filepath):
logger.error(f"File not found: {photo.filepath}")
photo.processing_status = 'failed'
photo.processing_error = 'File not found'
await session.commit()
return {'status': 'error', 'message': 'File not found'}
# Update processing status
photo.processing_status = 'processing'
await session.commit()
# Load and process the image based on type
image = None
if photo.media_type == 'photo':
image = process_standard_image(photo.filepath)
elif photo.media_type == 'raw':
image = process_raw_image(photo.filepath)
elif photo.media_type == 'heic':
image = process_heic_image(photo.filepath)
elif photo.media_type == 'video':
image = process_video_thumbnail(photo.filepath)
else:
logger.error(f"Unsupported media type: {photo.media_type}")
image = create_placeholder_thumbnail(photo.media_type)
if not image:
raise Exception("Failed to process image")
# Auto-rotate based on EXIF
image = auto_rotate_image(image)
# Store original dimensions
photo.width = image.width
photo.height = image.height
# Perceptual hash from the original-resolution decoded frame.
# pHash is robust to resize/recompression but the thumbnail
# loop below mutates `image` in place, so this MUST run before
# the loop sees it. Failures are non-fatal — phash is a
# nice-to-have, not a blocker for thumbnail generation.
try:
import imagehash
photo.phash = str(imagehash.phash(image)) # 16-char hex
except Exception as e:
logger.warning(f"phash failed for {photo_id}: {e}")
photo.phash = None
# Generate thumbnails for each size
for size_name, size_value in THUMB_SIZES.items():
thumb_path = get_thumb_path(photo_id, size_name, photo.user_id)
generate_thumbnail(image, size_value, thumb_path)
# Update database with thumbnail path
setattr(photo, f'thumb_{size_name}', thumb_path)
# Update progress
task.update_state(
state='PROGRESS',
meta={'current_size': size_name, 'photo_id': photo_id}
)
# Update processing status
photo.processing_status = 'completed'
photo.processing_error = None
await session.commit()
logger.info(f"Thumbnails generated for photo {photo_id}")
# Dispatch vision pipeline only after thumbnails succeeded —
# vision tasks need the generated thumbnails to run inference.
try:
from app.tasks.vision import vision_fanout
vision_fanout.delay(photo_id)
except Exception as e:
logger.warning(f"Could not dispatch vision_fanout for {photo_id}: {e}")
return {'status': 'success', 'photo_id': photo_id}
except Exception as e:
logger.error(f"Error generating thumbnails for {photo_id}: {e}")
# Update error status. If the session is in a bad state (e.g.
# the original failure was a transport error) rollback first so
# the status write has a clean transaction to commit into.
try:
await session.rollback()
except Exception:
pass
if photo is not None:
try:
photo.processing_status = 'failed'
photo.processing_error = str(e)
await session.commit()
except Exception:
logger.exception(
f"Could not mark photo {photo_id} as failed"
)
return {'status': 'error', 'message': str(e)}
@shared_task(name='regenerate_all_thumbnails')
def regenerate_all_thumbnails():
"""Regenerate thumbnails for all photos"""
return asyncio.run(_regenerate_all_thumbnails_async())
async def _regenerate_all_thumbnails_async():
"""Async implementation of regenerating all thumbnails.
Queue order matters on first-boot and recovery runs: we dispatch
newest-first (by EXIF taken_at, fallback added_at) so the user's
most recent photos become fully-indexed before the 2012 archive even
starts. Picking up the library in pipeline order means the grid,
timeline and All Photos view populate top-down instead of the worker
chewing through random insertion-order rows while the UI still
shows grey placeholders.
"""
async with AsyncSessionLocal() as session:
# Get all photos that need thumbnails, newest first.
result = await session.execute(
select(Photo)
.where(Photo.processing_status.in_(['pending', 'failed']))
.order_by(
Photo.taken_at.desc().nullslast(),
Photo.added_at.desc().nullslast(),
)
)
photos = result.scalars().all()
logger.info(f"Regenerating thumbnails for {len(photos)} photos")
for photo in photos:
generate_thumbnails.delay(photo.id)
return {'status': 'queued', 'count': len(photos)}
# ── Perceptual hash backfill ────────────────────────────────────────────
#
# When phash was added post-launch, every existing photo has phash=NULL.
# This task fills them in by reading the existing thumb_large (the cheap
# option — pHash is robust to scale, and the thumb is already on local
# disk so we avoid re-decoding the original RAW/HEIC). Falls back to the
# original filepath if the thumb isn't available for some reason. Runs
# in batches to keep memory bounded and to give the user incremental
# progress visible in the worker logs.
@shared_task(name='backfill_phashes')
def backfill_phashes():
"""Compute and persist phash for every photo currently missing one."""
return asyncio.run(_backfill_phashes_async())
async def _backfill_phashes_async():
import imagehash
from PIL import Image as _PILImage
BATCH = 100
total_done = 0
total_failed = 0
async with AsyncSessionLocal() as session:
while True:
# Newest-first so the recent end of the library gets phashes
# (and therefore duplicate detection) ahead of the archive.
result = await session.execute(
select(Photo)
.where(Photo.phash.is_(None))
.where(Photo.processing_status == 'completed')
.order_by(
Photo.taken_at.desc().nullslast(),
Photo.added_at.desc().nullslast(),
)
.limit(BATCH)
)
batch = result.scalars().all()
if not batch:
break
for photo in batch:
source = photo.thumb_large or photo.filepath
try:
if not source or not os.path.exists(source):
photo.phash = None
total_failed += 1
continue
with _PILImage.open(source) as im:
photo.phash = str(imagehash.phash(im))
total_done += 1
except Exception as e:
logger.warning(f"phash backfill failed for {photo.id}: {e}")
total_failed += 1
await session.commit()
logger.info(
f"Backfilled phashes: {total_done} done, {total_failed} failed"
)
return {
'status': 'success',
'computed': total_done,
'failed': total_failed,
}
@shared_task(name='regroup_duplicates')
def regroup_duplicates_task():
"""Full recompute of duplicate groups (pHash + CLIP similarity).
Used by the Settings → Re-detect duplicates button."""
from app.services.duplicates import regroup_duplicates
return asyncio.run(regroup_duplicates())
@shared_task(name='incremental_regroup_duplicates')
def incremental_regroup_duplicates_task(since_iso: str | None = None):
"""Incremental duplicate detection for newly added photos.
Compares only photos added after `since_iso` against the full library
using CLIP vector similarity (O(new × log N) via HNSW) plus pHash.
Default post-scan path — much faster than a full regroup."""
from app.services.duplicates import incremental_regroup
from datetime import datetime, timezone
since = None
if since_iso:
since = datetime.fromisoformat(since_iso)
return asyncio.run(incremental_regroup(since=since))