Run OCR on image after saving (synchronously!) (#20)

docker-compose.yml

@@ -33,5 +33,11 @@ services:
     depends_on:
       db:
         condition: service_healthy
-    restart: unless-stopped
+      celery_redis:
+        condition: service_healthy
+    restart: unless-stopped      
+  celery_redis:
+    image: redis
+    healthcheck:
+      test: ["CMD", "redis-cli","ping"]
 

imzam/__init__.py

@@ -0,0 +1,5 @@
+# This will make sure the app is always imported when
+# Django starts so that shared_task will use this app.
+from .celery import app as celery_app
+
+__all__ = ('celery_app',)

imzam/celery.py

@@ -0,0 +1,22 @@
+import os
+
+from celery import Celery
+
+# Set the default Django settings module for the 'celery' program.
+os.environ.setdefault('DJANGO_SETTINGS_MODULE', 'imzam.settings')
+
+app = Celery('imzam')
+
+# Using a string here means the worker doesn't have to serialize
+# the configuration object to child processes.
+# - namespace='CELERY' means all celery-related configuration keys
+#   should have a `CELERY_` prefix.
+app.config_from_object('django.conf:settings', namespace='CELERY')
+
+# Load task modules from all registered Django apps.
+app.autodiscover_tasks()
+
+
+@app.task(bind=True, ignore_result=True)
+def debug_task(self):
+    print(f'Request: {self.request!r}')

imzam/local_settings.example_dev.py

@@ -24,3 +24,10 @@
 
 OIDC_RP_CLIENT_ID = ''
 OIDC_RP_CLIENT_SECRET = ''
+
+# ================================================================
+# Celery config
+# ================================================================
+# Setting CELERY_TASK_ALWAYS_EAGER executes all celery tasks locally by blocking until the task returns. Set this to False
+# if you have a local running instance of redis and use the command 'python manage.py celery_worker run' to start the celery worker
+CELERY_TASK_ALWAYS_EAGER = True

imzam/settings.py

@@ -234,6 +234,18 @@
     username=os.getenv("MQTT_ZAMIP_USERNAME", "inv.zam.haus-django"),
     password=os.getenv("MQTT_ZAMIP_PASSWORD", ""))
 
+# ================================================================
+# Celery config
+# ================================================================
+CELERY_BROKER_CONNECTION_RETRY_ON_STARTUP = True
+CELERY_BROKER_CONNECTION_MAX_RETRIES = 5
+
+# Setting CELERY_TASK_ALWAYS_EAGER executes all celery tasks locally by blocking until the task returns. Set this to False
+# if you have a local running instance of redis and use the command 'python manage.py celery_worker run' to start the celery worker
+CELERY_TASK_ALWAYS_EAGER = False
+
+CELERY_BROKER_URL = "redis://celery_redis"
+
 
 # Overwrite default settings with local_settings.py configuration
 if not os.getenv("IGNORE_LOCAL_SETTINGS", False):

inventory/management/commands/celery_worker.py

@@ -0,0 +1,49 @@
+"""
+Utility script for starting Celery worker
+"""
+import shlex
+import subprocess
+import imzam.celery
+from django.core.management.base import BaseCommand, CommandError
+
+CELERY_APP_NAME = "imzam"
+
+
+def start_celery(background=False):
+    cmd = shlex.split(f'celery -A {CELERY_APP_NAME} worker -l INFO')
+    if background:
+        subprocess.Popen(cmd, stdout=subprocess.DEVNULL,
+                         stderr=subprocess.DEVNULL)
+    else:
+        subprocess.call(cmd)
+
+
+def shutdown_celery():
+    cmd = shlex.split(f'celery -A {CELERY_APP_NAME} control shutdown')
+    subprocess.call(cmd)
+
+
+class Command(BaseCommand):
+
+    def add_arguments(self, parser):
+        parser.add_argument(
+            'command', help="Command for celery worker (either 'run' or 'stop')", type=str)
+        parser.add_argument('--background', action='store_true',
+                            default=False, help="Run worker in background")
+
+    def handle(self, *args, **kwargs):
+        command = kwargs['command']
+        background = kwargs['background']
+        if command == 'run':
+            print(
+                f'Starting celery worker{" in background" if background else ""}')
+            start_celery(background)
+        elif command == 'stop':
+            print('Stopping celery worker')
+            if background:
+                raise CommandError(
+                    f"Invalid option '--background' for 'stop' command")
+            shutdown_celery()
+        else:
+            raise CommandError(
+                f"Unknown command: must be either 'run' or 'stop'.")

inventory/models.py

@@ -1,26 +1,27 @@
-from datetime import datetime
-from string import Template
 import urllib.parse
-
-from inventory.ocr_util import ocr_on_image_path
-from paho.mqtt import client as mqttc
+from datetime import datetime
 from pydoc import describe
-from typing_extensions import Required
+from string import Template
 from xml.etree.ElementTree import Comment
-from django.db import models
-from django.core import validators
+
 from computedfields.models import ComputedFieldsModel, computed
+from django.conf import settings
+from django.core import validators
+from django.db import models
+from django.db.models.signals import pre_delete
+from django.dispatch.dispatcher import receiver
 from django.forms import ValidationError
 from django.urls import reverse
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
-from django.conf import settings
-from django.utils.translation import gettext_lazy as _
 from django.utils.timezone import make_aware
-from django.db.models.signals import pre_delete
-from django.dispatch.dispatcher import receiver
+from django.utils.translation import gettext_lazy as _
+from paho.mqtt import client as mqttc
 from sorl.thumbnail import delete
+from typing_extensions import Required
 
+from inventory.ocr_util import ocr_on_image_path
+from inventory.tasks import run_ocr_on_item_image
 
 # Create your models here.
 
@@ -32,7 +33,8 @@ class Meta:
 
     # TODO use UUID as id?
     # id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
-    name = models.CharField(_("item name"), max_length=512, blank=True, null=True)
+    name = models.CharField(
+        _("item name"), max_length=512, blank=True, null=True)
     description = models.TextField(_("description"), blank=True)
     # TODO implement signal for automatic adoption by parent_location
     # https://stackoverflow.com/questions/43857902/django-set-foreign-key-to-parent_location-value-on-delete
@@ -111,9 +113,12 @@ def get_item_upload_path(instance, filename):
 
 class ItemImage(models.Model):
     image = models.ImageField(_("image"), upload_to=get_item_upload_path)
-    description = models.CharField(_("description"), max_length=512, blank=True)
-    item = models.ForeignKey("Item", on_delete=models.CASCADE, verbose_name=_("item"))
-    ocr_text = models.TextField(_("ocr text"), blank=True, null=True, editable=False)
+    description = models.CharField(
+        _("description"), max_length=512, blank=True)
+    item = models.ForeignKey(
+        "Item", on_delete=models.CASCADE, verbose_name=_("item"))
+    ocr_text = models.TextField(
+        _("ocr text"), blank=True, null=True, editable=False)
     ocr_timestamp = models.DateTimeField(blank=True, null=True)
 
     def image_tag(self, location=None):
@@ -126,12 +131,29 @@ def image_tag(self, location=None):
     def update_ocr_text(self, ocr_text):
         self.ocr_text = ocr_text
         self.ocr_timestamp = make_aware(datetime.utcnow())
-        self.save()
+        self.save(update_fields=['ocr_text', 'ocr_timestamp'])
 
     def run_ocr(self):
-        ocr_text = ocr_on_image_path(self.image.path)
-        self.update_ocr_text(ocr_text)
-        return ocr_text
+        self.ocr_text = ocr_on_image_path(self.image.path)
+        self.ocr_timestamp = make_aware(datetime.utcnow())
+
+    def save_ocr_text(self):
+        super().save(update_fields=['ocr_text', 'ocr_timestamp'])
+
+    def save(
+        self, force_insert=False, force_update=False, using=None, update_fields=None
+    ):
+        if update_fields is not None and 'image' not in update_fields:
+            return super().save(force_insert, force_update, using, update_fields)
+        try:
+            original_instance = ItemImage.objects.get(pk=self.pk)
+        except ItemImage.DoesNotExist:
+            original_instance = None
+        super().save(force_insert, force_update, using, update_fields)
+        # Retrieve new instance with updated file path
+        new_instance = ItemImage.objects.get(pk=self.pk)
+        if original_instance is None or (original_instance.ocr_text == new_instance.ocr_text and original_instance.image.path != new_instance.image.path):
+            run_ocr_on_item_image.delay(self.pk)
 
 
 @receiver(pre_delete, sender=ItemImage)
@@ -144,8 +166,10 @@ def delete_image(sender, instance, **kwargs):
 
 class ItemFile(models.Model):
     file = models.FileField(_("file"), upload_to=get_item_upload_path)
-    description = models.CharField(_("description"), max_length=512, blank=True)
-    item = models.ForeignKey("Item", on_delete=models.CASCADE, verbose_name=_("file"))
+    description = models.CharField(
+        _("description"), max_length=512, blank=True)
+    item = models.ForeignKey(
+        "Item", on_delete=models.CASCADE, verbose_name=_("file"))
 
 
 @receiver(pre_delete, sender=ItemImage)
@@ -168,7 +192,8 @@ class ItemBarcode(models.Model):
         blank=True,
         verbose_name=_("type"),
     )
-    item = models.ForeignKey("Item", on_delete=models.CASCADE, verbose_name=_("Item"))
+    item = models.ForeignKey(
+        "Item", on_delete=models.CASCADE, verbose_name=_("Item"))
 
     def __str__(self):
         return f"{repr(self.data)} ({self.type})"
@@ -334,12 +359,12 @@ def get_lablary_url(self, location=None):
 
     def image_tag(self, location=None):
         return mark_safe(
-            '<img width="100%%" src="%s" />' % escape(self.get_lablary_url(location))
+            '<img width="100%%" src="%s" />' % escape(
+                self.get_lablary_url(location))
         )
     image_tag.short_description = "Rendered label"
     image_tag.allow_tags = True
 
-
     def send_to_printer(self, location=None):
         c = mqttc.Client(**settings.MQTT_CLIENT_KWARGS)
         if settings.MQTT_SERVER_SSL:
@@ -348,7 +373,8 @@ def send_to_printer(self, location=None):
             c.username_pw_set(**settings.MQTT_PASSWORD_AUTH)
         c.connect(**settings.MQTT_SERVER_KWARGS)
         msg = c.publish(
-            settings.MQTT_PRINTER_TOPIC, payload=self.generate_label_zpl(location)
+            settings.MQTT_PRINTER_TOPIC, payload=self.generate_label_zpl(
+                location)
         )
         # Messages to forbidden topics wil be silently ignored! Nothing we can do about it.
         msg.wait_for_publish()
@@ -420,7 +446,8 @@ def clean(self):
         # ensure uniqueness on short_name and name per type, if type demands it
         if self.type.unique:
             # get all locations with a LocType defined as unique
-            unique_locs = Location.objects.exclude(pk=self.pk).filter(type__unique=True)
+            unique_locs = Location.objects.exclude(
+                pk=self.pk).filter(type__unique=True)
             if self.short_name in unique_locs.values_list("short_name", flat=True):
                 raise ValidationError(
                     {"short_name": "Short name must be unique, as defined by type."}
@@ -458,15 +485,17 @@ def __str__(self):
 
     @computed(
         models.CharField(_("unique identifier"), max_length=64, unique=True),
-        depends=[("self", ["short_name"]), ("parent_location", ["unique_identifier"])],
+        depends=[("self", ["short_name"]),
+                 ("parent_location", ["unique_identifier"])],
     )
     def unique_identifier(self):
         if self.type.unique:
             return self.short_name
         return self.parent_location.unique_identifier + "." + self.short_name
 
     @computed(
-        models.CharField(_("locatable identifier"), max_length=512, unique=True),
+        models.CharField(_("locatable identifier"),
+                         max_length=512, unique=True),
         depends=[
             ("self", ["short_name"]),
             ("parent_location", ["locatable_identifier"]),
@@ -523,7 +552,7 @@ def get_absolute_url(self):
             "view_location",
             kwargs={"pk": self.pk, "unique_identifier": self.unique_identifier},
         )
-    
+
     def get_admin_url(self):
         return reverse(
             "admin:inventory_location_change",
@@ -536,7 +565,8 @@ class Meta:
         unique_together = ["item", "location"]
         order_with_respect_to = "location"
 
-    item = models.ForeignKey("Item", on_delete=models.CASCADE, verbose_name=_("item"))
+    item = models.ForeignKey(
+        "Item", on_delete=models.CASCADE, verbose_name=_("item"))
     location = models.ForeignKey(
         "Location", on_delete=models.CASCADE, verbose_name=_("location")
     )
@@ -566,6 +596,5 @@ def amount_text(self):
         else:
             return f"{self.amount_without_zeros} {self.item.measurement_unit.short}"
 
-
     def __str__(self):
         return f"{self.amount_text} @ {self.location.locatable_identifier}"

inventory/tasks.py

@@ -0,0 +1,13 @@
+import logging
+
+from celery import shared_task
+from django.apps import apps
+logger = logging.getLogger(__name__)
+
+
+@shared_task
+def run_ocr_on_item_image(pk):
+    logger.warning(f"Running OCR on image {pk}")
+    item_image = apps.get_model('inventory', 'ItemImage').objects.get(pk=pk)
+    item_image.run_ocr()
+    item_image.save_ocr_text()

requirements.txt

@@ -16,4 +16,6 @@ django-ipware
 django-bootstrap-icons
 tqdm
 pytesseract
+celery
+redis
 sorl-thumbnail

web-entrypoint.sh

@@ -3,4 +3,5 @@
 ./manage.py compilemessages
 ./manage.py collectstatic --noinput
 ./manage.py migrate
+./manage.py celery_worker run --background
 gunicorn imzam.wsgi -b 0.0.0.0:8000