Celery signal processor implement (#414)

* Implement the Celery signal processor

The `CelerySignalProcessor` allows automatic updates on the index as delayed background tasks using Celery.

NB: We cannot process deletes as background tasks. By the time the Celery worker would pick up the delete job, the model instance would already deleted. We can get around this by setting Celery to use `pickle` and sending the object to the worker, but using `pickle` opens the application up to security concerns.

* Draft implementation for different signal processor tests

* requirements.txt update

* signal.py revert

revert signals.py

* update

* add delete task

* add delete and delete_related perpare

* fix import bug

* update documents and bug fixes.

* Celery signal processor branch bak (#2)

* add requiremnts deps
* add ci

* change optional require, update signal handle ways.

* change update task

* change update task

* change test case class.

---------

Co-authored-by: Rasika Amaratissa <[email protected]>
Co-authored-by: Andrii Rusanov <[email protected]>
Co-authored-by: bidaya0 <[email protected]>

Author: 4 people

.github/workflows/ci.yml

@@ -122,6 +122,7 @@ jobs:
         run: |
           TOX_ENV=$(echo "py${{ matrix.python-version }}-django-${{ matrix.django-version }}-es${{ matrix.es-dsl-version }}" | tr -d .)
           python -m tox -e $TOX_ENV -- --elasticsearch
+          python -m tox -e $TOX_ENV -- --elasticsearch --signal-processor celery
 
       - name: Publish Coverage Report
         uses: codecov/codecov-action@v1

django_elasticsearch_dsl/documents.py

@@ -219,6 +219,13 @@ def _get_actions(self, object_list, action):
         for object_instance in object_list:
             if action == 'delete' or self.should_index_object(object_instance):
                 yield self._prepare_action(object_instance, action)
+    
+    def get_actions(self, object_list, action):
+        """
+        Generate the elasticsearch payload.
+        """
+        return self._get_actions(object_list, action)
+
 
     def _bulk(self, *args, **kwargs):
         """Helper for switching between normal and parallel bulk operation"""

django_elasticsearch_dsl/registries.py

@@ -174,5 +174,11 @@ def get_indices(self, models=None):
 
         return set(iterkeys(self._indices))
 
+    def __contains__(self, model):
+        """
+        Checks that model is in registry
+        """
+        return model in self._models or model in self._related_models
+
 
 registry = DocumentRegistry()

django_elasticsearch_dsl/signals.py

@@ -7,10 +7,13 @@
 from __future__ import absolute_import
 
 from django.db import models
+from django.apps import apps
 from django.dispatch import Signal
-
 from .registries import registry
-
+from django.core.exceptions import ObjectDoesNotExist
+from importlib import import_module
+# Sent after document indexing is completed
+post_index = Signal()
 
 class BaseSignalProcessor(object):
     """Base signal processor.
@@ -96,6 +99,124 @@ def teardown(self):
         models.signals.m2m_changed.disconnect(self.handle_m2m_changed)
         models.signals.pre_delete.disconnect(self.handle_pre_delete)
 
+try:
+    from celery import shared_task
+except ImportError:
+    pass
+else:
+    class CelerySignalProcessor(RealTimeSignalProcessor):
+        """Celery signal processor.
+
+        Allows automatic updates on the index as delayed background tasks using
+        Celery.
+
+        NB: We cannot process deletes as background tasks.
+        By the time the Celery worker would pick up the delete job, the
+        model instance would already deleted. We can get around this by
+        setting Celery to use `pickle` and sending the object to the worker,
+        but using `pickle` opens the application up to security concerns.
+        """
 
-# Sent after document indexing is completed
-post_index = Signal()
+        def handle_save(self, sender, instance, **kwargs):
+            """Handle save with a Celery task.
+
+            Given an individual model instance, update the object in the index.
+            Update the related objects either.
+            """
+            pk = instance.pk
+            app_label = instance._meta.app_label
+            model_name = instance.__class__.__name__
+
+            self.registry_update_task.delay(pk, app_label, model_name)
+            self.registry_update_related_task.delay(pk, app_label, model_name)
+
+        def handle_pre_delete(self, sender, instance, **kwargs):
+            """Handle removing of instance object from related models instance.
+            We need to do this before the real delete otherwise the relation
+            doesn't exists anymore and we can't get the related models instance.
+            """
+            self.prepare_registry_delete_related_task(instance)
+
+        def handle_delete(self, sender, instance, **kwargs):
+            """Handle delete.
+
+            Given an individual model instance, delete the object from index.
+            """
+            self.prepare_registry_delete_task(instance)
+
+        def prepare_registry_delete_related_task(self, instance):
+            """
+            Select its related instance before this instance was deleted.
+            And pass that to celery.
+            """
+            action = 'index'
+            for doc in registry._get_related_doc(instance):
+                doc_instance = doc(related_instance_to_ignore=instance)
+                try:
+                    related = doc_instance.get_instances_from_related(instance)
+                except ObjectDoesNotExist:
+                    related = None
+                if related is not None:
+                    doc_instance.update(related)
+                    if isinstance(related, models.Model):
+                        object_list = [related]
+                    else:
+                        object_list = related
+                    bulk_data = list(doc_instance._get_actions(object_list, action)),
+                    self.registry_delete_task.delay(doc_instance.__class__.__name__, bulk_data)
+
+        @shared_task()
+        def registry_delete_task(doc_label, data):
+            """
+            Handle the bulk delete data on the registry as a Celery task.
+            The different implementations used are due to the difference between delete and update operations. 
+            The update operation can re-read the updated data from the database to ensure eventual consistency, 
+            but the delete needs to be processed before the database record is deleted to obtain the associated data.
+            """
+            doc_instance = import_module(doc_label)
+            parallel = True
+            doc_instance._bulk(bulk_data, parallel=parallel)
+
+        def prepare_registry_delete_task(self, instance):
+            """
+            Get the prepare did before database record deleted.
+            """
+            action = 'delete'
+            for doc in registry._get_related_doc(instance):
+                doc_instance = doc(related_instance_to_ignore=instance)
+                try:
+                    related = doc_instance.get_instances_from_related(instance)
+                except ObjectDoesNotExist:
+                    related = None
+                if related is not None:
+                    doc_instance.update(related)
+                    if isinstance(related, models.Model):
+                        object_list = [related]
+                    else:
+                        object_list = related
+                    bulk_data = list(doc_instance.get_actions(object_list, action)),
+                    self.registry_delete_task.delay(doc_instance.__class__.__name__, bulk_data)
+
+        @shared_task()
+        def registry_update_task(pk, app_label, model_name):
+            """Handle the update on the registry as a Celery task."""
+            try:
+                model = apps.get_model(app_label, model_name)
+            except LookupError:
+                pass
+            else:
+                registry.update(
+                    model.objects.get(pk=pk)
+                )
+
+        @shared_task()
+        def registry_update_related_task(pk, app_label, model_name):
+            """Handle the related update on the registry as a Celery task."""
+            try:
+                model = apps.get_model(app_label, model_name)
+            except LookupError:
+                pass
+            else:
+                registry.update_related(
+                    model.objects.get(pk=pk)
+                )

docs/source/settings.rst

@@ -37,8 +37,15 @@ An example:
 
 Defaults to ``django_elasticsearch_dsl.signals.RealTimeSignalProcessor``.
 
-You could, for instance, make a ``CelerySignalProcessor`` which would add
-update jobs to the queue to for delayed processing.
+Options: ``django_elasticsearch_dsl.signals.RealTimeSignalProcessor`` \ ``django_elasticsearch_dsl.signals.CelerySignalProcessor``
+
+In this ``CelerySignalProcessor`` implementation,
+Create and update operations will record the updated data primary key from the database and delay the time to find the association to ensure eventual consistency.
+Delete operations are processed to obtain associated data before database records are deleted.
+And celery needs to be pre-configured in the django project, for example  `Using Celery with Django <https://docs.celeryq.dev/en/stable/django/first-steps-with-django.html>`.
+
+You could, for instance, make a ``CustomSignalProcessor`` which would apply
+update jobs as your wish.
 
 ELASTICSEARCH_DSL_PARALLEL
 ==========================

requirements.txt

@@ -1,3 +1,2 @@
 django>=1.9.6
 elasticsearch-dsl>=7.0.0,<8.0.0
-

requirements_test.txt

@@ -3,6 +3,7 @@ mock>=1.0.1
 flake8>=2.1.0
 tox>=1.7.0
 Pillow==6.2.0
+celery>=4.1.0
 
 
 # Additional test requirements go here

runtests.py

@@ -2,11 +2,19 @@
 import sys
 import argparse
 
+from celery import Celery
+
 try:
     from django.conf import settings
     from django.test.utils import get_runner
 
-    def get_settings():
+    def get_settings(signal_processor):
+        PROCESSOR_CLASSES = {
+            'realtime': 'django_elasticsearch_dsl.signals.RealTimeSignalProcessor',
+            'celery': 'django_elasticsearch_dsl.signals.CelerySignalProcessor',
+        }
+
+        signal_processor = PROCESSOR_CLASSES[signal_processor]
         settings.configure(
             DEBUG=True,
             USE_TZ=True,
@@ -31,6 +39,10 @@ def get_settings():
                 },
             },
             DEFAULT_AUTO_FIELD="django.db.models.BigAutoField",
+            CELERY_BROKER_URL='memory://localhost/',
+            CELERY_TASK_ALWAYS_EAGER=True,
+            CELERY_EAGER_PROPAGATES_EXCEPTIONS=True,
+            ELASTICSEARCH_DSL_SIGNAL_PROCESSOR=signal_processor
         )
 
         try:
@@ -41,6 +53,9 @@ def get_settings():
         else:
             setup()
 
+        app = Celery()
+        app.config_from_object('django.conf:settings', namespace='CELERY')
+        app.autodiscover_tasks(lambda: settings.INSTALLED_APPS)
         return settings
 
 except ImportError:
@@ -59,6 +74,13 @@ def make_parser():
         const='localhost:9200',
         help="To run integration test against an Elasticsearch server",
     )
+    parser.add_argument(
+        '--signal-processor',
+        nargs='?',
+        default='realtime',
+        choices=('realtime', 'celery'),
+        help='Defines which signal backend to choose'
+    )
     return parser
 
 
@@ -70,7 +92,9 @@ def run_tests(*test_args):
     if not test_args:
         test_args = ['tests']
 
-    settings = get_settings()
+    signal_processor = args.signal_processor
+
+    settings = get_settings(signal_processor)
     TestRunner = get_runner(settings)
     test_runner = TestRunner()
 

setup.py

@@ -72,4 +72,7 @@
         'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.10',
     ],
+    extras_require={
+        'celery':  ["celery>=4.1.0"],
+    }
 )

tests/test_documents.py

@@ -1,5 +1,7 @@
 import json
 from unittest import TestCase
+from unittest import SkipTest
+
 
 import django
 from django.db import models
@@ -64,7 +66,19 @@ class Index:
         doc_type = 'car_document'
 
 
-class DocTypeTestCase(TestCase):
+class BaseDocTypeTestCase(object):
+    TARGET_PROCESSOR = None
+
+    @classmethod
+    def setUpClass(cls):
+        from django.conf import settings
+        if cls.TARGET_PROCESSOR != settings.ELASTICSEARCH_DSL_SIGNAL_PROCESSOR:
+            raise SkipTest(
+                "Skipped because {} is required, not {}".format(
+                    cls.TARGET_PROCESSOR, settings.ELASTICSEARCH_DSL_SIGNAL_PROCESSOR
+                )
+            )
+        super(BaseDocTypeTestCase,cls).setUpClass()
 
     def test_model_class_added(self):
         self.assertEqual(CarDocument.django.model, Car)
@@ -538,3 +552,10 @@ def should_index_object(self, obj):
         data_body = mock_bulk.call_args[1]['body']
         self.assertTrue(article1.slug in data_body)
         self.assertTrue(article2.slug not in data_body)
+
+class RealTimeDocTypeTestCase(BaseDocTypeTestCase, TestCase):
+    TARGET_PROCESSOR = 'django_elasticsearch_dsl.signals.RealTimeSignalProcessor'
+
+
+class CeleryDocTypeTestCase(BaseDocTypeTestCase, TestCase):
+    TARGET_PROCESSOR = 'django_elasticsearch_dsl.signals.CelerySignalProcessor'