Bypass de default models used by django_celery_beat.scheduler (#516)

when
`CELERY_BEAT_(?:PERIODICTASKS?|(?:CRONTAB|INTERVAL|SOLAR|CLOCKED)SCHEDULE)_MODEL`
constants are defined in django `settings`.

Providing the `app_label.model_name` of your own models as value for the
constants
`CELERY_BEAT_(?:PERIODICTASKS?|(?:CRONTAB|INTERVAL|SOLAR|CLOCKED)SCHEDULE)_MODEL`
will let `django_celery_beat.scheduler` use the custom models instead of
the default ones (aka generic models, in this context/pull-request):

```python
CELERY_BEAT_PERIODICTASK_MODEL = "app_label.model_name"
CELERY_BEAT_PERIODICTASKS_MODEL = "app_label.model_name"
CELERY_BEAT_CRONTABSCHEDULE_MODEL = "app_label.model_name"
CELERY_BEAT_INTERVALSCHEDULE_MODEL = "app_label.model_name"
CELERY_BEAT_SOLARSCHEDULE_MODEL = "app_label.model_name"
CELERY_BEAT_CLOCKEDSCHEDULE_MODEL = "app_label.model_name"
```

Doing this we add support to automatically bypass the default
`django_celery_beat` models without forcing developers to overwrite the
whole `django_celery_beat.scheduler` in projects where the default
models doesn't fit the requirements

I updated the `README.rst` with a small explanation about how this work

Additonal information:
* related issue: #516
* pull-request: #534

.gitignore

@@ -34,3 +34,4 @@ coverage.xml
 .python-version
 venv
 .env
+.vscode/

README.rst

@@ -86,6 +86,54 @@ manually:
         >>> from django_celery_beat.models import PeriodicTasks
         >>> PeriodicTasks.update_changed()
 
+Custom Models
+=============
+
+It's possible to use your own models instead of the default ones provided by ``django_celery_beat``, to do that just define your models inheriting from the right one from ``django_celery_beat.models.abstract``:
+
+.. code-block:: Python
+
+        # custom_app.models.py
+        from django_celery_beat.models.abstract import (
+            AbstractClockedSchedule,
+            AbstractCrontabSchedule,
+            AbstractIntervalSchedule,
+            AbstractPeriodicTask,
+            AbstractPeriodicTasks,
+            AbstractSolarSchedule,
+        )
+
+        class CustomPeriodicTask(AbstractPeriodicTask):
+            ...
+
+        class CustomPeriodicTasks(AbstractPeriodicTasks):
+            ...
+
+        class CustomCrontabSchedule(AbstractCrontabSchedule):
+            ...
+
+        class CustomIntervalSchedule(AbstractIntervalSchedule):
+            ...
+
+        class CustomSolarSchedule(AbstractSolarSchedule):
+            ...
+
+        class CustomClockedSchedule(AbstractClockedSchedule):
+            ...
+
+To let ``django_celery_beat.scheduler`` make use of your own modules, you must provide the ``app_name.model_name`` of your own custom models as values to the next constants in your settings:
+
+.. code-block:: Python
+
+        # settings.py
+        # CELERY_BEAT_(?:PERIODICTASKS?|(?:CRONTAB|INTERVAL|SOLAR|CLOCKED)SCHEDULE)_MODEL = "app_label.model_name"
+        CELERY_BEAT_PERIODICTASK_MODEL = "custom_app.CustomPeriodicTask"
+        CELERY_BEAT_PERIODICTASKS_MODEL = "custom_app.CustomPeriodicTasks"
+        CELERY_BEAT_CRONTABSCHEDULE_MODEL = "custom_app.CustomCrontabSchedule"
+        CELERY_BEAT_INTERVALSCHEDULE_MODEL = "custom_app.CustomIntervalSchedule"
+        CELERY_BEAT_SOLARSCHEDULE_MODEL = "custom_app.CustomSolarSchedule"
+        CELERY_BEAT_CLOCKEDSCHEDULE_MODEL = "custom_app.CustomClockedSchedule"
+
 Example creating interval-based periodic task
 ---------------------------------------------
 

django_celery_beat/helpers.py

@@ -0,0 +1,133 @@
+from django.apps import apps
+from django.conf import settings
+from django.core.exceptions import ImproperlyConfigured
+
+from .models import (
+    PeriodicTask, PeriodicTasks,
+    CrontabSchedule, IntervalSchedule,
+    SolarSchedule, ClockedSchedule
+)
+
+def crontabschedule_model():
+    """Return the CrontabSchedule model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_CRONTABSCHEDULE_MODEL'):
+        return CrontabSchedule
+
+    try:
+        return apps.get_model(
+            settings.CELERY_BEAT_CRONTABSCHEDULE_MODEL
+        )
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_CRONTABSCHEDULE_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_CRONTABSCHEDULE_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_CRONTABSCHEDULE_MODEL}' that has not "
+            "been installed"
+        )
+
+def intervalschedule_model():
+    """Return the IntervalSchedule model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_INTERVALSCHEDULE_MODEL'):
+        return IntervalSchedule
+
+    try:
+        return apps.get_model(
+            settings.CELERY_BEAT_INTERVALSCHEDULE_MODEL
+        )
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_INTERVALSCHEDULE_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_INTERVALSCHEDULE_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_INTERVALSCHEDULE_MODEL}' that has not "
+            "been installed"
+        )
+
+def periodictask_model():
+    """Return the PeriodicTask model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_PERIODICTASK_MODEL'):
+        return PeriodicTask
+
+    try:
+        return apps.get_model(settings.CELERY_BEAT_PERIODICTASK_MODEL)
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_PERIODICTASK_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_PERIODICTASK_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_PERIODICTASK_MODEL}' that has not been "
+            "installed"
+        )
+
+def periodictasks_model():
+    """Return the PeriodicTasks model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_PERIODICTASKS_MODEL'):
+        return PeriodicTasks
+
+    try:
+        return apps.get_model(
+            settings.CELERY_BEAT_PERIODICTASKS_MODEL
+        )
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_PERIODICTASKS_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_PERIODICTASKS_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_PERIODICTASKS_MODEL}' that has not been "
+            "installed"
+        )
+
+def solarschedule_model():
+    """Return the SolarSchedule model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_SOLARSCHEDULE_MODEL'):
+        return SolarSchedule
+
+    try:
+        return apps.get_model(
+            settings.CELERY_BEAT_SOLARSCHEDULE_MODEL
+        )
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_SOLARSCHEDULE_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_SOLARSCHEDULE_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_SOLARSCHEDULE_MODEL}' that has not been "
+            "installed"
+        )
+
+def clockedschedule_model():
+    """Return the ClockedSchedule model that is active in this project."""
+    if not hasattr(settings, 'CELERY_BEAT_CLOCKEDSCHEDULE_MODEL'):
+        return ClockedSchedule
+
+    try:
+        return apps.get_model(
+            settings.CELERY_BEAT_CLOCKEDSCHEDULE_MODEL
+        )
+    except ValueError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_CLOCKEDSCHEDULE_MODEL must be of the form "
+            "'app_label.model_name'"
+        )
+    except LookupError:
+        raise ImproperlyConfigured(
+            "CELERY_BEAT_CLOCKEDSCHEDULE_MODEL refers to model "
+            f"'{settings.CELERY_BEAT_CLOCKEDSCHEDULE_MODEL}' that has not "
+            "been installed"
+        )

django_celery_beat/schedulers.py

@@ -19,12 +19,15 @@
 from django.db.utils import DatabaseError, InterfaceError
 from django.core.exceptions import ObjectDoesNotExist
 
-from .models import (
-    PeriodicTask, PeriodicTasks,
-    CrontabSchedule, IntervalSchedule,
-    SolarSchedule, ClockedSchedule
-)
 from .clockedschedule import clocked
+from .helpers import (
+    clockedschedule_model,
+    crontabschedule_model,
+    intervalschedule_model,
+    periodictask_model,
+    periodictasks_model,
+    solarschedule_model,
+)
 from .utils import NEVER_CHECK_TIMEOUT
 
 # This scheduler must wake up more frequently than the
@@ -39,6 +42,13 @@
 logger = get_logger(__name__)
 debug, info, warning = logger.debug, logger.info, logger.warning
 
+ClockedSchedule = clockedschedule_model()
+CrontabSchedule = crontabschedule_model()
+IntervalSchedule = intervalschedule_model()
+PeriodicTask = periodictask_model()
+PeriodicTasks = periodictasks_model()
+SolarSchedule = solarschedule_model()
+
 
 class ModelEntry(ScheduleEntry):
     """Scheduler entry taken from database row."""