Celery distributed task queue module for Invenio.

Invenio-Celery is a small discovery layer that takes care of discovering and loading tasks from other Invenio modules, as well as providing configuration defaults for Celery usage in Invenio. Invenio-Celery relies on Flask-CeleryExt for integrating Flask and Celery with application factories.

Defining tasks

Invenio modules that wish to define Celery tasks should use the @shared_task decorator (usually in

# mymodule/
from celery import shared_task

def sum(x, y):
     return x + y

Additionally the Invenio module should add the task module into the invenio_celery.tasks entry point:

    # ...
        'invenio_celery.tasks' : [
            'mymodule = mymodule.tasks'

Using tasks

Invenio modules that need to call tasks do not need to do anything special as long as the Invenio-Celery extension has been initialized. Hence calling tasks is as simple as:

from mymoudle.tasks import sum
result = sum.delay(2, 2)

Periodic tasks

Periodic tasks can be configured via CELERYBEAT_SCHEDULE configuration variable:

    'indexer': {
        'task': 'invenio_indexer.tasks.process_bulk_queue',
        'schedule': timedelta(minutes=5),

For further information about see Periodic Tasks chapter of the Celery documentation.

Celery workers

Invenio-Celery hooks into the Celery application loading process so that when a worker starts, all the tasks modules defined in invenio_celery.tasks will be imported and cause the tasks to be registered in the worker. Note that this only happens on the Celery worker side which needs to know upfront all the possible tasks.

For further details on how to setup Celery and define an Celery application factory please see Flask-CeleryExt