Source code for airflow.providers.celery.sensors.celery_queue

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from typing import TYPE_CHECKING, Optional

from celery.app import control

from airflow.sensors.base import BaseSensorOperator

if TYPE_CHECKING:
    from airflow.utils.context import Context


[docs]class CeleryQueueSensor(BaseSensorOperator):
    """
    Waits for a Celery queue to be empty. By default, in order to be considered
    empty, the queue must not have any tasks in the ``reserved``, ``scheduled``
    or ``active`` states.

    :param celery_queue: The name of the Celery queue to wait for.
    :param target_task_id: Task id for checking
    """

    def __init__(self, *, celery_queue: str, target_task_id: Optional[str] = None, **kwargs) -> None:

        super().__init__(**kwargs)
        self.celery_queue = celery_queue
        self.target_task_id = target_task_id

    def _check_task_id(self, context: 'Context') -> bool:
        """
        Gets the returned Celery result from the Airflow task
        ID provided to the sensor, and returns True if the
        celery result has been finished execution.

        :param context: Airflow's execution context
        :return: True if task has been executed, otherwise False
        :rtype: bool
        """
        ti = context['ti']
        celery_result = ti.xcom_pull(task_ids=self.target_task_id)
        return celery_result.ready()

[docs]    def poke(self, context: 'Context') -> bool:

        if self.target_task_id:
            return self._check_task_id(context)

        inspect_result = control.Inspect()
        reserved = inspect_result.reserved()
        scheduled = inspect_result.scheduled()
        active = inspect_result.active()

        try:
            reserved = len(reserved[self.celery_queue])
            scheduled = len(scheduled[self.celery_queue])
            active = len(active[self.celery_queue])

            self.log.info('Checking if celery queue %s is empty.', self.celery_queue)

            return reserved == 0 and scheduled == 0 and active == 0
        except KeyError:
            raise KeyError(f'Could not locate Celery queue {self.celery_queue}')