# -*- coding: utf-8 -*-
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from time import sleep
from datetime import timedelta
from airflow.exceptions import AirflowException, AirflowSensorTimeout, \
AirflowSkipException, AirflowRescheduleException
from airflow.models import BaseOperator, SkipMixin, TaskReschedule
from airflow.utils import timezone
from airflow.utils.decorators import apply_defaults
from airflow.ti_deps.deps.ready_to_reschedule import ReadyToRescheduleDep
[docs]class BaseSensorOperator(BaseOperator, SkipMixin):
"""
Sensor operators are derived from this class and inherit these attributes.
Sensor operators keep executing at a time interval and succeed when
a criteria is met and fail if and when they time out.
:param soft_fail: Set to true to mark the task as SKIPPED on failure
:type soft_fail: bool
:param poke_interval: Time in seconds that the job should wait in
between each tries
:type poke_interval: int
:param timeout: Time, in seconds before the task times out and fails.
:type timeout: int
:param mode: How the sensor operates.
Options are: ``{ poke | reschedule }``, default is ``poke``.
When set to ``poke`` the sensor is taking up a worker slot for its
whole execution time and sleeps between pokes. Use this mode if the
expected runtime of the sensor is short or if a short poke interval
is required. Note that the sensor will hold onto a worker slot and
a pool slot for the duration of the sensor's runtime in this mode.
When set to ``reschedule`` the sensor task frees the worker slot when
the criteria is not yet met and it's rescheduled at a later time. Use
this mode if the time before the criteria is met is expected to be
quite long. The poke interval should be more than one minute to
prevent too much load on the scheduler.
:type mode: str
"""
[docs] valid_modes = ['poke', 'reschedule']
@apply_defaults
def __init__(self,
poke_interval=60,
timeout=60 * 60 * 24 * 7,
soft_fail=False,
mode='poke',
*args,
**kwargs):
super(BaseSensorOperator, self).__init__(*args, **kwargs)
self.poke_interval = poke_interval
self.soft_fail = soft_fail
self.timeout = timeout
self.mode = mode
self._validate_input_values()
[docs] def poke(self, context):
"""
Function that the sensors defined while deriving this class should
override.
"""
raise AirflowException('Override me.')
[docs] def execute(self, context):
started_at = timezone.utcnow()
if self.reschedule:
# If reschedule, use first start date of current try
task_reschedules = TaskReschedule.find_for_task_instance(context['ti'])
if task_reschedules:
started_at = task_reschedules[0].start_date
while not self.poke(context):
if (timezone.utcnow() - started_at).total_seconds() > self.timeout:
# If sensor is in soft fail mode but will be retried then
# give it a chance and fail with timeout.
# This gives the ability to set up non-blocking AND soft-fail sensors.
if self.soft_fail and not context['ti'].is_eligible_to_retry():
self._do_skip_downstream_tasks(context)
raise AirflowSkipException('Snap. Time is OUT.')
else:
raise AirflowSensorTimeout('Snap. Time is OUT.')
if self.reschedule:
reschedule_date = timezone.utcnow() + timedelta(
seconds=self.poke_interval)
raise AirflowRescheduleException(reschedule_date)
else:
sleep(self.poke_interval)
self.log.info("Success criteria met. Exiting.")
[docs] def _do_skip_downstream_tasks(self, context):
downstream_tasks = context['task'].get_flat_relatives(upstream=False)
self.log.debug("Downstream task_ids %s", downstream_tasks)
if downstream_tasks:
self.skip(context['dag_run'], context['ti'].execution_date, downstream_tasks)
@property
[docs] def reschedule(self):
return self.mode == 'reschedule'
@property
[docs] def deps(self):
"""
Adds one additional dependency for all sensor operators that
checks if a sensor task instance can be rescheduled.
"""
return BaseOperator.deps.fget(self) | {ReadyToRescheduleDep()}