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"""The module which provides a way to nest your DAGs and so your levels of complexity."""
from enum import Enum
from typing import Dict, Optional
from sqlalchemy.orm.session import Session
from airflow.api.common.experimental.get_task_instance import get_task_instance
from airflow.exceptions import AirflowException, TaskInstanceNotFound
from airflow.models import DagRun
from airflow.models.dag import DAG, DagContext
from airflow.models.pool import Pool
from airflow.models.taskinstance import TaskInstance
from airflow.sensors.base import BaseSensorOperator
from airflow.utils.session import create_session, provide_session
from airflow.utils.state import State
from airflow.utils.types import DagRunType
[docs]class SkippedStatePropagationOptions(Enum):
"""Available options for skipped state propagation of subdag's tasks to parent dag tasks."""
[docs] ALL_LEAVES = 'all_leaves'
[docs]class SubDagOperator(BaseSensorOperator):
"""
This runs a sub dag. By convention, a sub dag's dag_id
should be prefixed by its parent and a dot. As in `parent.child`.
Although SubDagOperator can occupy a pool/concurrency slot,
user can specify the mode=reschedule so that the slot will be
released periodically to avoid potential deadlock.
:param subdag: the DAG object to run as a subdag of the current DAG.
:param session: sqlalchemy session
:param conf: Configuration for the subdag
:type conf: dict
:param propagate_skipped_state: by setting this argument you can define
whether the skipped state of leaf task(s) should be propagated to the
parent dag's downstream task.
"""
@provide_session
def __init__(
self,
*,
subdag: DAG,
session: Optional[Session] = None,
conf: Optional[Dict] = None,
propagate_skipped_state: Optional[SkippedStatePropagationOptions] = None,
**kwargs,
) -> None:
super().__init__(**kwargs)
self.subdag = subdag
self.conf = conf
self.propagate_skipped_state = propagate_skipped_state
self._validate_dag(kwargs)
self._validate_pool(session)
[docs] def _validate_dag(self, kwargs):
dag = kwargs.get('dag') or DagContext.get_current_dag()
if not dag:
raise AirflowException('Please pass in the `dag` param or call within a DAG context manager')
if dag.dag_id + '.' + kwargs['task_id'] != self.subdag.dag_id:
raise AirflowException(
"The subdag's dag_id should have the form '{{parent_dag_id}}.{{this_task_id}}'. "
"Expected '{d}.{t}'; received '{rcvd}'.".format(
d=dag.dag_id, t=kwargs['task_id'], rcvd=self.subdag.dag_id
)
)
[docs] def _validate_pool(self, session):
if self.pool:
conflicts = [t for t in self.subdag.tasks if t.pool == self.pool]
if conflicts:
# only query for pool conflicts if one may exist
pool = session.query(Pool).filter(Pool.slots == 1).filter(Pool.pool == self.pool).first()
if pool and any(t.pool == self.pool for t in self.subdag.tasks):
raise AirflowException(
'SubDagOperator {sd} and subdag task{plural} {t} both '
'use pool {p}, but the pool only has 1 slot. The '
'subdag tasks will never run.'.format(
sd=self.task_id,
plural=len(conflicts) > 1,
t=', '.join(t.task_id for t in conflicts),
p=self.pool,
)
)
[docs] def _get_dagrun(self, execution_date):
dag_runs = DagRun.find(
dag_id=self.subdag.dag_id,
execution_date=execution_date,
)
return dag_runs[0] if dag_runs else None
[docs] def _reset_dag_run_and_task_instances(self, dag_run, execution_date):
"""
Set the DagRun state to RUNNING and set the failed TaskInstances to None state
for scheduler to pick up.
:param dag_run: DAG run
:param execution_date: Execution date
:return: None
"""
with create_session() as session:
dag_run.state = State.RUNNING
session.merge(dag_run)
failed_task_instances = (
session.query(TaskInstance)
.filter(TaskInstance.dag_id == self.subdag.dag_id)
.filter(TaskInstance.execution_date == execution_date)
.filter(TaskInstance.state.in_([State.FAILED, State.UPSTREAM_FAILED]))
)
for task_instance in failed_task_instances:
task_instance.state = State.NONE
session.merge(task_instance)
session.commit()
[docs] def pre_execute(self, context):
execution_date = context['execution_date']
dag_run = self._get_dagrun(execution_date)
if dag_run is None:
dag_run = self.subdag.create_dagrun(
run_type=DagRunType.SCHEDULED,
execution_date=execution_date,
state=State.RUNNING,
conf=self.conf,
external_trigger=True,
)
self.log.info("Created DagRun: %s", dag_run.run_id)
else:
self.log.info("Found existing DagRun: %s", dag_run.run_id)
if dag_run.state == State.FAILED:
self._reset_dag_run_and_task_instances(dag_run, execution_date)
[docs] def poke(self, context):
execution_date = context['execution_date']
dag_run = self._get_dagrun(execution_date=execution_date)
return dag_run.state != State.RUNNING
[docs] def post_execute(self, context, result=None):
execution_date = context['execution_date']
dag_run = self._get_dagrun(execution_date=execution_date)
self.log.info("Execution finished. State is %s", dag_run.state)
if dag_run.state != State.SUCCESS:
raise AirflowException(f"Expected state: SUCCESS. Actual state: {dag_run.state}")
if self.propagate_skipped_state and self._check_skipped_states(context):
self._skip_downstream_tasks(context)
[docs] def _check_skipped_states(self, context):
leaves_tis = self._get_leaves_tis(context['execution_date'])
if self.propagate_skipped_state == SkippedStatePropagationOptions.ANY_LEAF:
return any(ti.state == State.SKIPPED for ti in leaves_tis)
if self.propagate_skipped_state == SkippedStatePropagationOptions.ALL_LEAVES:
return all(ti.state == State.SKIPPED for ti in leaves_tis)
raise AirflowException(
f'Unimplemented SkippedStatePropagationOptions {self.propagate_skipped_state} used.'
)
[docs] def _get_leaves_tis(self, execution_date):
leaves_tis = []
for leaf in self.subdag.leaves:
try:
ti = get_task_instance(
dag_id=self.subdag.dag_id, task_id=leaf.task_id, execution_date=execution_date
)
leaves_tis.append(ti)
except TaskInstanceNotFound:
continue
return leaves_tis
[docs] def _skip_downstream_tasks(self, context):
self.log.info(
'Skipping downstream tasks because propagate_skipped_state is set to %s '
'and skipped task(s) were found.',
self.propagate_skipped_state,
)
downstream_tasks = context['task'].downstream_list
self.log.debug('Downstream task_ids %s', downstream_tasks)
if downstream_tasks:
self.skip(context['dag_run'], context['execution_date'], downstream_tasks)
self.log.info('Done.')