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# to you under the Apache License, Version 2.0 (the
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# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing,
# software distributed under the License is distributed on an
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# KIND, either express or implied. See the License for the
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# under the License.
import warnings
from abc import ABCMeta, abstractmethod
from typing import TYPE_CHECKING, Any, Iterable, Iterator, List, Optional, Sequence, Set, Tuple, Union
import pendulum
from airflow.exceptions import AirflowException
from airflow.serialization.enums import DagAttributeTypes
if TYPE_CHECKING:
from logging import Logger
from airflow.models.dag import DAG
from airflow.models.mappedoperator import MappedOperator
from airflow.utils.edgemodifier import EdgeModifier
from airflow.utils.task_group import TaskGroup
[docs]class DependencyMixin:
"""Mixing implementing common dependency setting methods methods like >> and <<."""
@property
[docs] def roots(self) -> Sequence["DependencyMixin"]:
"""
List of root nodes -- ones with no upstream dependencies.
a.k.a. the "start" of this sub-graph
"""
raise NotImplementedError()
@property
[docs] def leaves(self) -> Sequence["DependencyMixin"]:
"""
List of leaf nodes -- ones with only upstream dependencies.
a.k.a. the "end" of this sub-graph
"""
raise NotImplementedError()
@abstractmethod
[docs] def set_upstream(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Set a task or a task list to be directly upstream from the current task."""
raise NotImplementedError()
@abstractmethod
[docs] def set_downstream(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Set a task or a task list to be directly downstream from the current task."""
raise NotImplementedError()
[docs] def update_relative(self, other: "DependencyMixin", upstream=True) -> None:
"""
Update relationship information about another TaskMixin. Default is no-op.
Override if necessary.
"""
[docs] def __lshift__(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Implements Task << Task"""
self.set_upstream(other)
return other
[docs] def __rshift__(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Implements Task >> Task"""
self.set_downstream(other)
return other
[docs] def __rrshift__(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Called for Task >> [Task] because list don't have __rshift__ operators."""
self.__lshift__(other)
return self
[docs] def __rlshift__(self, other: Union["DependencyMixin", Sequence["DependencyMixin"]]):
"""Called for Task << [Task] because list don't have __lshift__ operators."""
self.__rshift__(other)
return self
[docs]class TaskMixin(DependencyMixin):
""":meta private:"""
[docs] def __init_subclass__(cls) -> None:
warnings.warn(
f"TaskMixin has been renamed to DependencyMixin, please update {cls.__name__}",
category=DeprecationWarning,
stacklevel=2,
)
return super().__init_subclass__()
[docs]class DAGNode(DependencyMixin, metaclass=ABCMeta):
"""
A base class for a node in the graph of a workflow -- an Operator or a Task Group, either mapped or
unmapped.
"""
[docs] dag: Optional["DAG"] = None
[docs] task_group: Optional["TaskGroup"] = None
"""The task_group that contains this node"""
@property
@abstractmethod
[docs] def node_id(self) -> str:
raise NotImplementedError()
@property
[docs] def label(self) -> Optional[str]:
tg = self.task_group
if tg and tg.node_id and tg.prefix_group_id:
# "task_group_id.task_id" -> "task_id"
return self.node_id[len(tg.node_id) + 1 :]
return self.node_id
[docs] start_date: Optional[pendulum.DateTime]
[docs] end_date: Optional[pendulum.DateTime]
[docs] upstream_task_ids: Set[str]
[docs] downstream_task_ids: Set[str]
[docs] def has_dag(self) -> bool:
return self.dag is not None
@property
[docs] def dag_id(self) -> str:
"""Returns dag id if it has one or an adhoc/meaningless ID"""
if self.dag:
return self.dag.dag_id
return "_in_memory_dag_"
@property
[docs] def log(self) -> "Logger":
raise NotImplementedError()
@property
@abstractmethod
[docs] def roots(self) -> Sequence["DAGNode"]:
raise NotImplementedError()
@property
@abstractmethod
[docs] def leaves(self) -> Sequence["DAGNode"]:
raise NotImplementedError()
def _set_relatives(
self,
task_or_task_list: Union[DependencyMixin, Sequence[DependencyMixin]],
upstream: bool = False,
edge_modifier: Optional["EdgeModifier"] = None,
) -> None:
"""Sets relatives for the task or task list."""
from airflow.models.baseoperator import BaseOperator
from airflow.models.mappedoperator import MappedOperator
from airflow.models.operator import Operator
if not isinstance(task_or_task_list, Sequence):
task_or_task_list = [task_or_task_list]
task_list: List[Operator] = []
for task_object in task_or_task_list:
task_object.update_relative(self, not upstream)
relatives = task_object.leaves if upstream else task_object.roots
for task in relatives:
if not isinstance(task, (BaseOperator, MappedOperator)):
raise AirflowException(
f"Relationships can only be set between Operators; received {task.__class__.__name__}"
)
task_list.append(task)
# relationships can only be set if the tasks share a single DAG. Tasks
# without a DAG are assigned to that DAG.
dags: Set["DAG"] = {task.dag for task in [*self.roots, *task_list] if task.has_dag() and task.dag}
if len(dags) > 1:
raise AirflowException(f'Tried to set relationships between tasks in more than one DAG: {dags}')
elif len(dags) == 1:
dag = dags.pop()
else:
raise AirflowException(
f"Tried to create relationships between tasks that don't have DAGs yet. "
f"Set the DAG for at least one task and try again: {[self, *task_list]}"
)
if not self.has_dag():
# If this task does not yet have a dag, add it to the same dag as the other task.
self.dag = dag
def add_only_new(obj, item_set: Set[str], item: str) -> None:
"""Adds only new items to item set"""
if item in item_set:
self.log.warning('Dependency %s, %s already registered for DAG: %s', obj, item, dag.dag_id)
else:
item_set.add(item)
for task in task_list:
if dag and not task.has_dag():
# If the other task does not yet have a dag, add it to the same dag as this task and
dag.add_task(task)
if upstream:
add_only_new(task, task.downstream_task_ids, self.node_id)
add_only_new(self, self.upstream_task_ids, task.node_id)
if edge_modifier:
edge_modifier.add_edge_info(self.dag, task.node_id, self.node_id)
else:
add_only_new(self, self.downstream_task_ids, task.node_id)
add_only_new(task, task.upstream_task_ids, self.node_id)
if edge_modifier:
edge_modifier.add_edge_info(self.dag, self.node_id, task.node_id)
[docs] def set_downstream(
self,
task_or_task_list: Union[DependencyMixin, Sequence[DependencyMixin]],
edge_modifier: Optional["EdgeModifier"] = None,
) -> None:
"""Set a node (or nodes) to be directly downstream from the current node."""
self._set_relatives(task_or_task_list, upstream=False, edge_modifier=edge_modifier)
[docs] def set_upstream(
self,
task_or_task_list: Union[DependencyMixin, Sequence[DependencyMixin]],
edge_modifier: Optional["EdgeModifier"] = None,
) -> None:
"""Set a node (or nodes) to be directly upstream from the current node."""
self._set_relatives(task_or_task_list, upstream=True, edge_modifier=edge_modifier)
@property
[docs] def downstream_list(self) -> Iterable["DAGNode"]:
"""List of nodes directly downstream"""
if not self.dag:
raise AirflowException(f'Operator {self} has not been assigned to a DAG yet')
return [self.dag.get_task(tid) for tid in self.downstream_task_ids]
@property
[docs] def upstream_list(self) -> Iterable["DAGNode"]:
"""List of nodes directly upstream"""
if not self.dag:
raise AirflowException(f'Operator {self} has not been assigned to a DAG yet')
return [self.dag.get_task(tid) for tid in self.upstream_task_ids]
[docs] def get_direct_relative_ids(self, upstream: bool = False) -> Set[str]:
"""
Get set of the direct relative ids to the current task, upstream or
downstream.
"""
if upstream:
return self.upstream_task_ids
else:
return self.downstream_task_ids
[docs] def get_direct_relatives(self, upstream: bool = False) -> Iterable["DAGNode"]:
"""
Get list of the direct relatives to the current task, upstream or
downstream.
"""
if upstream:
return self.upstream_list
else:
return self.downstream_list
[docs] def serialize_for_task_group(self) -> Tuple[DagAttributeTypes, Any]:
"""This is used by SerializedTaskGroup to serialize a task group's content."""
raise NotImplementedError()
def _iter_all_mapped_downstreams(self) -> Iterator["MappedOperator"]:
"""Return mapped nodes that are direct dependencies of the current task.
For now, this walks the entire DAG to find mapped nodes that has this
current task as an upstream. We cannot use ``downstream_list`` since it
only contains operators, not task groups. In the future, we should
provide a way to record an DAG node's all downstream nodes instead.
Note that this does not guarantee the returned tasks actually use the
current task for task mapping, but only checks those task are mapped
operators, and are downstreams of the current task.
To get a list of tasks that uses the current task for task mapping, use
:meth:`iter_mapped_dependants` instead.
"""
from airflow.models.mappedoperator import MappedOperator
from airflow.utils.task_group import TaskGroup
def _walk_group(group: TaskGroup) -> Iterable[Tuple[str, DAGNode]]:
"""Recursively walk children in a task group.
This yields all direct children (including both tasks and task
groups), and all children of any task groups.
"""
for key, child in group.children.items():
yield key, child
if isinstance(child, TaskGroup):
yield from _walk_group(child)
tg = self.task_group
if not tg:
raise RuntimeError("Cannot check for mapped dependants when not attached to a DAG")
for key, child in _walk_group(tg):
if key == self.node_id:
continue
if not isinstance(child, MappedOperator):
continue
if self.node_id in child.upstream_task_ids:
yield child
[docs] def iter_mapped_dependants(self) -> Iterator["MappedOperator"]:
"""Return mapped nodes that depend on the current task the expansion.
For now, this walks the entire DAG to find mapped nodes that has this
current task as an upstream. We cannot use ``downstream_list`` since it
only contains operators, not task groups. In the future, we should
provide a way to record an DAG node's all downstream nodes instead.
"""
return (
downstream
for downstream in self._iter_all_mapped_downstreams()
if any(p.node_id == self.node_id for p in downstream.iter_mapped_dependencies())
)
