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Posted to commits@airflow.apache.org by GitBox <gi...@apache.org> on 2020/08/12 00:38:19 UTC
[GitHub] [airflow] houqp commented on a change in pull request #10153: [AIP-34] Alternative proposal: Add TaskGroup as a DAG construction helper and UI concept with example
houqp commented on a change in pull request #10153:
URL: https://github.com/apache/airflow/pull/10153#discussion_r468937005
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File path: airflow/utils/task_group.py
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@@ -0,0 +1,233 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# 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
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""
+TaskGroup
+"""
+
+from typing import List, Optional
+
+
+class TaskGroup:
+ """
+ A collection of tasks. Tasks within the TaskGroup have their task_id prefixed with the
+ group_id of the TaskGroup. When set_downstream() or set_upstream() are called on the
+ TaskGroup, it is applied across all tasks within the group if necessary.
+ """
+ def __init__(self, group_id, parent_group=None):
+ if group_id is None:
+ # This creates a root TaskGroup.
+ self.parent_group = None
+ else:
+ if not isinstance(group_id, str):
+ raise ValueError("group_id must be str")
+ if not group_id:
+ raise ValueError("group_id must not be empty")
+ self.parent_group = parent_group or TaskGroupContext.get_current_task_group()
+
+ self._group_id = group_id
+ if self.parent_group:
+ self.parent_group.add(self)
+ self.children = {}
+
+ @classmethod
+ def create_root(cls):
+ """
+ Create a root TaskGroup with no group_id or parent.
+ """
+ return cls(group_id=None)
+
+ @property
+ def is_root(self):
+ """
+ Returns True if this TaskGroup is the root TaskGroup. Otherwise False
+ """
+ return not self.parent_group
+
+ def __iter__(self):
+ for child in self.children.values():
+ if isinstance(child, TaskGroup):
+ for inner_task in child:
+ yield inner_task
+ else:
+ yield child
+
+ def add(self, task):
+ """
+ Add a task to this TaskGroup.
+ """
+ if task.label in self.children:
+ raise ValueError(f"Duplicate label {task.label} in {self.group_id}")
+ self.children[task.label] = task
+
+ @property
+ def label(self):
+ """
+ group_id excluding parent's group_id.
+ """
+ return self._group_id
+
+ @property
+ def group_id(self):
+ """
+ group_id is prefixed with parent group_id if applicable.
+ """
+ if not self.group_ids:
+ return None
+
+ return ".".join(self.group_ids)
+
+ @property
+ def group_ids(self):
+ """
+ Returns all the group_id of nested TaskGroups as a list, starting from the top.
+ """
+ return list(self._group_ids())[1:]
+
+ def _group_ids(self):
+ if self.parent_group:
+ for group_id in self.parent_group._group_ids(): # pylint: disable=protected-access
+ yield group_id
+
+ yield self._group_id
+
+ def set_downstream(self, task_or_task_list) -> None:
+ """
+ Call set_downstream for all leaf tasks within this TaskGroup.
+ """
+ for task in self.get_leaves():
+ task.set_downstream(task_or_task_list)
+
+ def set_upstream(self, task_or_task_list) -> None:
+ """
+ Call set_upstream for all root tasks within this TaskGroup.
+ """
+ for task in self.get_roots():
+ task.set_upstream(task_or_task_list)
+
+ def __enter__(self):
+ TaskGroupContext.push_context_managed_task_group(self)
+ return self
+
+ def __exit__(self, _type, _value, _tb):
+ TaskGroupContext.pop_context_managed_task_group()
+
+ def get_roots(self):
+ """
+ Returns a generator of tasks that are root tasks, i.e. those with no upstream
+ dependencies within the TaskGroup.
+ """
+ for task in self:
+ if not any(parent.is_in_task_group(self.group_ids)
+ for parent in task.get_direct_relatives(upstream=True)):
+ yield task
+
+ def get_leaves(self):
+ """
+ Returns a generator of tasks that are leaf tasks, i.e. those with no downstream
+ dependencies within the TaskGroup
+ """
+ for task in self:
+ if not any(child.is_in_task_group(self.group_ids)
+ for child in task.get_direct_relatives(upstream=False)):
+ yield task
+
+ def __rshift__(self, other):
+ """
+ Implements Self >> Other == self.set_downstream(other)
+ """
+ self.set_downstream(other)
+ return other
+
+ def __lshift__(self, other):
+ """
+ Implements Self << Other == self.set_upstream(other)
+ """
+ self.set_upstream(other)
+ return other
+
+ def __rrshift__(self, other):
+ """
+ Called for Operator >> [Operator] because list don't have
+ __rshift__ operators.
+ """
+ self.__lshift__(other)
+ return self
+
+ def __rlshift__(self, other):
+ """
+ Called for Operator << [Operator] because list don't have
+ __lshift__ operators.
+ """
+ self.__rshift__(other)
+ return self
+
+ @classmethod
+ def build_task_group(cls, tasks):
+ """
+ Put tasks into TaskGroup.
+ """
+ root = TaskGroup.create_root()
+ for task in tasks:
+ current = root
+ for label in task.task_group_ids:
+ if label not in current.children:
+ child_group = TaskGroup(group_id=label, parent_group=current)
+ else:
+ child_group = current.children[label]
+ current = child_group
+ current.add(task)
+ return root
+
+
+class TaskGroupContext:
+ """
+ TaskGroup context is used to keep the current TaskGroup when TaskGroup is used as ContextManager.
+ """
+
+ _context_managed_task_group: Optional[TaskGroup] = None
+ _previous_context_managed_task_groups: List[TaskGroup] = []
+
+ @classmethod
+ def push_context_managed_task_group(cls, task_group: TaskGroup):
+ """
+ Push a TaskGroup into the list of managed TaskGroups.
+ """
+ if cls._context_managed_task_group:
+ cls._previous_context_managed_task_groups.append(cls._context_managed_task_group)
+ cls._context_managed_task_group = task_group
+
+ @classmethod
+ def pop_context_managed_task_group(cls) -> Optional[TaskGroup]:
+ """
+ Pops the last TaskGroup from the list of manged TaskGroups and update the current TaskGroup.
+ """
+ old_task_group = cls._context_managed_task_group
+ if cls._previous_context_managed_task_groups:
+ cls._context_managed_task_group = cls._previous_context_managed_task_groups.pop()
+ else:
+ cls._context_managed_task_group = None
+ return old_task_group
+
+ @classmethod
+ def get_current_task_group(cls) -> Optional[TaskGroup]:
+ """
+ Get the current TaskGroup.
+ """
+ if not cls._context_managed_task_group:
+ return TaskGroup.create_root()
Review comment:
should a user expect `_context_managed_task_group` to always point to current task group? if so, should we set `_context_managed_task_group` to this newly created task group before returning?
##########
File path: airflow/utils/task_group.py
##########
@@ -0,0 +1,233 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements. See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership. The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# 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
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""
+TaskGroup
+"""
+
+from typing import List, Optional
+
+
+class TaskGroup:
+ """
+ A collection of tasks. Tasks within the TaskGroup have their task_id prefixed with the
+ group_id of the TaskGroup. When set_downstream() or set_upstream() are called on the
+ TaskGroup, it is applied across all tasks within the group if necessary.
+ """
+ def __init__(self, group_id, parent_group=None):
+ if group_id is None:
+ # This creates a root TaskGroup.
+ self.parent_group = None
+ else:
+ if not isinstance(group_id, str):
+ raise ValueError("group_id must be str")
+ if not group_id:
+ raise ValueError("group_id must not be empty")
+ self.parent_group = parent_group or TaskGroupContext.get_current_task_group()
+
+ self._group_id = group_id
+ if self.parent_group:
+ self.parent_group.add(self)
+ self.children = {}
+
+ @classmethod
+ def create_root(cls):
+ """
+ Create a root TaskGroup with no group_id or parent.
+ """
+ return cls(group_id=None)
+
+ @property
+ def is_root(self):
+ """
+ Returns True if this TaskGroup is the root TaskGroup. Otherwise False
+ """
+ return not self.parent_group
+
+ def __iter__(self):
+ for child in self.children.values():
+ if isinstance(child, TaskGroup):
+ for inner_task in child:
+ yield inner_task
+ else:
+ yield child
+
+ def add(self, task):
+ """
+ Add a task to this TaskGroup.
+ """
+ if task.label in self.children:
+ raise ValueError(f"Duplicate label {task.label} in {self.group_id}")
+ self.children[task.label] = task
+
+ @property
+ def label(self):
+ """
+ group_id excluding parent's group_id.
+ """
+ return self._group_id
+
+ @property
+ def group_id(self):
+ """
+ group_id is prefixed with parent group_id if applicable.
+ """
+ if not self.group_ids:
+ return None
+
+ return ".".join(self.group_ids)
+
+ @property
+ def group_ids(self):
+ """
+ Returns all the group_id of nested TaskGroups as a list, starting from the top.
+ """
+ return list(self._group_ids())[1:]
+
+ def _group_ids(self):
+ if self.parent_group:
+ for group_id in self.parent_group._group_ids(): # pylint: disable=protected-access
+ yield group_id
+
+ yield self._group_id
+
+ def set_downstream(self, task_or_task_list) -> None:
Review comment:
nit, could you add type hints to methods in this class?
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