| # |
| # 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. |
| """ |
| Example DAG demonstrating the usage of ``@task.branch`` TaskFlow API decorator with depends_on_past=True, |
| where tasks may be run or skipped on alternating runs. |
| """ |
| from __future__ import annotations |
| |
| import pendulum |
| |
| from airflow import DAG |
| from airflow.decorators import task |
| from airflow.operators.empty import EmptyOperator |
| |
| |
| @task.branch() |
| def should_run(**kwargs) -> str: |
| """ |
| Determine which empty_task should be run based on if the execution date minute is even or odd. |
| |
| :param dict kwargs: Context |
| :return: Id of the task to run |
| """ |
| print( |
| f"------------- exec dttm = {kwargs['execution_date']} and minute = {kwargs['execution_date'].minute}" |
| ) |
| if kwargs["execution_date"].minute % 2 == 0: |
| return "empty_task_1" |
| else: |
| return "empty_task_2" |
| |
| |
| with DAG( |
| dag_id="example_branch_dop_operator_v3", |
| schedule="*/1 * * * *", |
| start_date=pendulum.datetime(2021, 1, 1, tz="UTC"), |
| catchup=False, |
| default_args={"depends_on_past": True}, |
| tags=["example"], |
| ) as dag: |
| cond = should_run() |
| |
| empty_task_1 = EmptyOperator(task_id="empty_task_1") |
| empty_task_2 = EmptyOperator(task_id="empty_task_2") |
| cond >> [empty_task_1, empty_task_2] |