Airflow是一个用Python编写的开源平台,用于管理和计划复杂的工作流。它允许用户定义有向无环图(DAG),其中包括一系列可相互依赖的任务。但是,在某些情况下,您可能需要动态地添加任务以及修改依赖关系。
可以通过Airflow提供的PythonOperator和BranchPythonOperator来实现这一点。PythonOperator允许您定制要在DAG中运行的Python函数,而BranchPythonOperator允许您基于函数的输出路径动态地控制任务的流程。
下面是一个示例代码,演示了如何使用PythonOperator创建动态任务和使用BranchPythonOperator设置下游依赖项。
from airflow.models import DAG
from airflow.operators.python_operator import PythonOperator, BranchPythonOperator
from datetime import datetime
default_args = {
'start_date': datetime(2021, 1, 1)
}
def create_dynamic_task(task_id):
def _create_dynamic_task():
print(f"Creating dynamic task {task_id}")
return _create_dynamic_task
def create_dynamic_tasks(**kwargs):
dag = kwargs['dag']
tasks = ['task_1', 'task_2', 'task_3']
for task in tasks:
op = PythonOperator(
task_id=task,
python_callable=create_dynamic_task(task),
dag=dag
)
op.set_upstream(kwargs['start'])
op.set_downstream(kwargs['end'])
yield op
def check_condition():
return ['branch_1', 'branch_2', 'branch_3']
def create_branch_tasks(**kwargs):
branch = kwargs['ti'].xcom_pull(key=None, task_ids=None)
for task in branch:
op = PythonOperator(
task_id=task,
python_callable=lambda:print(f"Running branch task {task}"),
dag=kwargs['dag']
)
op.set_upstream(kwargs['start'])
op.set_downstream(kwargs['end'])
yield op
with DAG('dynamic_dag', default_args=default_args, schedule_interval=None) as dag:
start = PythonOperator(
task_id='start',
python_callable=lambda:print("Starting dynamic DAG..."),
dag=dag
)
end = PythonOperator(
task_id='end',
python_callable=lambda:print("...ending dynamic DAG."),
dag=dag
)
dynamic_tasks = create_dynamic_tasks(start=start, end=end, dag=dag)
branch_tasks = Branch