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Iuliia Volkova commented on AIRFLOW-1419: ----------------------------------------- [~conradlee], without dummy task, you don't have a branch, you just have the task confluence_op what depend on branch_op, it means confluence_op is a branch by itself, it not depend on some branch, it's branch. We don't have in Airflow edges what you can say - o, this edge is Branch without a task. In your case on your picture, confluence_op - is a branch of branch operator, what never be returned by branch operator and it also depends on the result of another branch. > Trigger Rule not respected downstream of BranchPythonOperator > ------------------------------------------------------------- > > Key: AIRFLOW-1419 > URL: https://issues.apache.org/jira/browse/AIRFLOW-1419 > Project: Apache Airflow > Issue Type: Bug > Affects Versions: 1.8.2 > Reporter: Conrad Lee > Priority: Major > > Lets consider the following DAG: > {noformat} > ____________________ > / \ > branch_op confluence_op > \______work_op________/ > {noformat} > This is implemented in the following code: > {code:java} > import airflow > from airflow.operators.python_operator import BranchPythonOperator > from airflow.operators.dummy_operator import DummyOperator > from airflow.utils.trigger_rule import TriggerRule > from airflow.models import DAG > args = { > 'owner': 'airflow', > 'start_date': airflow.utils.dates.days_ago(2) > } > dag = DAG( > dag_id='branch_skip_problem', > default_args=args, > schedule_interval="@daily") > branch_op = BranchPythonOperator( > task_id='branch_op', > python_callable=lambda: 'work_op', > dag=dag) > work_op = DummyOperator(task_id='work_op', dag=dag) > confluence_op = DummyOperator(task_id='confluence_op', dag=dag, > trigger_rule=TriggerRule.ALL_DONE) > branch_op.set_downstream(confluence_op) > branch_op.set_downstream(work_op) > work_op.set_downstream(confluence_op) > {code} > Note that branch_op is a BranchPythonOperator, work_op and confluence_op are > DummyOperators, and that confluence_op has its trigger_rule set to ALL_DONE. > In dag runs where brancher_op chooses to activate work_op as its child, > confluence_op never runs. This doesn't seem right, because confluence_op has > two parents and a trigger_rule set that it'll run as soon as all of its > parents are done (whether or not they are skipped). > I know this example seems contrived and that in practice there are better > ways of conditionally executing work_op. However, this is the minimal code to > illustrate the problem. You can imagine that this problem might actually > creep up in practice where originally there was a good reason to use the > BranchPythonOperator, and then time passes and someone modifies one of the > branches so that it doesn't really contain any children anymore, thus > resembling the example. -- This message was sent by Atlassian JIRA (v7.6.3#76005)