William Clark created AIRFLOW-145:
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Summary: trigger_rule='one_success' not allowing tasks downstream
of a BranchPythonOperator to be executed
Key: AIRFLOW-145
URL: https://issues.apache.org/jira/browse/AIRFLOW-145
Project: Apache Airflow
Issue Type: Bug
Components: operators
Affects Versions: Airflow 1.7.0
Environment: Airflow version: 1.7.0rc3
Airflow components: webserver, scheduler, worker, postgres database,
CeleryExecutor
Relevant airflow.cfg settings: nothing special here; mostly defaults
Python Version: 3.4.3
Operating System: Centos 6.7
Python packages: virtualenv with standard airflow install
Reporter: William Clark
Background
We are constructing a workflow to automate standard business processes around
the creation and maintenance of virtual machines. After creation, we verify
several information points on the VM to ensure that it is a viable machine and
that no configuration errors occurred. If it fails verification and is not
running, then it should be deleted. If it fails verification and is running,
then we stop it first, then delete it.
What did you expect to happen?
After researching the BranchPythonOperator, I found that I should be using
trigger_rule='one_success' to allow a task at a join point downstream of the
branch(es) to be triggered, as mentioned in #1078. So, I defined the task as
follows:
delete_vm = PythonOperator(
task_id='delete_vm',
trigger_rule=TriggerRule.ONE_SUCCESS,
python_callable=_delete_vm,
provide_context=True,
dag=dag)
delete_vm.set_upstream({poll_vm_stop, verify_vm})
What happened instead?
Rather than executing correctly, the delete_vm task is marked as skipped and is
not re-evaluated following poll_vm_stop. There is no stack trace available, as
the task simply does not execute.
reference: https://github.com/apache/incubator-airflow/issues/1521
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