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https://issues.apache.org/jira/browse/AIRFLOW-145?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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William Clark updated AIRFLOW-145:
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    Attachment: screenshot-1.png

> 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
>         Attachments: screenshot-1.png
>
>
> 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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