[jira] [Commented] (AIRFLOW-3060) DAG context manager fails to exit properly in certain circumstances

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AIRFLOW-3060?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16614107#comment-16614107 ] 

ASF GitHub Bot commented on AIRFLOW-3060:
-----------------------------------------

newtonle opened a new pull request #3900: [AIRFLOW-3060] DAG context manager fails to exit properly in certain circumstances
URL: https://github.com/apache/incubator-airflow/pull/3900
 
 
   Make sure you have checked _all_ steps below.
   
   ### Jira
   
   - [x] My PR addresses the following [Airflow Jira](https://issues.apache.org/jira/browse/AIRFLOW/) issues and references them in the PR title. For example, "\[AIRFLOW-XXX\] My Airflow PR"
     - https://issues.apache.org/jira/browse/AIRFLOW-3060
     - In case you are fixing a typo in the documentation you can prepend your commit with \[AIRFLOW-XXX\], code changes always need a Jira issue.
   
   ### Description
   
   - [x] Here are some details about my PR, including screenshots of any UI changes:
   
   Added an attribute `_context_manager_set` to `DAG` to keep track if the context has already been entered. the `__enter__` and `__exit__` methods have been modified to utilize this attribute and optionally set `_CONTEXT_MANAGER_DAG`. 
   
   ### Tests
   
   - [x] My PR adds the following unit tests __OR__ does not need testing for this extremely good reason:
   additional tests in models.py:test_dag_as_context_manager
   
   ### Commits
   
   - [x] My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "[How to write a good git commit message](http://chris.beams.io/posts/git-commit/)":
     1. Subject is separated from body by a blank line
     1. Subject is limited to 50 characters (not including Jira issue reference)
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     1. Body explains "what" and "why", not "how"
   
   ### Documentation
   
   - [x] In case of new functionality, my PR adds documentation that describes how to use it.
     - When adding new operators/hooks/sensors, the autoclass documentation generation needs to be added.
   
   ### Code Quality
   
   - [x] Passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
   
   @aoen please have a look!

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> DAG context manager fails to exit properly in certain circumstances
> -------------------------------------------------------------------
>
>                 Key: AIRFLOW-3060
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-3060
>             Project: Apache Airflow
>          Issue Type: Bug
>          Components: DAG
>            Reporter: Newton Le
>            Assignee: Newton Le
>            Priority: Major
>
> In certain circumstances, such as in more complex DAGs where users utilize helper functions to add tasks, it may be possible to get into a condition where effectively there is a nested DAG context using the same DAG. When this happens, exiting both contexts does not reset `_CONTEXT_MANAGER_DAG`.
> This is especially problematic because the problem is seen in a later DAG, and the source of the error is not apparent.



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