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Posted to commits@airflow.apache.org by GitBox <gi...@apache.org> on 2020/12/01 17:06:22 UTC
[GitHub] [airflow] VeenaArv opened a new pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
VeenaArv opened a new pull request #12741:
URL: https://github.com/apache/airflow/pull/12741
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closes: 12298
link: https://github.com/apache/airflow/issues/12298
Adds a section under TaskGroup to compare it to SubDAGs.
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[GitHub] [airflow] jhtimmins commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
jhtimmins commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-833240069
Hi @VeenaArv, are you still interested in getting this merged?
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[GitHub] [airflow] boring-cyborg[bot] commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
boring-cyborg[bot] commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-736688127
Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst)
Here are some useful points:
- Pay attention to the quality of your code (flake8, pylint and type annotations). Our [pre-commits]( https://github.com/apache/airflow/blob/master/STATIC_CODE_CHECKS.rst#prerequisites-for-pre-commit-hooks) will help you with that.
- In case of a new feature add useful documentation (in docstrings or in `docs/` directory). Adding a new operator? Check this short [guide](https://github.com/apache/airflow/blob/master/docs/howto/custom-operator.rst) Consider adding an example DAG that shows how users should use it.
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[GitHub] [airflow] github-actions[bot] commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-793199285
This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.
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[GitHub] [airflow] ryw commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
ryw commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-737280674
I'd recommend stronger language against subdags. I know @mistercrunch has an opinion on this that we could add.
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[GitHub] [airflow] potiuk commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
potiuk commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-739792222
Should we complete the review before 2.0.0rc1 tomorrow? @ryw @VeenaArv @turbaszek -> this one needs some love I think.
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[GitHub] [airflow] turbaszek commented on a change in pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
turbaszek commented on a change in pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#discussion_r533589030
##########
File path: docs/apache-airflow/concepts.rst
##########
@@ -1022,6 +1023,28 @@ This animated gif shows the UI interactions. TaskGroups are expanded or collapse
.. image:: img/task_group.gif
+While TaskGroups and SubDAGs are both used to create repeating patterns, depending on your use case, one may be better
+than the other. The SubDagOperator launches a DAG as a separate entity from the original graph. This design pattern
+offers flexibility to create SubDAGs with different schedulers and executors at the cost of greater complexity and
+maintenance burden. TaskGroups creates a UI grouping concept on the same original DAG which simplifies logic and
+maintenance for less flexibility.
Review comment:
How users can schedule SubDAGs using different scheduler or executor?
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[GitHub] [airflow] zuk commented on a change in pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
zuk commented on a change in pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#discussion_r562715639
##########
File path: docs/apache-airflow/concepts.rst
##########
@@ -1022,6 +1023,28 @@ This animated gif shows the UI interactions. TaskGroups are expanded or collapse
.. image:: img/task_group.gif
+While TaskGroups and SubDAGs are both used to create repeating patterns, depending on your use case, one may be better
+than the other. The SubDagOperator launches a DAG as a separate entity from the original graph. This design pattern
+offers flexibility to create SubDAGs with different schedulers and executors at the cost of greater complexity and
+maintenance burden. TaskGroups creates a UI grouping concept on the same original DAG which simplifies logic and
+maintenance for less flexibility.
+
+Here is a table that summarizes their differences:
++----------------------+----------------------+
+| Task Group | SubDAG |
++======================+======================+
+| Repeating patterns | Repeating patterns |
+| live on the same DAG | run as separate DAGs|
++----------------------+----------------------+
+| Follows schedule of | Creates a new |
+| DAG | schedule |
++----------------------+----------------------+
+| Has same executor as | Can specify an |
+| DAG | executor |
++----------------------+----------------------+
+| Honors all pool | Does not honor pool |
+| configurations | configurations |
++----------------------+----------------------+
Review comment:
This is very helpful, but one thing still not clear to me from these docs: Since SubDAGs can have different schedules, how does a SubDAG's execution trigger or block executions of tasks further down in the parent DAG?
For example, if a SubDAG is scheduled to execute every 1 hour, and the parent DAG is scheduled every 20 minutes, will the SubDAG be executed every 20 minutes?
Or if the schedules were reversed (SubDAG every 20 minutes and parent DAG every hour), how do the SubDAG's multiple executions in that hour factor into the parent DAG's eventual execution?
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[GitHub] [airflow] github-actions[bot] commented on pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
github-actions[bot] commented on pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#issuecomment-736741625
[The Workflow run](https://github.com/apache/airflow/actions/runs/394381602) is cancelling this PR. It has some failed jobs matching ^Pylint$,^Static checks,^Build docs$,^Spell check docs$,^Backport packages$,^Provider packages,^Checks: Helm tests$,^Test OpenAPI*.
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[GitHub] [airflow] github-actions[bot] closed pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
github-actions[bot] closed pull request #12741:
URL: https://github.com/apache/airflow/pull/12741
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[GitHub] [airflow] dinigo commented on a change in pull request #12741: Adds Docs to compare SubDAGs and TaskGroups
Posted by GitBox <gi...@apache.org>.
dinigo commented on a change in pull request #12741:
URL: https://github.com/apache/airflow/pull/12741#discussion_r629970942
##########
File path: docs/apache-airflow/concepts.rst
##########
@@ -1022,6 +1023,28 @@ This animated gif shows the UI interactions. TaskGroups are expanded or collapse
.. image:: img/task_group.gif
+While TaskGroups and SubDAGs are both used to create repeating patterns, depending on your use case, one may be better
+than the other. The SubDagOperator launches a DAG as a separate entity from the original graph. This design pattern
+offers flexibility to create SubDAGs with different schedulers and executors at the cost of greater complexity and
+maintenance burden. TaskGroups creates a UI grouping concept on the same original DAG which simplifies logic and
+maintenance for less flexibility.
+
+Here is a table that summarizes their differences:
++----------------------+----------------------+
+| Task Group | SubDAG |
++======================+======================+
+| Repeating patterns | Repeating patterns |
+| live on the same DAG | run as separate DAGs|
++----------------------+----------------------+
+| Follows schedule of | Creates a new |
+| DAG | schedule |
++----------------------+----------------------+
+| Has same executor as | Can specify an |
+| DAG | executor |
++----------------------+----------------------+
+| Honors all pool | Does not honor pool |
+| configurations | configurations |
++----------------------+----------------------+
Review comment:
There are two parts here:
* Parent DAG "SubDAG task" β This is the link between the two: the parent and the SubDAG. It is runs a "Sensor" underneath. I think you can even specify the poking interval.
* SubDAG "DAG" β Can be added to the `global` scope to make it available in the main screen, have different schedule intervals... just like a regular DAG. Only limitation is the name (AFAIK).
SubDAG could easily be renamed as `ExternalDagSensor`
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