[GitHub] [airflow] MatrixManAtYrService opened a new issue #19899: Task group entry/exits hide task dependency

[GitBox <gi...@apache.org>]

MatrixManAtYrService opened a new issue #19899:
URL: https://github.com/apache/airflow/issues/19899


   ### Apache Airflow version
   
   2.2.2 (latest released)
   
   ### Operating System
   
   debian buster (docker)
   
   ### Versions of Apache Airflow Providers
   
   n/a
   
   ### Deployment
   
   Astronomer
   
   ### Deployment details
   
   This dag:
   ```python3
   from datetime import datetime, timedelta
   from time import sleep
   ​
   from airflow.decorators import task, task_group
   from airflow.models.dag import DAG
   from airflow.operators.dummy import DummyOperator
   from airflow.utils.task_group import TaskGroup
   from airflow.utils.trigger_rule import TriggerRule
   ​
   two_days = datetime.now() - timedelta(days=2)
   ​
   ​
   def waiter(secs):
       @task(task_id=str(secs))
       def wait():
           sleep(secs)
   ​
       return wait()
   ​
   ​
   @task_group
   def two():
       t1 = waiter(60)
       t2 = waiter(65)
       bookend = DummyOperator(task_id="bookend")
       [t1, t2] >> bookend
       return bookend
   ​
   ​
   with DAG(
       dag_id="downlow_tooslow",
       schedule_interval=None,
       start_date=two_days,
   ) as dag:
   ​
       # based on the dag image, you'd expect this task group finish last,
       # since it has a 100 second task
       with TaskGroup(group_id="group1") as tg1:
           t1 = waiter(5)
           t50 = waiter(100)
   ​
       # but actually, the blue dot at the end of the group means nothing
       # the dummy below runs after just five seconds
       tg2 = two()
   
       [tg1, tg2] >> DummyOperator(task_id="done", trigger_rule=TriggerRule.ONE_SUCCESS)
   ```
   
   Which looks like this after running for 10 seconds (the numbers refer to seconds that the task will sleep).
   
   <img width="427" alt="Screen Shot 2021-11-29 at 1 47 45 PM" src="https://user-images.githubusercontent.com/5834582/144097666-5d774bea-b97d-4cd9-9081-bccf787535f5.png">
   
   
   ### What happened
   
   The "done" task ran after 5 seconds.
   
   ### What you expected to happen
   
   The graph view leads me to believe that the two things that are upstream of "done" are:
    - group1
    - two
   
   Based on that image, I would expect "done" to run after 65 seconds, which is when the "two" task group is complete.
   
   ### How to reproduce
   
   _No response_
   
   ### Anything else
   
   I know that it will make several dags out there uglier, but unless we want to make task-group entry/exit points into tasks (complete with their own trigger rules) I think the fix is to remove the blue dots entirely so that we avoid misleading the user about task dependency.
   
   ### Are you willing to submit PR?
   
   - [ ] Yes I am willing to submit a PR!
   
   ### Code of Conduct
   
   - [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
   


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