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From Reed Villanueva <rvillanu...@ucera.org>
Subject airflow graph task branch never runs, complains “Task instance did not exist in the DB”, but can see in graph
Date Wed, 23 Oct 2019 21:16:28 GMT
I have an airflow graph with a conditional branch defined *like*

class BranchFlags(Enum):
    yes = "yes"
    no = "no"...for table in list_of_tables # type list(dict)
    task_1 = BashOperator(
        task_id='task_1_%s' % table["conf1"],
        bash_command='bash script1.sh %s' % table["conf1"],
        dag=dag)

    if table["branch_flag"] == BranchFlags.yes:
        consolidate = BashOperator(
            task_id='task_3_%s' % table["conf2"],
            bash_command='python %s/consolidate_parquet.py %s' % table["conf2"],
            dag=dag)

    task_3 = BashOperator(
        task_id='task_3_%s' % table["conf3"],
        bash_command='bash script3.sh %s' % table["conf3"],
        dag=dag)

    task_1 >> task_3
    if table["branch_flag"] == BranchFlags.yes:
        task_1 >> task_2

and here is the graph in the airflow UI from my actual code: [image: enter
image description here] <https://i.stack.imgur.com/TVwLR.png>

Notice that even though the longer parts of the graph run fine, the lone
branch is not being run for the one sequence that was supposed to branch.
When viewing the logs for the task, I see

*** Task instance did not exist in the DB

This is weird to me, since ostensibly the scheduler DB sees the task since
it does appear in the web UI graph. Not sure what is going on here and
adding other changes to the dag .py file do show up in the graph and are
executed by the scheduler when running the graph. And attempting to view
the tasks Task Instance Details throws error

Task [dagname.task_3_qwerty] doesn't seem to exist at the moment

Running airflow resetdb (as I've seen in other posts) does nothing for the
problem.

Anyone know why this would be happening or have some debugging tips?

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