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https://issues.apache.org/jira/browse/AIRFLOW-1614?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16167003#comment-16167003
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Gregory Benison commented on AIRFLOW-1614:
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Some profiling suggests this is largely due to the cost of constructing DAG
objects; in particular the call to "inspect.stack" in the constructor is rather
expensive. It's also a bit unnecessary - we only need the caller's frame, but
inspect.stack gives you the whole stack. I have a pull request with one
possible fix (coming soon) that cuts the parsing time of the above file by more
than half on my platform.
> Improve performance of DAG parsing when there are many subdags
> --------------------------------------------------------------
>
> Key: AIRFLOW-1614
> URL: https://issues.apache.org/jira/browse/AIRFLOW-1614
> Project: Apache Airflow
> Issue Type: Improvement
> Reporter: Gregory Benison
>
> DAGs can be very slow to parse when they contain many (100s or 1000s) of
> subdags. This can be illustrated using the following DAG definition file:
> {code}from datetime import datetime, timedelta
> from airflow.models import DAG
> from airflow.operators.dummy_operator import DummyOperator
> from airflow.operators.subdag_operator import SubDagOperator
> dag = DAG(
> 'subdaggy-2',
> schedule_interval=None,
> start_date=datetime(2017,1,1)
> )
> def make_sub_dag(parent_dag, N):
> dag = DAG(
> '%s.task_%d' % (parent_dag.dag_id, N),
> schedule_interval=parent_dag.schedule_interval,
> start_date=parent_dag.start_date
> )
> DummyOperator(task_id='task1', dag=dag) >> DummyOperator(task_id='task2',
> dag=dag)
> return dag
> downstream_task = DummyOperator(task_id='downstream', dag=dag)
> for N in range(20):
> SubDagOperator(
> dag=dag,
> task_id='task_%d' % N,
> subdag=make_sub_dag(dag, N)
> ) >> downstream_task
> {code}
> When there are more than 50 or so subdags this file becomes slow enough to
> parse that it fails to load in the web UI on a modest platform such as a
> laptop.
> It would be nice to support such DAGs, since there are useful workflows
> involving 100s or 1000s of subdags.
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