[jira] [Commented] (AIRFLOW-2128) 'Tall' DAGs scale worse than 'wide' DAGs

["Chris Bandy (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AIRFLOW-2128?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16429355#comment-16429355 ] 

Chris Bandy commented on AIRFLOW-2128:
--------------------------------------

[~szmate1618] what is your {{scheduler.min_file_process_interval}} (or {{AIRFLOW__SCHEDULER__MIN_FILE_PROCESS_INTERVAL}} environment) set to?

> 'Tall' DAGs scale worse than 'wide' DAGs
> ----------------------------------------
>
>                 Key: AIRFLOW-2128
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-2128
>             Project: Apache Airflow
>          Issue Type: Bug
>          Components: DAG, DagRun, scheduler
>    Affects Versions: 1.9.0
>            Reporter: Máté Szabó
>            Priority: Major
>              Labels: performance, usability
>         Attachments: tall_dag.py, wide_dag.py
>
>
> Tall DAG = a DAG with long chains of dependencies, e.g.: 0 -> 1 -> 2 -> ... -> 998 -> 999
>  Wide DAG = a DAG with many short, parallel dependencies e.g. 0 -> 1; 0 -> 2; ... 0 -> 999
> Take a super simple case where both graphs are of 1000 tasks, and all the tasks are just "sleep 0.03" bash commands (see the attached files).
>  With the default SequentialExecutor (without paralellism), I would expect my 2 example DAGs to take (approximately) the same time to run, but apparently this is not the case.
> For the wide DAG it was about 80 successfully executed tasks in 10 minutes, for the tall one it was 0.
> This anomaly also seem to affect the web UI. Opening up the graph view or the tree view for the wide DAG takes about 6 seconds on my machine, but for the tall one it takes significantly longer, in fact currently it does not load at all.



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