[jira] [Work started] (AIRFLOW-2442) Airflow run command leaves database connections open, which can hit the database limit

["Alejandro Fernandez (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/AIRFLOW-2442?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Work on AIRFLOW-2442 started by Alejandro Fernandez.
----------------------------------------------------
> Airflow run command leaves database connections open, which can hit the database limit
> --------------------------------------------------------------------------------------
>
>                 Key: AIRFLOW-2442
>                 URL: https://issues.apache.org/jira/browse/AIRFLOW-2442
>             Project: Apache Airflow
>          Issue Type: Bug
>          Components: cli
>    Affects Versions: Airflow 1.8, 1.8.0
>            Reporter: Alejandro Fernandez
>            Assignee: Alejandro Fernandez
>            Priority: Major
>             Fix For: Airflow 2.0
>
>         Attachments: AIRFLOW-2442.patch, connection_duration_1_hour.png, db_connections.png, fixed_before_and_after.jpg, monthly_db_connections.png, running_tasks.png
>
>
> *Summary*
> The "airflow run" command creates a connection to the database and leaves it open (until killed by SQLALchemy later). The number of these connections can skyrocket whenever hundreds/thousands of tasks are launched simultaneously, and potentially hit the database connection limit.
> The problem is that in cli.py, the run() method first calls 
> {code:java}
> settings.configure_orm(disable_connection_pool=True){code}
> correctly
>  to use a NullPool, but then parses any custom configs and again calls
> {code:java}
> settings.configure_orm(){code}
> , thereby overriding the desired behavior by instead using a QueuePool.
>  The QueuePool uses the default configs for SQL_ALCHEMY_POOL_SIZE and SQL_ALCHEMY_POOL_RECYCLE. This means that while the task is running and the executor is sending heartbeats, the sleeping connection is idle until it is killed by SQLAlchemy.
> This fixes a bug introduced by [https://github.com/apache/incubator-airflow/pull/1934] in [https://github.com/apache/incubator-airflow/pull/1934/commits/b380013634b02bb4c1b9d1cc587ccd12383820b6#diff-1c2404a3a60f829127232842250ff406R344]  
> which is present in branches 1-8-stable, 1-9-stable, and 1-10-test



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