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

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

Alejandro Fernandez created AIRFLOW-2442:
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             Summary: 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
             Fix For: Airflow 2.0


*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}settings.configure_orm(disable_connection_pool=True)\{code} correctly
to use a NullPool, but then parses any custom configs and again calls \{code}settings.configure_orm()\{code}, thereby overriding the desired behavior with a QueuePool.
The QueuePool uses the default configs for SQL_ALCHEMY_POOL_SIZE (5 connections) and SQL_ALCHEMY_POOL_RECYCLE (1 hour). 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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