[jira] [Created] (AIRFLOW-1559) MySQL warnings about aborted connections, missing engine disposal

["Daniel Huang (JIRA)" <ji...@apache.org>]

Daniel Huang created AIRFLOW-1559:
-------------------------------------

             Summary: MySQL warnings about aborted connections, missing engine disposal
                 Key: AIRFLOW-1559
                 URL: https://issues.apache.org/jira/browse/AIRFLOW-1559
             Project: Apache Airflow
          Issue Type: Bug
          Components: db
            Reporter: Daniel Huang
            Priority: Minor


We're seeing a flood of warnings about aborted connections in our MySQL logs. 

{code}
Aborted connection 56720 to db: 'airflow' user: 'foo' host: 'x.x.x.x' (Got an error reading communication packets)
{code}

It appears this is because we're not performing [engine disposal|http://docs.sqlalchemy.org/en/latest/core/connections.html#engine-disposal]. The most common source of this warning is from the scheduler, when it kicks off new processes to process the DAG files. Calling dispose in https://github.com/apache/incubator-airflow/blob/master/airflow/jobs.py#L403 greatly reduced these messages. However, the worker is still causing some of these, I assume from when we spin up processes to run tasks. We do call dispose in https://github.com/apache/incubator-airflow/blob/master/airflow/models.py#L1394-L1396, but I think it's a bit early. Not sure if there's a place we can put this cleanup to ensure it's done everywhere.

Quick script to reproduce this warning message:

{code}
from airflow import settings
from airflow.models import Connection

session = settings.Session()
session.query(Connection).count()
session.close()
# not calling settings.engine.dispose()
{code}

Reproduced with Airflow 1.8.1, MySQL 5.7, and SQLAlchemy 1.1.13. 



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