dbapi_hook causes mysql error 2014 on large input

[mtustin-handy]

This is the exception:

ProgrammingError: (2014, "Commands out of sync; you can't run this command now")                                                   
2015-09-24 14:54:41,780 - root - ERROR - (2014, "Commands out of sync; you can't run this command now")                            
Traceback (most recent call last):                                                                                                 
  File "/home/mtustin/airflowvenv/bin/airflow", line 10, in <module>                                                               
    args.func(args)                                                                                                                
  File "/home/mtustin/airflowvenv/lib/python2.7/site-packages/airflow/bin/cli.py", line 204, in test                               
    ti.run(force=True, ignore_dependencies=True, test_mode=True)                                                                   
  File "/home/mtustin/airflowvenv/lib/python2.7/site-packages/airflow/models.py", line 928, in run                                 
    result = task_copy.execute(context=context)                                                                                    
  File "/home/mtustin/airflowvenv/lib/python2.7/site-packages/airflow/operators/mysql_operator.py", line 33, in execute            
    hook.run(self.sql)                                                                                                             
  File "/home/mtustin/airflowvenv/lib/python2.7/site-packages/airflow/hooks/dbapi_hook.py", line 100, in run                       
    conn.commit()                                                                                                                  
_mysql_exceptions.ProgrammingError: (2014, "Commands out of sync; you can't run this command now")                                 

This is the task which is triggering it:

refresh_db = MySqlOperator(                                                                                                        
    mysql_conn_id='clean_db_export',                                                                                               
    sql='templates/dbschema.sql',                                                                                                  
    task_id='refresh_db',                                                                                                          
    dag=clean_and_export_dag)

templates/dbschema.sql is the result of running mysqldump --no-data.

I am able to successfully perform - in a separate task - a 4 line sql script which drops and recreates the database involved here.

The exception does not occur if I switch the order of these two lines: https://github.com/airbnb/airflow/blob/master/airflow/hooks/dbapi_hook.py#L100-L101 to give:

cur.close()
conn.commit()

I am running airflow and mysql on Redhat with kernel 3.10.0-229.el7.x86_64 #1 SMP.

I expect to have a PR open in the course of the day with that change.