def _connect_ping_listener(connection, branch):
    if branch:
        return

    # turn off "close with result".  This can also be accomplished
    # by branching the connection, however just setting the flag is
    # more performant and also doesn't get involved with some
    # connection-invalidation awkardness that occurs (see
    # https://bitbucket.org/zzzeek/sqlalchemy/issue/3215/)
    save_should_close_with_result = connection.should_close_with_result
    connection.should_close_with_result = False
    try:
        # run a SELECT 1.   use a core select() so that
        # any details like that needed by Oracle, DB2 etc. are handled.
        connection.scalar(select([1]))
    except exception.DBConnectionError:
        # catch DBConnectionError, which is raised by the filter
        # system.
        # disconnect detected.  The connection is now
        # "invalid", but the pool should be ready to return
        # new connections assuming they are good now.
        # run the select again to re-validate the Connection.
        connection.scalar(select([1]))
    finally:
        connection.should_close_with_result = save_should_close_with_result
Ping the server at connection startup.
dataset/ETHPy150Open openstack/oslo.db/oslo_db/sqlalchemy/engines.py/_connect_ping_listener