SQLAlchemy engine configuration is not passed to FAB based UI. Faced this issue when running Airflow with MySQL metadata store with wait_timeout = 120. Webserver is failing with Internal Server Error due to "[MySQL Server has gone away](https://docs.sqlalchemy.org/en/13/faq/connections.html#mysql-server-has-gone-away)" error. Settings like `sql_alchemy_pool_recycle` and  `sql_alchemy_pool_pre_ping` have no impact on FAB internal communication with MySQL.

**Apache Airflow version**: 1.10.12
airflow/settings.py
"""Configure ORM using SQLAlchemy"""
    log.debug("Setting up DB connection pool (PID %s)", os.getpid())
    global engine
    global Session
    engine_args = {}
    pool_connections = conf.getboolean('core', 'SQL_ALCHEMY_POOL_ENABLED')
    if disable_connection_pool or not pool_connections:
        engine_args['poolclass'] = NullPool
        log.debug("settings.configure_orm(): Using NullPool")
    elif 'sqlite' not in SQL_ALCHEMY_CONN:
        
        
        
        pool_size = conf.getint('core', 'SQL_ALCHEMY_POOL_SIZE', fallback=5)
        
        
        
        
        
        
        
        # ma
        # no 
        # of 
        max_overflow = conf.getint('core', 'SQL_ALCHEMY_MAX_OVERFLOW', fallback=10)
        # Th
        # wh