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
tests/www/test_app.py
app = application.cached_app(testing=True)
        app.url_map.add(Rule("/debug", endpoint="debug"))
        def debug_view():
            from flask import request
            
            self.assertEqual(request.remote_addr, '192.168.0.2')