See [Tarantool server events documentation](https://www.tarantool.io/en/doc/latest/dev_guide/internals/iproto/events/) for more info. See [go-tarantool patch](https://github.com/tarantool/go-tarantool/issues/119) for reference implementation. Watchers are expected to cover cases which are covered by `box.session.push` now. Since the latter is planned to be [removed](https://github.com/tarantool/tarantool-python/issues/305), we need to introduce a proper replacement first. It is a design question how to introduce asynchronous mechanism to a synchronous connector. One way is to use threads like in connection pool health check.