let engine
    ?(database_parameters=default_database_path)
    ?(turn_unix_ssh_failure_into_target_failure=false)
    ?host_timeout_upper_bound
    ?(maximum_successive_attempts=10)
    () = {
  database_parameters;
  turn_unix_ssh_failure_into_target_failure;
  host_timeout_upper_bound;
  maximum_successive_attempts;
}