By default, AutoSlave does not remember cross requests, whether a connection is down or not.
To prevent AutoSlave from trying to connect to databases which are known to be down, the "invalidation path" option can be used:
<?php
$databases['default']['default'] = array (
'driver'=> 'autoslave',
'master'=> array('master'),
'slave'=> array('slave'),
'invalidation path'=> 'sites/default/files',
);
?>This will make AutoSlave store the information about not being able to connect, in the file 'sites/default/files/autoslave-invalidation-default.inc'.
AutoSlave's cron job will update the information in the file, when the connection is available again.