This setting must be either True or False.

This setting specifies whether or not the alias action should continue with a warning or return immediately in the event that the filters in the add or remove section result in an empty index list.

Use with caution. This option is particularly beneficial when trying to alias a new set of time-series indices. For example, you want to add the most recent seven days into a lastweek alias, and remove indices older than seven days from this same alias. If you do not have any indices older than seven days, this will result in an empty index list condition which will prevent the entire alias action from completing successfully. A non-beneficial case would be where a typo results in indices not being removed, and suddenly an alias that should only query one week has three weeks of data.