If you need to be able to restart because of electricity shutdown, you must have your jobs-to-do in database. In that case a simple solution is to use Oban.
Oban will let you control how much workers you will have in your queue.
Infortunately if the server shutdowns during execution of an Oban job, on restart Oban will believe that the job is still “executing” and will not restart it (except if you use Oban Pro). But if you have a single instance of your application running, that is easy: On start, check if there is any job with the “executing” state in database and set it to “available”. And only then start the Oban queue.
Not sure how Ash could help there though.
