How to make a Supervisor **never** die?

The point of max_restarts (and max_seconds) option is to break the endless restart cycle, and move recovery to the higher level. Thus, in my opinion, an infinity restart option doesn’t make sense. You could approximate it by e.g. using some insanely large number for both options, but I’d advise against doing it.

There are some alternative approaches which could be considered, but first I’d like to learn more about what do these workers do, and why can they restart so frequently?

It sounds like you need to manage this with some form of backoff. You can’t code to prevent anything bad from ever happening, that’s just not possible. But if you have some idea of what can go wrong (and it sounds like you do), you should handle those expected errors. This might be in the form of try/catches, exponential backoff in trying to connect with gun etc. You would in this case put that logic in the worker, not in the Supervisor, and not rely on crashes to refresh the state in cases of known errors.

If that’s for some reason not possible, set the worker strategy to transient and let a separate process handle the restarts. This is not exactly the reason for, but kind of fits into, the use case for the new Registry.select in 1.9, where you would be able to register your workers and then query the Registry for the status of the workers, restarting as required. You’d then be able to keep track of workers that keep crashing, backoff and notify/alert, but keep the other workers living. This can also be implemented by using Process.monitor. Note that this is making your life difficult for yourself, and you’re introducing a lot more risk for corrupted states.

When it comes to the unknown, there’s no way for you to keep the system working in a functioning condition. For those cases crashing is correct.

Don’t design around promises you can’t keep. This is central to the erlang philosophy. Your server will go bad. The network will go bad. Design to handle these.