How do Actor Systems function to prevent memory overflow from queues but also prevent threads blocking on writing on the queues?

Question

Actors send messages to one another. If the queues are limited, then what happens on write/send attempts to full queues? Blocking or dropping? If they are not limited, a memory crash is possible. How much is configurable?

Answer 1

Default mailboxes in Akka are not bounded, so will not prevent memory crash. You can however configure actors to use different mailboxes, among those there are both mailboxes that discard (pass to dead letters) messages when the max size is reached and those that block (I would not recommend to use those). You can find all mailbox implementations that comes with Akka in the docs here: https://doc.akka.io/docs/akka/current/typed/mailboxes.html#mailbox-implementations