Back off strategy for persist failures.

Specifically BackOff to prevent resume being used. Resume is not allowed as it will be unknown if the state has been persisted.

This supervision is only around the DurableStateBehavior not any outer setup/withTimers block. If using restart, any actions e.g. scheduling timers, can be done on the PreRestart

If not specified the actor will be stopped on failure.

Allows the DurableStateBehavior to react on signals.

The regular lifecycle signals can be handled as well as DurableStateBehavior specific signals (recovery related). Those are all subtypes of akka.persistence.typed.state.DurableStateSignal

Transform the state to another type before giving to the store. Can be used to transform older state types into the current state type e.g. when migrating from Persistent FSM to Typed DurableStateBehavior.

Define a custom stash capacity per entity. If not defined, the default akka.persistence.typed.stash-capacity will be used.

Narrow the type of this Behavior, which is always a safe operation. This method is necessary to implement the contravariant nature of Behavior (which cannot be expressed directly due to type inference problems).

Transform the incoming messages by placing a funnel in front of the wrapped Behavior: the supplied PartialFunction decides which message to pull in (those that it is defined at) and may transform the incoming message to place them into the wrapped Behavior’s type hierarchy. Signals are not transformed.

Example:

val b: Behavior[Number] =
  Behaviors
    .receive[String] { (ctx, msg) =>
      println(msg)
      Behaviors.same
    }
    .transformMessages[Number] {
      case b: BigDecimal => s"BigDecimal($b)"
      case i: BigInt     => s"BigInteger($i)"
      // all other kinds of Number will be `unhandled`
    }

The ClassTag for Outer ensures that only messages of this class or a subclass thereof will be intercepted. Other message types (e.g. a private protocol) will bypass the interceptor and be continue to the inner behavior untouched.