DefaultSupervisorStratgey.md

The default SupervisorStrategy in Akka

At times it's hard to remember all the details of restarting a faulty actor. So lets take a look at a simple example:

/user/grand-parent/parent/child

Here we have a Child actor with one Parent and one GrandParent actor.

The default SupervisorStrategy will decide to Restart an actor after any NotFatal throwable except for ActorInitializationException, DeathPactException or ActorKilledException in which case the decision will be Stop.

When Parent actor fails ...

What happens...	GrandParent	Parent	Child
`preStart`	Not called	Indirectly called on the new instance from `postRestart`	Not called
`postStop`	Not called	Indirectly called on the old instance from `preRestart`	Called after the actor is stopped
`preRestart`	Not called	Called on the old instance; stops all child actors and calls `postStop` by default	Not called
`postReStart`	Not called	Called on the new instance; calls `preStart` by default	Not called
What happens to mailbox?	N.A.	Still available	Lost
What happens to the current message?	N.A.	Accessible in `preRestart()`	N.A.
What happens to the actor's state?	N.A.	Reset [1]	Lost

Here is an nice example of supervisor stratgey in action

[1] You can use Akka Persistence to restore the internal state