Futures, Promises and Actors

[Alan Burlison]

I was browsing through "Effective Akka" and I noticed the following
somewhat cryptic warning:

----------
Warning
Futures should never be passed between actors because you cannot
serialize a thread.
----------

along with a bit above it about why Actor-to-Actor completion can't be
signalled using a Promise/Future:

"You cannot return a future value from a promise - they cannot be sent
to an actor, which may or may not be remote."

Why? Is this an implementation detail perhaps?

Thanks,

--
Alan Burlison
--

[Konrad “ktoso” Malawski]

Hi Alan,

the reason is basically that a Future represents some computation that is “running” (same as a Thread),

so serializing it does not make much sense. (Yes, there’s trickery and magic we could do, but we avoid such magic tricks).

Rather, use the `future pipeTo someActor` pattern to deal with futures and actors, as documened here: 

https://doc.akka.io/docs/akka/2.5/futures.html#use-with-actors

Happy hakking

-- 

Cheers,

Konrad 'ktoso' Malawski

Akka @ Lightbend

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[Alan Burlison]

On 21/02/18 04:15, Konrad “ktoso” Malawski wrote:

> Hi Alan, the reason is basically that a Future represents some
> computation that is “running” (same as a Thread), so serializing it
> does not make much sense. (Yes, there’s trickery and magic we could
> do, but we avoid such magic tricks).
>
> Rather, use the `future pipeTo someActor` pattern to deal with
> futures and actors, as documened here:
> https://doc.akka.io/docs/akka/2.5/futures.html#use-with-actors

OK, makes sense - thanks for the explanation :-)

--
Alan Burlison
--