> 30 nov 2014 kl. 14:53 skrev Soumya Simanta <soumya.sima...@gmail.com>:
>
> As far as I know the following only two options:
>
> 1. Use a requestId (or context object as in Spray) that you pass along with
> your messages to your actors in the chain. The advantage is that you are not
> setting a timeout here. But you have to deal with co-relating messages
> yourself.
> 2. Use the ask pattern where you need to set a timeout but Akka will take
> care of getting the matching the request with the response.
>
> I was wondering if there is any other way of doing this ?
If you consider that the real message is Envelope(payload, sender), these two
options collapse into one: the only way to make sense of the response is to
include identifying information in the request, which can either be placed in
the payload or the sender fields. Using “ask” does the latter by creating a
unique one-time recipient.
You can think of the difference also as
the meta-information travels with the message (and needs to be understood by
the recipient)
the meta-information stays with the sender (in the form of the “ask”-ActorRef
and possible Future transformation closures)
The second case is the only possibility if the recipient’s protocol does not
allow disambiguation:
case Whatever(..., x) =>
otherActor ? Request(...) collect {
case r: Response => ResponseWithContext(r, x)
} pipeTo self
case ResponseWithContext(r, x) =>
// continue the process
The value `x` above is the identifying piece that allows the actor to keep
different requests separate, and if the `otherActor` cannot pass back this
information in its `Response` then we can remember it in the `collect` closure
and piece things together afterwards.
This should motivate why you should always include client-chosen identifiers in
the Actor protocols you design, because that makes this kind of dance
unnecessary (i.e. `Request` should allow passing along `x`—usually called a
correlation ID—and Response should just include that value as well).
Regards,
Roland
>
> Thanks
> -Soumya
>
>
> On Sunday, November 30, 2014 5:39:47 AM UTC-5, Balázs Kossovics wrote:
> Hi Karthik,
>
> Did you check out the ask pattern
> (http://doc.akka.io/docs/akka/snapshot/scala/actors.html#Ask__Send-And-Receive-Future
>
> <http://doc.akka.io/docs/akka/snapshot/scala/actors.html#Ask__Send-And-Receive-Future>)?
> It may be the thing you need.
>
>
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