Akka-remoting with Artery using load balancing/round robbing dns

[johan.kjolhed...@gmail.com]

Case:

I have two services (A and B) that wish to talk to each other using akka-remoting over artery.

Each service executes on it's own machine behind a load balancer mapping a dns name, e.g. $A resolving -> multiple IP addresses.

For A to talk to B, we can for example execute:

// Make request from an A to a B
val b = context.actorSelection(s"akka://$systemName@$B:$port/user/$actorName")
b ! Request()

where $B is the load balanced address that is resolved to a B instance (maybe B1, maybe B2.. etc)

In order for B to receive this message, B would need to have an akka conf with canonical.hostname = $B. Otherwise artery will filter out these messages...

So far, this works. However, now let's say this is bidirectional communication. 

B wants to reply to A's requests, but also, B wants to send its own independent requests to A and expect A to reply back to B.

B would then have something like the following code

// Reply from B back to A
def receive {
  case  Request() => sender() ! Reply()
}

But because A has canonical.hostname set to $A, which is a load balanced address, the reply could end up at A1, A2 or any Ai for that matter.

To work around this, all I can think of is to let each actor resolution actually do a manual dns lookup before calling context.actorSelection.. and write the explicit resolved address of each actor to their own akka conf.

Is this conclusion correct?

I suspect akka.tcp does not have this problem as sender() would just re-use the existing tcp connection, but artery being build on udp, will suffer from the problem above.

Am I missing something? :)

/ Johan

[Viktor Klang]

the host needs to be a stable identifier.

What problem are you trying to solve with the rr dns?

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[johan.kjolhed...@gmail.com]

Ok. Just wanted that confirmed. We already have a workaround for it so I was mostly just curious to see if it was needed :).

/ Johan

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[Endre Varga]

Actor remote messaging is a P2P protocol and as such any kind of name-remapping is harmful. Trying to load balance Akka Remote connections I think is a mistake and makes not much sense. You *can* load balance Akka provided services of course, but you need to expose them as a different protocol (i.e. REST API, custom TCP endpoint, etc.). 

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[Patrik Nordwall]

And for the record, it's just accidental that it works with tcp. We don't guarantee that the same connection is reused.

[Viktor Klang]

Consider that confirmed then. ;)

On Thu, Nov 10, 2016 at 5:12 PM, <johan.kjolhed...@gmail.com> wrote:

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[Johan Kjölhede]

Thanks for clarifying that. We suspected that but weren't sure. We can close this thread ;). Thanks everyone for great input

Skickat från min iPhone

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