akkadotnet/akka.net

Port of Akka actors for .NET

Ralf

@Ralf1108

so normal workflow occurs

thx guys for helping out !!! :+1:

Arjen Smits

@Danthar

@maxcherednik passivate is a pattern used to reduce the amount of idle actors in your topology

imagine you have an actor per user in your system

and your routing messages to those user actors

you would have an coordinator as the parent of those user actors

which receives user messages and forwards them to the correct actor

then, depending on a strategy of your own making

for example a timeout

lets say that once a user actor has not seen a message in X amount of time

you want to stop it, so its state is unloaded from memory

the coordinator sends a passivate message to the user actor and starts buffering messages for that actor

actor stops, deathwatch notifies the coordinator

if the coordinator receives messages for that user again

it starts up the actor again

and forwards the message once the actor is up

this kind of pattern is very useful if you have a large pool of stateful actors which only occasionally receive messages.

Arjen Smits

@Danthar

Cluster Sharding uses passivate

Ralf

@Ralf1108

i like this pattern. it allows to manage thousands of actors and only the hotspot actors which are currently in use will be available in memory. similar to a garbage collector

Maxim Cherednik

@maxcherednik

@Danthar I see. Thx. Just never used it.

I am just wondering why don't I have this logic inside the Actor based on timeout - stop self...

then once new message arrives - the parent will just create it again and send the message to it

why do I need to use some kind of buffering or what so ever

Arjen Smits

@Danthar

because actor shutdown is async

the Terminate message is just that. A message

Maxim Cherednik

@maxcherednik

right

Arjen Smits

@Danthar

so you want to buffer to account for race conditions

Maxim Cherednik

@maxcherednik

nowadays, I am trying to offload all the logic like this to the client :) Shutdown - async? ok that will skip the next message, client will retry on timeout :)

Arjen Smits

@Danthar

Thats a choice. Depending on your architecture it might be enough. Although when communicating across the network, if you want reliable delivery, you always end up with that kind of stuff

but the upside is. It can be abstracted away pretty easily

Maxim Cherednik

@maxcherednik

I see

Arjen Smits

@Danthar

"with that kind of stuff" i mean the thing you mentioned. Namely implement retries client side

Maxim Cherednik

@maxcherednik

btw do you always do this?

Arjen Smits

@Danthar

nope

Dont always need guarenteed delivery

And it depends on what your doing

Maxim Cherednik

@maxcherednik

it's kind of a boiler plate code... which you need to implement on every request response

of course if it's a UI call.... I will ask UI guys to timeout and push user to request it again

Jose Carlos Marquez

@oeaoaueaa

hi, whats the approach for a cluster of servers with a "flaky" network connection where some of the nodes are marked as Unreachable? should those nodes restart themselves? if so, how do they know?

Francis Paulin

@paulinfrancis

I've got two console apps that both connect successfully to lighthouse to join a cluster. I would like to publish messages from actors in one console app to actors in the other.

In the "from" console app

var mediator = DistributedPubSub.Get(_actorSystem).Mediator;
mediator.Tell(new ClusterClient.Publish("topic-foo", "my message"));

In an actor in the "to" console app

public RaspberryPiActor()
{
    var mediator = DistributedPubSub.Get(Context.System).Mediator;
    mediator.Tell(new Subscribe("topic-foo", Self));
    Receive<SubscribeAck>(_ => Become(Subscribed));
}

private void Subscribed()
{
    Receive<string>(m =>
    {
        Console.WriteLine(m);
    });
}

Am I doing something that is evidently wrong?

Francis Paulin

@paulinfrancis

All the messages go straight to dead letters.

Jose Carlos Marquez

@oeaoaueaa

what type is the result of: new ClusterClient.Publish("topic-foo", "my message")?

from what I understand, that is the message that is being sent

Francis Paulin

@paulinfrancis

Jose Carlos Marquez

@oeaoaueaa

I think you might be receiving a message of type "Publish", try Receive<Publish>(p => ....) instead

Francis Paulin

@paulinfrancis

No luck I'm afraid, but thanks for the suggestions!

Tried ReceiveAny too, just to be on the safe side

but it never hits the method

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