Async request/respone in Proto.Actor? - protractor

Question

I’m new to proto.actor/actor programming and I’m wondering is this possible to achieve this behavior:
Actor A is asking actor B via async command – he should await for response to achieve request/response model but using tasks.
Actor B is using HTTP request so it would be some async IO operation so I don’t want it to be blocked for other actors in this time, so when 10 actors will ask him in the same time each request will be queued but while first request is waiting for process second should get a chance to proceed. Once firs request will be finished it should have priority in queue and get response to actor A.
How to get this flow?
For example I have 3 clients that ask service for some data, service call is taking 5 seconds and most of this time service is spending in IO. With current implementation we have 15 second in total for all requests but I would like it to take ~5-6 second
public static class ProtoTest
{
public static PID Service;
public static async Task Start()
{
var context = new RootContext();
var props = Props.FromProducer(() => new ClientActor());
var serviceProps = Props.FromProducer(() => new ServiceActor());
Service = context.Spawn(serviceProps);
var jobs = new List<Task>();
for (int i = 0; i < 3; i++)
{
string actorName = $"Actor_{i}";
jobs.Add(Task.Run(() =>
{
var client = context.SpawnNamed(props, actorName);
context.Send(client, new Command());
}));
}
Console.ReadLine();
}
}
public class ClientActor : IActor
{
public virtual async Task ReceiveAsync(IContext context)
{
if (context.Message is Command)
{
Console.WriteLine($"{DateTime.Now.ToLongTimeString()} START processing by {context.Self.Id}");
var result = await context.RequestAsync<string>(ProtoTest.Service, new Query());
Console.WriteLine($"{DateTime.Now.ToLongTimeString()} End processing by {context.Self.Id}");
}
return;
}
}
public class ServiceActor : IActor
{
public async virtual Task ReceiveAsync(IContext context)
{
if (context.Message is Query)
{
// this operation is taking long time so actor could handle others in this time
await Task.Delay(5000);
context.Respond("result");
}
return;
}
}

Answer 1

One of the core principles of an actor is that it does not perform multiple operations in parallel. If I understand your problem correctly, what you can do instead is to create a new actor for each operation that you want to run in parallel (actors are cheap so creating many is not an issue). So if actor A needs to send N commands to be processed asynchronously and receive each result as they come in, it could spawn N actors, B1,B2...Bn (one for each command) and send a Request to each of them. The B actors await the result and then Respond back to the A actor. Each response would then be sent as a message to actor A's mailbox and be processed sequentially in the order they complete.