Stage failure on an actor

[valentina-2000]

Hi, I have a question. If I've got a graph stage running inside an actor and the stage fails, is the actor aware abotut the failed stage?
How can I catch this exception inside the actor?

[richardjharding]

@valentina-2000 I responded to this on the discord before I realised you raised it here - I have used the PipeTo extension on the task to have any messages including extensions sent to the "Self" actor ref and handle them there - I log them and attempt to restart the flow

I think you can also do this with stream Attributes but I've not found a good example yet

[Aaronontheweb]

@richardjharding 's answer is good, but another tool you can use is the WatchTermination stream stage. This stage exposes a Task that will complete when the stream stage terminates in both failure and successful cases.

In a failure case that Task will fail with an Exception - you can pipe that failure back to the parent actor.

akka.net/src/core/Akka.Streams.Tests/Dsl/FlowWatchTerminationSpec.cs

Lines 86 to 97 in 8e2e11d

	await this.AssertAllStagesStoppedAsync(() => {
	var t =
	Source.Empty<int>()
	.WatchTermination(Keep.Right)
	.ToMaterialized(this.SinkProbe<int>(), Keep.Both)
	.Run(Materializer);
	var future = t.Item1;
	var p = t.Item2;
	p.Request(1);
	future.Wait(TimeSpan.FromSeconds(3)).Should().BeTrue();
	return Task.CompletedTask;
	}, Materializer);

var future = t.Item1; <- this is the termination Task