flaky test: test_active_relay_inactive

[dignifiedquire]

• https://github.com/n0-computer/iroh/actions/runs/19119312719/job/54636059695
• https://github.com/n0-computer/iroh/actions/runs/19118166431/job/54632383347
• https://github.com/n0-computer/iroh/actions/runs/19065026815/job/54453447001

[Frando]

Still very flaky, marked as such in #3619
Two most recent fails:
https://github.com/n0-computer/iroh/actions/runs/19439155525/job/55617804850
https://github.com/n0-computer/iroh/actions/runs/19438760557/job/55616503320

There was #3537 which tried to fix it, but apparently not enough

[dignifiedquire]

@matheus23 can you take a look at this? I believe you wrote the original test

[matheus23]

Pretty sure @flub is to thank for the test!
I'll take a look though ✌️

[matheus23]

So what I've found is: All the currently failing tests don't really show any bugs in the code.

The test setup is somewhat weird though. I think I remember adding the tokio::time::pause() stuff.
However, while we have the tokio pause active, we also do run side-effectful operations. E.g. before we stop in the ActiveRelayActor::run_connected function, we call client_sink.close().await.
In the underlying test this will actually call both WebSocketStream::poll_close (which will flush any pending messages), and even deeper call TcpStream::close (or something like that I think), which will interact with the kernel.
In that case it's entirely possible that tokio gets into an idle state (waiting for actual I/O), and we just wrap that with a tokio::timeout(Duration::from_millis(1000), ...), which gets triggered immediately due to the tokio::time::pause().

That said, I wasn't able to reproduce this locally.

I think there's two possible avenues for trying to fix this:

1. We avoid I/O entirely by somehow hacking in a test version of the client_sink. I think we already have some kind of test version of Conn in iroh-relay, but it might not be exposed.
2. We avoid tokio::time::pause and use tokio::time::advance only for triggering the idle timeout in the relay actor.