Tasks have lost their wakers

[IlliaJoker]

While monitoring tasks using tokio-console, I see the following issue:
task has lost their wakers: /axum-0.8.0-rc.1/src/serve.rs:268:13

[Turbo87]

can you share a project that reproduces the issue? without more details this is a bit hard to debug

[paolobarbolini]

That's probably just because the Future returned by tokio::spawn is dropped https://docs.rs/crate/axum/0.8.0-rc.1/source/src/serve.rs#268

[IlliaJoker]

@paolobarbolini Is this correct behavior for this case?

[paolobarbolini]

@paolobarbolini Is this correct behavior in this case?

It might be, but I'm not sure. One thing I'd try doing, since I see you're using an outdated tokio version (1.39.2), is update everything via cargo update and see if anything changes. I don't have much experience with tokio-console but it might be just a false positive. Going through their issues they had some of those in the past.

[Turbo87]

it looks like tokio-console points to https://github.com/tokio-rs/axum/blob/axum-v0.8.0-rc.1/axum/src/serve.rs#L268-L272, and, if I understand correctly, the only waker in this task is the signal, which is passed into the with_graceful_shutdown() fn. if that passed in signal loses its waker then that seems most likely not something that is controlled by axum, but by the surrounding code. you might want to check what you pass into with_graceful_shutdown() and whether that is dropped early or anything like that. as I mentioned above, without a project that reproduces the issue this is very hard to debug.

[jplatte]

To me this seems pretty likely to be when not using graceful shutdown, where internally we use a graceful shutdown future of std::future::Pending IIRC. This means the wait-for-graceful-shutdown task leaks. We should probably fix that.

[IlliaJoker]

I added graceful shutdown to my project, and it helped eliminate task leaks.
Thank you!

[jplatte]

I think this should also fix it: #3129
Can somebody confirm?