tokio-console debugger

[BradLugo]

What'd yall think about adding the necessary instrumentation to support the tokio console debugger?
https://github.com/tokio-rs/console

[Molter73]

First time I'm hearing about the tokio console, it looks useful but I'm concerned about including it on all versions of fact by default. Is there any way we could enable it on certain builds and exclude them in others? For instance, add it in debug builds but exclude it in release builds so that shipped images don't have this functionality built in?

[BradLugo]

IIRC, I think we'd need to adjust how we spawn tokio tasks (i.e., using the Builder instead of tokio::spawn(): https://docs.rs/tokio/latest/tokio/runtime/struct.Builder.html) and add the tokio-console subscriber: https://docs.rs/console-subscriber/latest/console_subscriber/

The first change shouldn't be much different from what we do today, and I think the second we could conditional compile in: https://doc.rust-lang.org/reference/conditional-compilation.html

[Molter73]

I'm a bit concerned that adding this requires some unstable tokio features, I'm also a bit worried the instrumentation may have some performance penalty, but we are currently not in a position to test that.

If you have the capacity and want to give it a shot, I will happily review the PR, but I wouldn't call this a high priority at the moment.