Using `TaskMonitor` with `spawn_blocking`?

[AlJohri]

Is it possible to instrument a spawn_blocking task? I am currently getting this error when I try to instrument the closure being passed into spawn blocking:

expected an `FnOnce()` closure, found `tokio_metrics::Instrumented<{closure@amzn-eureka-broker-node/src/search.rs:604:18: 604:25}>

Our application makes heavy use of both tokio::spawn and tokio::spawn_blocking and I would like to see metrics for both parts of the application.

I think some of the metrics still make sense in the spawn_blocking context like total_first_poll_delay.

[arielb1]

spawn_blocking does not work with tasks, therefore it is not going to work with TaskMonitor without a redesign.

[arielb1]

Opened tokio-rs/tokio#7272 for having a metric on the Tokio side. Once that exists, we can expose it.