How to add instrument for functions returns `Poll<T>`?

[Xuanwo]

Hi, OpenDAL is currently developing an AwaitTreeLayer to give our users the ability to dump the execution tree at runtime: apache/opendal#2623

The missing part here is that how can we add instrument for functions returns Poll<T>? For example, AsyncRead will have API like the following:

pub trait AsyncRead {
    // Required method
    fn poll_read(
        self: Pin<&mut Self>,
        cx: &mut Context<'_>,
        buf: &mut [u8]
    ) -> Poll<Result<usize, Error>>;

Can we add instrument for every poll operations?

[Xuanwo]

cc @BugenZhao for discussion, thanks!

[BugenZhao]

Great point! In theory, await-tree can be attached to any function that returns Poll. I'll investigate interface design.