Maybe all of this could be replaced with something like

let span_level = connect_span.metadata().map_or(Level::TRACE, |metadata| metadata.level());
tracing::span!(parent: connect_span, span_level, "io_loop")

Also, if you target the lapin-2.x branch instead, I'll cut a release for it, then merge in newer branch and cut 3.x and 4.x releases

A few things:

1. Span level – This can't be dynamic, otherwise yeah that approach would be better! You get this error:

   attempt to use a non-constant value in a constant non-constant value

   Which has serious "how much wood would a woodchuck chuck..." vibes.

   Yeah, this is a kind of annoying limitation of tracing.

2. Relationship with connect span – I decided not to set the connect span as the parent. See the docs from tracing:

   In addition to having zero or one parent, a span may also follow from any number of other spans. This indicates a causal relationship between the span and the spans that it follows from, but a follower is not typically considered part of the duration of the span it follows.

   Which seems to match what we're trying to represent here.

3. Branch target – Grand, I can change that 👍