tracing_opentelemetry: Version of `OpenTelemetrySpanExt::set_parent` that returns `self`

[joshtriplett]

Feature Request

Crates

tracing_opentelemetry

Motivation

I'd like to create a span, set an OpenTelemetry context as the parent, and then use the span in calls like instrument, without having to create a named let binding for the span.

Proposal

I'd like to propose a function OpenTelemetrySpanExt::with_parent, which acts exactly like set_parent, but accepts self and returns Self.

fn with_parent(self, cx: opentelemetry::Context) -> Self {
    self.set_parent(cx);
    self
}

Such a function would allow code like this:

async { ... }.instrument(info_span!("span details").with_parent(context)).await

Alternatives

The tracing macros could have "native" support for OpenTelemetry contexts as parents:

async { ... }.instrument(info_span!(parent: context, "span details")).await

That seems much harder to implement, though.

[hawkw]

Alternatives

The tracing macros could have "native" support for OpenTelemetry contexts as parents:

I think it's unlikely that we'll implement this approach --- the intention is that tracing and tracing-core should only be a facade layer that's unaware of specific ways of collecting traces or other systems we're integrating with. Therefore, I think adding a new combinator to tracing-opentelemetry's extension trait seems like the right way to do this! 👍

[joshtriplett]

@hawkw I agree entirely, I just mentioned it because it's an alternative. (It'd require some kind of indirection through a trait, I think, so that tracing wouldn't have to know about tracing-opentelemetry.)

I think with_parent seems much simpler.

[jtescher]

@joshtriplett yeah with_parent sounds good to me!