tracing event's target attribute in SpanData?

[BatmanAoD]

Rust's tracing crate provides a function-instrumentation macro for generating spans. The name of the span is the name of the function, but in general it is not the fully-qualified name of the function, so many different functions may generate spans with the same name.

As far as I can tell, when tracing spans are converted to OTEL spans, the "target" is lost, or at least, not accessible via the SDK (or in Honeycomb, my current OTEL trace collector). In particular, it doesn't seem to be part of SpanData, and I don't see it in the map of span attributes.

It would be helpful to preserve the target since that's the easiest way to uniquely identify the source and meaning of a span when there are multiple functions or methods in different modules or traits that share the same name. Events do have a target, so I'm not sure why spans do not.

Is there a way to get the target string after the conversion from a tracing span to an OTEL span?

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One potentially convenient way to use the target (though it would be a breaking change) would be to use {target}::{name} as the OTEL span name, rather than using the tracing span name directly.

[cijothomas]

This is a good question/feature-request for the "tracing -> otel span bridge" (tracing-opentelemetry crate). It is not maintained in this repo. Can you raise this in https://github.com/tokio-rs/tracing-opentelemetry/issues?

target is something that maps well to OTel's InstrumentationScope name - that'd be the best way to model target, instead of changing SpanName itself or as Attributes.

[BatmanAoD]

Thanks, I've gone ahead and done that: tokio-rs/tracing-opentelemetry#219 (comment)

[BatmanAoD]

Regarding the last paragraph, there are some existing tracing feature requests for changing the name produced by tracing:instrument:

• tracing::instrument 'namespacing' tokio-rs/tracing#1123
• Use qualified function names for span names generated by #[instrumented]. tokio-rs/tracing#2116
• Add trait/type name to the span name on trait methods that use instrument tokio-rs/tracing#1939