Span name should match other implementations

[Andersclark]

opentelemetry-js/experimental/packages/opentelemetry-instrumentation-fetch/src/fetch.ts

Line 221 in 492ed35

const spanName = `HTTP ${method}`;

Problem

In this implementation, a span is given the name of HTTP ${METHOD}, whereas when looking at spans from other sources, such as Dotnet, name has the format of ${METHOD} ${PATH} making it possible to distinguish requests from each other in an overview of traces.

In the image: Yellow traces are sourced from a Dotnet backend. Cyan traces comes from FetchInstrumentation:

Suggested solution

A simple solution with breaking change: Decorate Span name with Request-URL:s path.

A generic solution with no breaking change: Add an optional property to the FetchInstrumentationConfig which is a function working similarly to the applyCustomAttributesOnSpan property, but accepts the name as an argument and returns a new name.

new FetchInstrumentation({
    decorateSpanName: (name: string, req: Request, res: Response) => string,

})

[raphael-theriault-swi]

You're correct that the span name shouldn't be prefixed with HTTP, but for client spans the behaviour of not including the target is correct, since that could result in a pretty high cardinality of span names. .

https://opentelemetry.io/docs/specs/semconv/http/http-spans/