aiohttp-client: Allow overriding of span status

[nils-borrmann-y42]

Version 0.34b0

In the aiohttp-client instrumentation, the response_hook is called before setting the status and the status_code of the span. This means the user cannot set a custom status on the span, as it will be immediately overridden by the default value.

In my specific usecase I am making requests as a cache, where a cache-miss returns a 404 response. These spans are than tagged with the StatusCode.ERROR, which is a bit annoying to me as these responses are completely expected and accepted. Therefore I would like to override the StatusCode on those requests in the response_hook.

I am happy to provide a fix for this.

What is the expected behavior?
reponse_hook should be called after setting the span status, to allow for overriding it.

What is the actual behavior?
reponse_hook is called before setting the span status

Additional context
I compared this with the httpx and requests instrumentation. In those instrumentations, overriding the status in the hook is possible.

[srikanthccv]

It's because the semantic conventions enforce it for the HTTP clients https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#status.

[nils-borrmann-y42]

It's because the semantic conventions enforce it for the HTTP clients open-telemetry/opentelemetry-specification@main/specification/trace/semantic_conventions/http.md#status.

Which is fine, but otel could still let the user decide to override it in specific cases (which is what most other implementations already do).