[frontend] fix http.status_code on error

[puckpuck]

Fixes: #749

The http.status_code for synthetic requests to the frontend, was being set at span creation time. This changes that to set it just before the span ends. Looks like the app.frontend.requests metric was also affected by this issue.

Also removed some duplicated error handling code.

[julianocosta89]

When testing it I started getting some errors in the logs like this:

frontend                 | Can not execute the operation on ended Span {traceId: 9a72857f7ceef2b0e3a7856e0856e4e7, spanId: 214218836dea381f}
frontend                 | You can only call end() on a span once.

Besides that, it looks good to me.

[puckpuck]

When testing it I started getting some errors in the logs like this:

frontend                 | Can not execute the operation on ended Span {traceId: 9a72857f7ceef2b0e3a7856e0856e4e7, spanId: 214218836dea381f}
frontend                 | You can only call end() on a span once.

Besides that, it looks good to me.

I do not see that error at all. I remember seeing it in the past, but trying again from main and this PR's branch, I can't reproduce it.

[martinkuba]

I am seeing the Can not execute the operation on ended Span error as well. It looks like it is this line. It is happening on the main branch for me as well. I think it makes sense since the span is from the http instrumentation when the site is NOT running in synthetic mode. I am guessing we just never noticed this before? The fix would be to end the span manually only when it is also created in this same file.

[puckpuck]

Oh, I see. It only happens when you access the app from a browser UI (non-synthetic requests).

Yeah, I can plug in some logic to only close if we created it. Will update the PR later today.

[puckpuck]

Updated the PR to only end the span when it's the one that we create to split synthetic requests.

[julianocosta89]

Awesome! 🤩

[cartersocha]

Can you add a changelog item please