CloudTraceSpanExporter+SimpleSpanProcessor+RequestsInstrumentor Infinite Loop

If you enable RequestsInstrumentor while using CloudTraceSpanExporter with SimpleSpanProcessor, you get an infinite loop on the first span exported.

When running locally, I see the following lines repeated with log level debug:

> I0206 10:03:10.286911 140694698043136 connectionpool.py:460] https://oauth2.googleapis.com:443 "POST /token HTTP/1.1" 200 None
> I0206 10:03:10.290570 140694689650432 requests.py:192] Making request: POST https://oauth2.googleapis.com/token

When running in cloud run, I see the following log entry repeated:

> http://metadata.google.internal:80 "GET /computeMetadata/v1/instance/service-accounts/default/?recursive=true HTTP/1.1" 200 615

Because of this I assume the issue is that a requests call is made during cloud trace export, which results in a span being recorded by the instrumentor and thus a new call to cloud trace export before the first one has complete auth set-up, resulting in new auth set-up and so on.

This blog post appears to document the same issue: https://minherz.medium.com/today-i-learned-why-using-opentelemetry-requestsinstrumentor-can-freeze-your-application-ae09410b016d

Because Cloud Run requires SimpleSpanProcessor, this essentially means RequestInstrumentor cannot be used in that environment.