See https://github.com/open-telemetry/opentelemetry-specification/blob/master/specification/data-semantic-conventions.md#http-server and https://github.com/open-telemetry/opentelemetry-python/blob/master/ext/opentelemetry-ext-wsgi/src/opentelemetry/ext/wsgi/__init__.py#L49-L56.

Even though the code seems right (apart from removing the query which should be included according to spec and adding a nonstandard http.host attribute), using a dumb flask example app (not the one from this repo, but that should work too), this resulted for me

Maybe there is a bogus value in one of the environment variables.

I will hopefully have time to investigate tomorrow, but if someone is quicker, fell free to take this issue.