OTel span events may drop None-valued attributes with a warning #171

_emit_event passes the attributes dict to span.add_event unchanged. Some events can carry None values, for example last_status on retry.giving_up when the last attempt raised instead of returning a response (src/httpware/middleware/resilience/retry.py). The OpenTelemetry SDK does not accept None as an attribute value. As far as I know it drops the attribute and logs a warning, which would mean one warning on every such give-up.

This was not run end to end: the OTel SDK is not installed in the dev environment.

How to confirm: install opentelemetry-sdk, set up a TracerProvider with an in-memory exporter, start a span, and drive a Retry to give up on a raised NetworkError. Check whether the SDK logs a warning and whether last_status is missing from the recorded event.

If it reproduces, the fix is to drop None values from the span-event attributes in _emit_event and keep them in the log record.