Fix FlaskInstrumentor exemplars generation for http.server.(request.)duration #3912
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xrmx
reviewed
Nov 12, 2025
| # Get the span from wrapped_app_environ and re-create context manually | ||
| # to pass to histogram for exemplars generation | ||
| span = wrapped_app_environ.get(_ENVIRON_SPAN_KEY) | ||
| if span: |
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What do you think of doing something like metrics_context = context.set_value(_SPAN_KEY, span) if span else None and reuse the same record call to keep the code more compact?
emdneto
approved these changes
Nov 13, 2025
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Description
When exemplars are opted into via metrics SDK, this fixes FlaskInstrumentor generation of exemplars for
http.server.request.durationandhttp.server.duration(new and old semconv respectively) so trace ID and span ID are no longer empty.How? The metrics SDK implementation depends on its received OTel context being valid with a real span context inside it -- see ExemplarBucket.offer. Some metrics like these from FlaskInstrumentor don't have their values known until spans are complete and no longer in the current context, so metrics are recorded after spans ended. We now pass a new OTel context containing the Flask-stashed span.
Fixes #3913
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Does This PR Require a Core Repo Change?
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