fix(spans): Extract client sample rate from DSC for span v2 - #6299
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Dav1dde
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Aug 11, 2026
| fn inject_server_sample_rate( | ||
| /// Injects the client sample rate attribute into a span. Priority order: | ||
| /// attribute, DSC, 1.0 (default). | ||
| fn inject_client_sample_rate(attributes: &mut Annotated<Attributes>, dsc_sample_rate: Option<f64>) { |
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We have a normalization step to normalize the client sample rate, this runs after that normalization, basically bypassing it. I guess a better place would be to just extend the sample rate normalization to create it from the DSC if it doesn't already exist?
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Gotcha. Makes sense, I'll move it.
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@Dav1dde Two wrinkles that come from moving it:
- It ends up happening on every Relay and not just processing Relays. That means the first Relay in the chain will extract from DSC, and after that it'll be indistinguishable from a client setting it - we lose control of applying the logic (outdated customer relays will keep applying the old logic, unlike if we only did this during processing).
- This happens before trimming:
a. We're using up space budget/potentially causing more trimming of user data
b. Scarier, this attribute itself is subject to trimming
None of that applies to its current spot. Any thoughts/concerns about these?
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Currently span v2 (span streaming) spans are missing
sentry.client_sample_rateattributes. This value is used by Sentry to set the EAP trace item's client_sample_rate, which is used in EAP's extrapolation. This defaults all streaming spans to a client sample rate of 1.0, meaning extrapolation is frequently incorrect.If the client sample rate is missing from attributes, try to extract it from the DSC. For consistency, default it to 1.0 here if it's missing from both places.
Even though SDKs aren't expected to set
sentry.client_sample_rate, checking for an existing attribute value first means we can e.g. set it during the OTel -> Sentry span conversion (another case we're currently missing).Fixes RELAY-275.