fix(prebid-analytics): sample once per auction, not twice - #314
Merged
Conversation
samplingRate was applied at trackAuctionEnd and again in sendToWitnessAPI, each with an independent Math.random(), so the effective rate was rate^2 - 0.1 behaved as 0.01. This was latent while every tenant ran at 1.0, since shouldSample() short-circuits at >= 1. It surfaced when the sdk-bundles moved to 10%. Drop the second gate. trackAuctionEnd stores the decision on auction.sampled and the flush path already honours it.
juanli16
previously approved these changes
Aug 10, 2026
juanli16
reviewed
Aug 10, 2026
juanli16
approved these changes
Aug 10, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Why
samplingRatewas applied twice per auction — intrackAuctionEndand again insendToWitnessAPI— with independentMath.random()draws. Effective rate was rate², so 0.1 sampled at 1%.What Changed
addons/prebid/analytics: drop the sampling gate insendToWitnessAPI.trackAuctionEndalready stores the decision onauction.sampled, and both the flush andvisibilitychangepaths honour it.addons/prebid/analytics.test: thesamplingRate: 0case asserted the buggy contract, so it now expects the send to go through. Added a fractional-rate regression.How to Test
Tests added.
Notes