Fix Single Span Sampling for parent spans#4674
Merged
Merged
Conversation
…ate from a trace sampling priority, so child spans will be dropped even if the parent span is kept by SSS.
3 tasks
bantonsson
approved these changes
Feb 7, 2023
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
What Does This Do
Fix Single Span Sampling for root spans to keep an SSS decision separate from a trace sampling priority, so child spans will be dropped when the entire trace has to be dropped even if the parent span is kept by SSS.
Motivation
Fix for when a root span is sampled by the single span sampling but the entire span is dropped.
The problem is that when a span doesn’t have an explicitly set sampling priority then it gets it from the root span context. It’s done to preserve a sampling priority in case of partial flush (#3412). This logic was implemented before single span sampling was introduced.
Now, when a root span is sampled by the single span sampling mechanism, it overrides the already set dropping priority causing a child span (without priority -128) to use a single span sampling priority instead of a trace dropping priority that has been set for the entire trace.
Additional Notes
Relevant System Tests PR
incident-18687