fix(config visibility): fix system test related to reporting of trace sampler and span sampler #272

anna-git · 2026-01-05T23:20:55Z

Description

Previous PR #268 accidentally broke the system test library_settings as we're not filling the telemetry vector with final.metadata anymore but from a separate array and this array wasn't passed by to finalize_config for span and trace sampler.

Motivation

Fix system test Test_Environment::test_library_settings

Additional Notes

Ran parametric tests locally and they all pass. (I thought they did with the previous PR as well but turned out I had a cached docker image)

https://datadoghq.atlassian.net/browse/APMAPI-1784

pr-commenter · 2026-01-05T23:21:59Z

Benchmarks

Benchmark execution time: 2026-01-07 13:46:24

Comparing candidate commit 5dec43d in PR branch anna/config-visibility-fix-sample-reporting with baseline commit ccc2a54 in branch main.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 1 metrics, 0 unstable metrics.

datadog-datadog-prod-us1 · 2026-01-05T23:27:31Z

🎯 Code Coverage
• Patch Coverage: 100.00%
• Overall Coverage: 87.81% (-0.03%)

View detailed report

_{This comment will be updated automatically if new data arrives.

🔗 Commit SHA: 5dec43d | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

codecov-commenter · 2026-01-05T23:28:11Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 87.80%. Comparing base (ccc2a54) to head (5dec43d).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #272      +/-   ##
==========================================
- Coverage   87.83%   87.80%   -0.03%     
==========================================
  Files          84       84              
  Lines        5664     5652      -12     
==========================================
- Hits         4975     4963      -12     
  Misses        689      689

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dmehala

The fix works as intended. That said, it will be cleaner to populate all_sources_configs by merging the configuration sources from the trace and span samplers using the results of finalize_config, leveraging the same mechanism used for metadata. This would help keep the approach consistent and easier to maintain.

dmehala · 2026-01-06T13:54:26Z

src/datadog/tracer_config.cpp

+  if (auto trace_sampler_config =
+          finalize_config(user_config.trace_sampler, &all_sources_configs)) {


I prefer the current behaviour where the configuration source/data are returned by finalize_config, then merged into the final all_sources_configs. Instead of adding a superfluous argument to finalize_config.

good point thank you, I got worried about creating a new hash table in these types, but in the end not changing signatures is definitely cleaner, I changed it in bcc8bd6

Also added a few more asserts in commit 5dec43d

dmehala

Thanks for addressing my comments. I’ve left a few additional comments that still need to be addressed; aside from those, LGTM.

dmehala · 2026-01-07T15:26:31Z

include/datadog/span_sampler_config.h

  };

  std::vector<Rule> rules;
  std::unordered_map<ConfigName, ConfigMetadata> metadata;


Since telemetry_configs already stores all versions, is this still necessary? If not, I recommend removing it and renaming telemetry_configs to metadata for clarity.

dmehala · 2026-01-09T10:40:10Z

src/datadog/span_sampler_config.cpp

  FinalizedSpanSamplerConfig result;
-
-  std::vector<SpanSamplerConfig::Rule> rules;
+  // Convert to Optional for resolve_and_record_config


These comments don’t provide long-term value and are unlikely to remain accurate over time. Can we remove it?

dmehala · 2026-01-09T10:43:15Z

src/datadog/trace_sampler_config.cpp

  // appended to the end of `rules`. First, though, we have to make sure the
  // sample rate is valid.
-  if (sample_rate) {
+  if (sample_rate && (env_config->sample_rate || config.sample_rate)) {


I’m not sure I understand why this is required. Could you provide some context?

anna-git temporarily deployed to dev January 5, 2026 23:21 — with GitHub Actions Inactive

anna-git changed the title ~~Config Visibility: fix reporting of trace sampler and span sampler~~ Config Visibility: fix system test related to reporting of trace sampler and span sampler Jan 5, 2026

anna-git temporarily deployed to dev January 5, 2026 23:24 — with GitHub Actions Inactive

Report trace sampler

8428f46

anna-git force-pushed the anna/config-visibility-fix-sample-reporting branch from 047a5b5 to 28c4f6d Compare January 5, 2026 23:34

anna-git had a problem deploying to dev January 5, 2026 23:35 — with GitHub Actions Failure

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anna-git marked this pull request as ready for review January 6, 2026 00:08

anna-git requested a review from a team as a code owner January 6, 2026 00:08

anna-git requested review from Anilm3 and removed request for a team January 6, 2026 00:08

dmehala changed the title ~~Config Visibility: fix system test related to reporting of trace sampler and span sampler~~ fix(config visibility): fix system test related to reporting of trace sampler and span sampler Jan 6, 2026

dmehala reviewed Jan 6, 2026

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anna-git force-pushed the anna/config-visibility-fix-sample-reporting branch from 46f073e to 7e00b6a Compare January 7, 2026 10:22

anna-git temporarily deployed to dev January 7, 2026 10:23 — with GitHub Actions Inactive

anna-git temporarily deployed to dev January 7, 2026 10:27 — with GitHub Actions Inactive

anna-git force-pushed the anna/config-visibility-fix-sample-reporting branch from 7e00b6a to e681579 Compare January 7, 2026 13:12

anna-git temporarily deployed to dev January 7, 2026 13:12 — with GitHub Actions Inactive

anna-git temporarily deployed to dev January 7, 2026 13:15 — with GitHub Actions Inactive

anna-git added 2 commits January 7, 2026 14:19

Report span sampler values

76721da

answer to comment, merge instead of passing by ref

bcc8bd6

anna-git force-pushed the anna/config-visibility-fix-sample-reporting branch from e681579 to 210bb3e Compare January 7, 2026 13:23

anna-git temporarily deployed to dev January 7, 2026 13:24 — with GitHub Actions Inactive

anna-git temporarily deployed to dev January 7, 2026 13:27 — with GitHub Actions Inactive

Add more asserts in unit tests

5dec43d

anna-git force-pushed the anna/config-visibility-fix-sample-reporting branch from 210bb3e to 5dec43d Compare January 7, 2026 13:43

anna-git temporarily deployed to dev January 7, 2026 13:44 — with GitHub Actions Inactive

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anna-git temporarily deployed to dev January 7, 2026 13:47 — with GitHub Actions Inactive

anna-git requested a review from dmehala January 8, 2026 10:31

dmehala approved these changes Jan 9, 2026

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		if (auto trace_sampler_config =
		finalize_config(user_config.trace_sampler, &all_sources_configs)) {

fix(config visibility): fix system test related to reporting of trace sampler and span sampler #272

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Description

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