ci(testrunner): rebuild 3.15-dev and pin Cython<3.3 on the 3.15 cache (PROF-14439)

[vlad-scherbich]

Description

Delta vs #19903.

docker/Dockerfile: pyenv v2.6.31 → v2.8.4. A docker/** push to main retriggers .github/workflows/testrunner.yml and recompiles 3.15-dev. Does not pin a 3.15.0 interpreter or the GitLab TESTRUNNER_IMAGE digest.

.cached_testrunner EXT_CACHE_VENV: pip install … 'Cython<3.3' when PYTHON_VERSION=3.15; other versions stay unpinned Cython.

If this merges and nothing else new lands: the next testrunner image rebuilds with pyenv 2.8.4, and the 3.15 cache venv gets Cython 3.2.x. GitLab jobs keep the old digest until a follow-up pins it.

Testing

Image rebuild is the testrunner workflow after merge to main. After publish, pin .gitlab/testrunner.yml. Confirm the generated 3.15 build_base_venvs before_script installs Cython<3.3.

Risks

Pyenv 2.8.4 also reinstalls 3.8–3.14 (patch-level bumps possible). Cython pin is 3.15-only.

Additional Notes

Does not duplicate #19861 (pyproject.toml unchanged). No release note: CI chore, changelog/no-changelog.

Base: #19903. Next: #19904.

[cit-pr-commenter-54b7da]

Codeowners resolved as

Resolved from the full PR diff against main using the target branch CODEOWNERS file.
CODEOWNERS team requests not listed below are not required by the current file set.

No remaining files require a CODEOWNERS review.

[cit-pr-commenter-54b7da]

Dependency direction analysis

⚠️ Existing dependency direction violations

There are 230 dependency direction violations that already exist on the base branch and have not been changed by this PR.

Show existing violations (showing 5 of 230 highest severity)

ddtrace.internal.tracemethods -×-> ddtrace.trace  (internal-core -> product:tracing, score=134)
ddtrace.internal.ci_visibility.api._base -×-> ddtrace.trace  (product:ci_visibility -> product:tracing, score=132)
ddtrace.appsec._listeners -×-> ddtrace.trace  (product:appsec -> product:tracing, score=132)
ddtrace.llmobs._integrations.pydantic_ai -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=132)
ddtrace.llmobs._integrations.openai -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=132)

To see all violations, download the layers-base.json and layers-pr.json artifacts from this CI job and run:

uv run --script scripts/import-analysis/layers.py compare layers-base.json layers-pr.json

[cit-pr-commenter-54b7da]

Circular import analysis

⚠️ Existing circular imports

There are 3 circular imports that already exist on the base branch and have not been changed by this PR.

ddtrace.llmobs -> ddtrace.llmobs._evaluators -> ddtrace.llmobs._evaluators.format -> ddtrace.llmobs._experiment -> ddtrace.llmobs
ddtrace.errortracking._handled_exceptions.bytecode_injector -> ddtrace.errortracking._handled_exceptions.callbacks -> ddtrace.errortracking._handled_exceptions.collector -> ddtrace.errortracking._handled_exceptions.bytecode_reporting -> ddtrace.errortracking._handled_exceptions.bytecode_injector
ddtrace.appsec._asm_request_context -> ddtrace.appsec._iast._iast_request_context_base -> ddtrace.appsec._iast._iast_env -> ddtrace.appsec._iast.reporter -> ddtrace.appsec._exploit_prevention.stack_traces -> ddtrace.appsec._asm_request_context

[datadog-datadog-prod-us1-2]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: a77787f | Docs | View more details | Give us feedback!}

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-09-02 02:25:08

Comparing candidate commit a77787f in PR branch vlad/py315-testrunner-cython-pin with baseline commit a78b774 in branch main.

📊 Benchmarking dashboard

Found 0 performance improvements and 7 performance regressions! Performance is the same for 577 metrics, 10 unstable metrics, 1 known flaky benchmarks, 17 flaky benchmarks without significant changes.

Explanation

This is an A/B test comparing a candidate commit's performance against that of a baseline commit. Performance changes are noted in the tables below as:

• 🟩 = significantly better candidate vs. baseline
• 🟥 = significantly worse candidate vs. baseline

We compute a confidence interval (CI) over the relative difference of means between metrics from the candidate and baseline commits, considering the baseline as the reference.

If the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD), the change is considered significant.

Feel free to reach out to #apm-benchmarking-platform on Slack if you have any questions.

More details about the CI and significant changes

You can imagine this CI as a range of values that is likely to contain the true difference of means between the candidate and baseline commits.

CIs of the difference of means are often centered around 0%, because often changes are not that big:

---------------------------------(------|---^--------)-------------------------------->
                              -0.6%    0%  0.3%     +1.2%
                                 |          |        |
         lower bound of the CI --'          |        |
sample mean (center of the CI) -------------'        |
         upper bound of the CI ----------------------'

As described above, a change is considered significant if the CI is entirely outside the configured SIGNIFICANT_IMPACT_THRESHOLD (or the deprecated UNCONFIDENCE_THRESHOLD).

For instance, for an execution time metric, this confidence interval indicates a significantly worse performance:

----------------------------------------|---------|---(---------^---------)---------->
                                       0%        1%  1.3%      2.2%      3.1%
                                                  |   |         |         |
       significant impact threshold --------------'   |         |         |
                      lower bound of CI --------------'         |         |
       sample mean (center of the CI) --------------------------'         |
                      upper bound of CI ----------------------------------'

scenario:httppropagationextract-tracecontext_headers

• 🟥 execution_time [+2.297µs; +2.524µs] or [+7.222%; +7.938%]

scenario:httppropagationinject-ids_only

• 🟥 execution_time [+1.772µs; +1.897µs] or [+10.854%; +11.625%]

scenario:iastaspects-rstrip_aspect

• 🟥 execution_time [+69.170µs; +75.908µs] or [+18.041%; +19.799%]

scenario:iastaspects-stringio_noaspect

• 🟥 execution_time [+23.984µs; +27.953µs] or [+7.250%; +8.449%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+113.997µs; +120.768µs] or [+28.871%; +30.586%]

scenario:telemetryaddmetric-1-count-metric-1-times

• 🟥 execution_time [+388.535ns; +430.794ns] or [+14.635%; +16.226%]

scenario:tracer-small

• 🟥 execution_time [+42.776µs; +44.759µs] or [+13.323%; +13.940%]

Unstable benchmarks

These benchmarks have a confidence interval too wide to call a change; treat them as noise rather than signal.

scenario:coreapiscenario-context_with_data_listeners

• unstable execution_time [-713.208ns; +765.517ns] or [-6.497%; +6.973%]

scenario:coreapiscenario-core_dispatch_1_listener

• unstable execution_time [-33.612ns; +35.381ns] or [-5.416%; +5.701%]

scenario:coreapiscenario-core_dispatch_50_listeners

• unstable execution_time [-1713.802ns; +1628.532ns] or [-9.919%; +9.425%]

scenario:coreapiscenario-core_dispatch_exception_listeners

• unstable execution_time [-1178.705ns; +1282.420ns] or [-9.143%; +9.947%]

scenario:coreapiscenario-core_dispatch_listeners

• unstable execution_time [-332.523ns; +327.927ns] or [-8.946%; +8.822%]

scenario:coreapiscenario-core_dispatch_no_args_listeners

• unstable execution_time [-257.140ns; +260.186ns] or [-8.702%; +8.805%]

scenario:coreapiscenario-core_dispatch_with_results_1_listener

• unstable execution_time [-75.075ns; +76.227ns] or [-6.367%; +6.465%]

scenario:coreapiscenario-core_dispatch_with_results_50_listeners

• unstable execution_time [-3883.244ns; +4065.163ns] or [-9.530%; +9.976%]

scenario:coreapiscenario-core_dispatch_with_results_listeners

• unstable execution_time [-789.141ns; +746.990ns] or [-9.728%; +9.208%]

scenario:packagesupdateimporteddependencies-import_many_stdlib_cached

• unstable execution_time [-63.383µs; +55.959µs] or [-10.040%; +8.864%]

Known flaky benchmarks

These benchmarks are marked as flaky and will not trigger a failure. Modify FLAKY_BENCHMARKS_REGEX to control which benchmarks are marked as flaky.

scenario:span-start

• 🟥 execution_time [+1.764ms; +2.013ms] or [+12.987%; +14.823%]

Known flaky benchmarks without significant changes:

• scenario:errortrackingflasksqli-baseline
• scenario:flasksimple-iast-get
• scenario:iastaspects-casefold_aspect
• scenario:iastaspects-casefold_noaspect
• scenario:iastaspects-index_aspect
• scenario:iastaspects-ljust_noaspect
• scenario:iastaspects-lower_aspect
• scenario:iastaspects-replace_aspect
• scenario:iastaspects-swapcase_aspect
• scenario:iastaspects-title_noaspect
• scenario:iastaspects-translate_aspect
• scenario:iastaspects-translate_noaspect
• scenario:iastaspects-upper_noaspect
• scenario:packagespackageforrootmodulemapping-cache_off
• scenario:packagespackageforrootmodulemapping-cache_on
• scenario:sethttpmeta-all-enabled
• scenario:telemetryaddmetric-record-100-metrics

[Copilot]

Pull request overview

This PR updates the GitLab CI build_base_venvs template (.cached_testrunner) to avoid installing Cython 3.3.x into the EXT_CACHE_VENV when running the Python 3.15 arm, because Cython 3.3.0’s cp315 wheel can segfault on pre-rc1 Python 3.15 interpreters. This keeps the base-venv cache bootstrapping stable on 3.15 while leaving 3.9–3.14 behavior unchanged.

Changes:

• Add a PYTHON_VERSION == 3.15 conditional in .cached_testrunner to install Cython<3.3 only for the 3.15 venv cache.
• Preserve the existing unpinned Cython install path for Python 3.9–3.14.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[vlad-scherbich]

/merge -m squash

[gh-worker-devflow-routing-ef8351]

View all feedbacks in Devflow UI.

2026-09-02 02:10:50 UTC ℹ️ Start processing command /merge -m squash

---

2026-09-02 02:11:08 UTC ℹ️ MergeQueue: Pull request is not mergeable yet

It will be processed automatically as soon as GitHub reports it as mergeable. View in MergeQueue UI.

• Run /code blockers to see what is blocking it.
• Run /remove to cancel it.

---

2026-09-02 02:29:12 UTC ℹ️ MergeQueue: merge request added to the queue

The expected merge time in main is approximately 1h (p90).

---

2026-09-02 03:06:39 UTC ℹ️ MergeQueue: This merge request was merged