fix(profiling): stub ImportError collectors so the profiler can skip them

[vlad-scherbich]

Description

Delta vs #19269: adds optional Cython collector import stubs and a fallback so the profiler can skip collectors whose optional extensions are unavailable.

The fallback raises CollectorUnavailable when that collector is started; it does not hide missing native module errors, add the native build, or change asyncio behavior.

Layer	Meaning	Which PR
Compiled	Native prerequisite	#19269
Armed	Optional collector fallback	this PR
Observable	No standalone support claim	—

Testing

Risks

Additional Notes

changelog/no-changelog.

[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

[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.

.gitlab-ci.yml                                                          @DataDog/python-guild @DataDog/apm-core-python
.gitlab/templates/build-base-venvs.yml                                  @DataDog/python-guild @DataDog/apm-core-python
ddtrace/internal/datadog/profiling/cmake/FindLibNative.cmake            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/cmake/NativeHeaders.cmake            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/dd_wrapper/src/sample.cpp            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/ddup/CMakeLists.txt                  @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/CMakeLists.txt                 @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/echion/echion/cpython/tasks.h  @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/fuzz/CMakeLists.txt            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/src/echion/frame.cc            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/test/CMakeLists.txt            @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/test/test_cpython_layout_contracts.cpp  @DataDog/profiling-python
ddtrace/internal/datadog/profiling/stack/test/test_frame_state_315.cpp  @DataDog/profiling-python
ddtrace/profiling/collector/__init__.py                                 @DataDog/profiling-python
ddtrace/profiling/collector/asyncio.py                                  @DataDog/profiling-python
ddtrace/profiling/collector/exception.py                                @DataDog/profiling-python
ddtrace/profiling/collector/stack.py                                    @DataDog/profiling-python
ddtrace/profiling/collector/threading.py                                @DataDog/profiling-python
setup.py                                                                @DataDog/python-guild
tests/conftest.py                                                       @DataDog/python-guild
tests/profiling/collector/test_collector.py                             @DataDog/profiling-python
tests/profiling/test_profiler.py                                        @DataDog/profiling-python

[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.llmobs._integrations.llama_index -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=132)
ddtrace.llmobs._integrations.mcp -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=132)
ddtrace.llmobs._integrations.bedrock -×-> ddtrace.trace  (product:llmobs -> product:tracing, score=132)
ddtrace.llmobs._integrations.openai_agents -×-> 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

[datadog-prod-us1-5]

 

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⚠️ Warnings

❌ Your PR has failed checks. Please review the issues below and take necessary action before merging.

🚦 19 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-py | profiling/profile 11/23 — 🔧 Needs a code fix, caused by this PR

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DataDog/apm-reliability/dd-trace-py | profiling/profile 13/23 — 🔧 Needs a code fix, caused by this PR

View more details · View in GitLab

DataDog/apm-reliability/dd-trace-py | profiling_native_py315: [3.15, thread] — 🔧 Needs a code fix, caused by this PR

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View all 19 failed jobs.

ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

🔄 Datadog retried 15 tests - 3 passed on retry

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_{This comment will be updated automatically if new data arrives.
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[vlad-scherbich]

Revisit if becomes a problem

[pr-commenter]

Benchmarks

Benchmark execution time: 2026-09-09 21:03:09

Comparing candidate commit 5f2fb11 in PR branch vlad/315-profiling-collector-stubs with baseline commit 93fed02 in branch main.

📊 Benchmarking dashboard

Found 0 performance improvements and 1 performance regressions! Performance is the same for 532 metrics, 10 unstable metrics, 7 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:samplingrules-high_match

• 🟥 execution_time [+11.655µs; +14.014µs] or [+7.378%; +8.871%]

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 [-700.211ns; +762.390ns] or [-6.349%; +6.913%]

scenario:coreapiscenario-core_dispatch_1_listener

• unstable execution_time [-28.870ns; +37.251ns] or [-4.730%; +6.104%]

scenario:coreapiscenario-core_dispatch_50_listeners

• unstable execution_time [-1714.265ns; +1567.146ns] or [-10.035%; +9.174%]

scenario:coreapiscenario-core_dispatch_exception_listeners

• unstable execution_time [-1202.817ns; +1224.050ns] or [-9.205%; +9.368%]

scenario:coreapiscenario-core_dispatch_listeners

• unstable execution_time [-354.896ns; +303.938ns] or [-9.581%; +8.205%]

scenario:coreapiscenario-core_dispatch_no_args_listeners

• unstable execution_time [-257.880ns; +245.608ns] or [-8.796%; +8.377%]

scenario:coreapiscenario-core_dispatch_with_results_1_listener

• unstable execution_time [-54.659ns; +99.788ns] or [-4.775%; +8.717%]

scenario:coreapiscenario-core_dispatch_with_results_50_listeners

• unstable execution_time [-3987.506ns; +4121.776ns] or [-9.677%; +10.003%]

scenario:coreapiscenario-core_dispatch_with_results_listeners

• unstable execution_time [-735.124ns; +807.529ns] or [-9.061%; +9.953%]

scenario:packagesupdateimporteddependencies-import_many_stdlib_cached

• unstable execution_time [-61.008µs; +50.531µs] or [-10.386%; +8.603%]

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:httppropagationinject-ids_only

• 🟥 execution_time [+2.011µs; +2.201µs] or [+11.987%; +13.120%]

scenario:iastaspects-upper_noaspect

• 🟥 execution_time [+13.382µs; +16.523µs] or [+7.985%; +9.859%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+131.435µs; +137.906µs] or [+33.787%; +35.451%]

scenario:iastaspectssplit-rsplit_aspect

• 🟥 execution_time [+20.781µs; +24.651µs] or [+14.848%; +17.612%]

scenario:span-start

• 🟥 execution_time [+1.452ms; +1.571ms] or [+10.153%; +10.981%]

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

• 🟥 execution_time [+442.079ns; +484.139ns] or [+15.931%; +17.447%]

scenario:tracer-small

• 🟥 execution_time [+38.171µs; +41.036µs] or [+11.738%; +12.619%]

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-rstrip_aspect
• scenario:iastaspects-swapcase_aspect
• scenario:iastaspects-title_noaspect
• scenario:iastaspects-translate_aspect
• scenario:iastaspects-translate_noaspect
• scenario:packagespackageforrootmodulemapping-cache_off
• scenario:packagespackageforrootmodulemapping-cache_on
• scenario:sethttpmeta-all-enabled
• scenario:telemetryaddmetric-record-100-metrics