fix(profiling): invalidate stale Echion frames on Python 3.14 - #19641
fix(profiling): invalidate stale Echion frames on Python 3.14#19641taegyunkim wants to merge 4 commits into
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🎉 All green!🧪 All tests passed 🔗 Commit SHA: 7340e29 | Docs | Datadog PR Page | Give us feedback! |
BenchmarksBenchmark execution time: 2026-08-11 23:12:51 Comparing candidate commit 93e735b in PR branch Found 0 performance improvements and 6 performance regressions! Performance is the same for 606 metrics, 10 unstable metrics. scenario:httppropagationinject-ids_only
scenario:iastaspects-add_aspect
scenario:iastaspectsospath-ospathbasename_aspect
scenario:span-start
scenario:telemetryaddmetric-1-count-metric-1-times
scenario:tracer-small
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taegyunkim
changed the title
…ode-generation # Conflicts: # ddtrace/internal/datadog/profiling/stack/test/test_sampling_cycle_state.cpp
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Pull request overview
Prevents stale Echion frame attribution on Python 3.14 by tracking interpreter code-object generations and invalidating frame identity caches.
Changes:
- Captures interpreter generation snapshots before stack sampling.
- Clears frame and asyncio/uvloop identity caches when generations change or snapshots are incomplete.
- Adds native and Python regression coverage plus release notes.
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
tests/profiling/collector/test_stack.py |
Tests code-object address reuse. |
releasenotes/notes/profiling-echion-code-generation-6df0c11c31a5d70c.yaml |
Documents the fix. |
ddtrace/internal/datadog/profiling/stack/test/test_sampling_cycle_state.cpp |
Tests generation-based invalidation. |
ddtrace/internal/datadog/profiling/stack/src/sampler.cpp |
Captures snapshots before unwinding. |
ddtrace/internal/datadog/profiling/stack/src/echion/interp.cc |
Reads generations and reports snapshot completeness. |
ddtrace/internal/datadog/profiling/stack/include/sampler.hpp |
Adds interpreter snapshot storage. |
ddtrace/internal/datadog/profiling/stack/fuzz/fuzz_echion_interp.cpp |
Adapts the fuzz harness to the new return value. |
ddtrace/internal/datadog/profiling/stack/echion/echion/interp.h |
Extends interpreter metadata and traversal API. |
ddtrace/internal/datadog/profiling/stack/echion/echion/echion_sampler.h |
Implements cache invalidation and fork reset behavior. |
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Pull request overview
Copilot reviewed 9 out of 9 changed files in this pull request and generated no new comments.
Suppressed comments (1)
tests/profiling/collector/test_stack.py:193
- The regression does not prove that the old function was sampled before its code object is released. If the sampler misses this first execution window but samples the replacement, both final assertions pass even with generation invalidation disabled because no stale cache entry was ever created. Inspect the profile emitted here and require
old_nameto be present before proceeding.
ddup.upload()
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Codex Review: Didn't find any major issues. Bravo. Reviewed commit: ℹ️ About Codex in GitHubYour team has set up Codex to review pull requests in this repo. Reviews are triggered when you
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Description
On Python 3.14, Echion's frame cache can return stale metadata when CPython reuses a released code object's address. Before each sampling cycle, snapshot every interpreter's
(interpreter ID, code object generation). If that snapshot changes, clear the global frame cache and the cached asyncio and uvloop frame identities before unwinding stacks.If the interpreter snapshot is incomplete, clear the same state and skip that sampling cycle. This preserves Echion's existing multi-interpreter traversal, including processes that host a legacy subinterpreter without importing ddtrace there.
Python 3.13 and earlier are unchanged because they do not expose
_code_object_generation.Testing
mainat6f2816b8eand rebuilt the Python 3.14 native extension with warnings as errors.git diff --check, and the profiling native coverage check.Risks
Workloads that frequently create code objects will clear Echion's frame cache more often. The invalidation is limited to Python 3.14 and keeps the existing cache structure and sampling behavior otherwise unchanged.
An unreadable or inconsistent interpreter snapshot skips one cycle rather than risking stale frame attribution.
The generation snapshot is intentionally lock-free and taken once per sampling cycle. Code-object deletion after that snapshot can leave frame metadata stale for the remainder of the current cycle; the next cycle observes the generation change and clears the cache. Eliminating this bounded race would require additional per-frame synchronization or identity tracking that is outside this change.
Additional Notes
This intentionally does not add per-interpreter frame caches, change frame-cache keys, or add code watchers for older Python versions.
Pre-review checklist