fix(profiling): fix Lock dropping all samples when gevent monkey-patches

[vlad-scherbich]

Description

Bug

When gevent.monkey.patch_all (or patch_thread) runs after the profiler has started, it replaces threading's lock primitives in-place with gevent's cooperative lock types, destroying the profiler's _LockAllocatorWrapper. This causes the lock profiler to silently drop all lock profiling samples for the rest of the process lifetime.

This is a follow-up to the module-cloning bug fixed in PR #16775, where cleanup_loaded_modules re-imported threading; this bug is related to gevent's monkey-patching and is a separate code path that overwrites lock attributes after the re-import fix runs.

Fix

Adds a class-level hook on LockCollector that wraps gevent.monkey.patch_all and gevent.monkey.patch_thread with post-callbacks. After gevent finishes replacing lock types, the hook checks if any active collector's _LockAllocatorWrapper was overwritten and re-applies the profiler patch.

Testing

BEFORE

• no lock samples

AFTER

• lock samples visible

[cit-pr-commenter-54b7da]

Codeowners resolved as

ddtrace/profiling/collector/_lock.pyx                                   @DataDog/profiling-python
releasenotes/notes/fix-lock-profiler-gevent-monkey-patch-12dfaebf75e05535.yaml  @DataDog/apm-python
tests/profiling/collector/test_threading.py                             @DataDog/profiling-python

[datadog-prod-us1-5]

 

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⚠️ Warnings

🚦 8 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-py | build linux serverless: [arm64, cp315-cp315, v113741357-d2b8243-manylinux2014_aarch64, 1]     

🔧 Fix in code (Fix with Cursor).

NotImplementedError: This version of CPython is not supported yet.

DataDog/apm-reliability/dd-trace-py | build linux: [amd64, cp315-cp315, v113741238-d2b8243-manylinux2014_x86_64]     

🔧 Fix in code (Fix with Cursor).

NotImplementedError: This version of CPython is not supported yet

DataDog/apm-reliability/dd-trace-py | build linux serverless: [amd64, cp315-cp315, v113741238-d2b8243-manylinux2014_x86_64, 1]     

🛟 This job is unlikely to succeed on retry. Please review your pipeline configuration.

NotImplementedError: This version of CPython is not supported yet

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ℹ️ Info

No other issues found (see more)

🧪 All tests passed
❄️ No new flaky tests detected

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[pr-commenter]

Benchmarks

Benchmark execution time: 2026-05-26 03:58:39

Comparing candidate commit 7c996de in PR branch vlad/lock-fix-gevent-monkey-patched with baseline commit 1777513 in branch main.

Found 0 performance improvements and 5 performance regressions! Performance is the same for 617 metrics, 10 unstable metrics.

scenario:iastaspects-lstrip_aspect

• 🟥 execution_time [+71.356µs; +76.646µs] or [+25.749%; +27.659%]

scenario:iastaspects-translate_aspect

• 🟥 execution_time [+52.625µs; +59.714µs] or [+10.496%; +11.909%]

scenario:iastaspectsospath-ospathbasename_aspect

• 🟥 execution_time [+100.172µs; +110.350µs] or [+23.669%; +26.074%]

scenario:span-start

• 🟥 execution_time [+1.516ms; +1.663ms] or [+9.691%; +10.630%]

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

• 🟥 execution_time [+255.886ns; +298.012ns] or [+11.882%; +13.838%]

[chatgpt-codex-connector]

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[Copilot]

Pull request overview

Fixes a profiling reliability issue where gevent.monkey.patch_all() / patch_thread() can overwrite the lock-profiler’s patched lock allocators after the profiler is already running, causing lock samples to be dropped.

Changes:

• Add a LockCollector class-level mechanism to detect/wrap gevent.monkey.patch_all / patch_thread and re-apply lock patches if they were overwritten.
• Add subprocess tests that simulate gevent’s in-place replacement behavior (plus an optional integration test when gevent is available).
• Add a release note describing the fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
ddtrace/profiling/collector/_lock.pyx	Adds gevent monkey-patch wrapping and repatching logic tied to active lock collectors.
tests/profiling/collector/test_threading.py	Adds new subprocess tests simulating gevent lock replacement and verifying repatching behavior.
releasenotes/notes/fix-lock-profiler-gevent-monkey-patch-12dfaebf75e05535.yaml	Documents the fix in release notes.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.