fix(di): dynamic function discovery fallback #13947
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We implement a dynamic function discovery fallback when the function-from-code resolution via the GC fails. This can happen if the target application has interacted with the GC, e.g. by freezing it at a time that will prevent the current discovery from being able to resolve the function from the referenced code object.
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Bootstrap import analysisComparison of import times between this PR and base. SummaryThe average import time from this PR is: 286 ± 6 ms. The average import time from base is: 297 ± 6 ms. The import time difference between this PR and base is: -11.3 ± 0.3 ms. Import time breakdownThe following import paths have grown:
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emmettbutler
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tylfin
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Pull Request Overview
This PR implements a dynamic fallback for function resolution when the GC-based lookup fails and updates the discovery logic to use it.
- Adds a private
_resolve_pairmethod that first triespair.resolve()and, onValueError, walks the module’s attributes to find the function. - Updates
by_nameto call_resolve_pairfor both direct and name-index lookups. - Includes a release note entry for the new fallback behavior.
Reviewed Changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| releasenotes/notes/fix-di-dynamic-discovery-fallback-3a5623e18584cd79.yaml | Adds a release note about the dynamic function discovery fallback. |
| ddtrace/debugging/_function/discovery.py | Introduces _resolve_pair and refactors by_name to leverage the fallback. |
BenchmarksBenchmark execution time: 2025-07-11 11:15:21 Comparing candidate commit 5f6c000 in PR branch Found 0 performance improvements and 2 performance regressions! Performance is the same for 546 metrics, 2 unstable metrics. scenario:iastaspects-replace_aspect
scenario:telemetryaddmetric-1-distribution-metric-1-times
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tylfin
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We implement a dynamic function discovery fallback when the function-from-code resolution via the GC fails. This can happen if the target application has interacted with the GC, e.g. by freezing it at a time that will prevent the current discovery from being able to resolve the function from the referenced code object. ## Testing Strategy The original issue was reproducible with a local deployment of [synapse](https://github.com/element-hq/synapse). The investigation led to the conclusion that the issue was caused by the way the application interacts with the GC https://github.com/element-hq/synapse/blob/1dc29563c1504a2523e467aa7bef6a7ac05cc60c/synapse/app/_base.py#L623C1-L629C35. Commenting out these lines makes the issue disappear. We have tested the fix against the unmodified application to verify that the proposed fix works. Refs: [DYNIS-28](https://datadoghq.atlassian.net/browse/DYNIS-28) ## Checklist - [x] PR author has checked that all the criteria below are met - The PR description includes an overview of the change - The PR description articulates the motivation for the change - The change includes tests OR the PR description describes a testing strategy - The PR description notes risks associated with the change, if any - Newly-added code is easy to change - The change follows the [library release note guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html) - The change includes or references documentation updates if necessary - Backport labels are set (if [applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)) ## Reviewer Checklist - [x] Reviewer has checked that all the criteria below are met - Title is accurate - All changes are related to the pull request's stated goal - Avoids breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes - Testing strategy adequately addresses listed risks - Newly-added code is easy to change - Release note makes sense to a user of the library - If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment - Backport labels are set in a manner that is consistent with the [release branch maintenance policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting) [DYNIS-28]: https://datadoghq.atlassian.net/browse/DYNIS-28?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ (cherry picked from commit b55f08f)
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We implement a dynamic function discovery fallback when the function-from-code resolution via the GC fails. This can happen if the target application has interacted with the GC, e.g. by freezing it at a time that will prevent the current discovery from being able to resolve the function from the referenced code object. ## Testing Strategy The original issue was reproducible with a local deployment of [synapse](https://github.com/element-hq/synapse). The investigation led to the conclusion that the issue was caused by the way the application interacts with the GC https://github.com/element-hq/synapse/blob/1dc29563c1504a2523e467aa7bef6a7ac05cc60c/synapse/app/_base.py#L623C1-L629C35. Commenting out these lines makes the issue disappear. We have tested the fix against the unmodified application to verify that the proposed fix works. Refs: [DYNIS-28](https://datadoghq.atlassian.net/browse/DYNIS-28) ## Checklist - [x] PR author has checked that all the criteria below are met - The PR description includes an overview of the change - The PR description articulates the motivation for the change - The change includes tests OR the PR description describes a testing strategy - The PR description notes risks associated with the change, if any - Newly-added code is easy to change - The change follows the [library release note guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html) - The change includes or references documentation updates if necessary - Backport labels are set (if [applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)) ## Reviewer Checklist - [x] Reviewer has checked that all the criteria below are met - Title is accurate - All changes are related to the pull request's stated goal - Avoids breaking [API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces) changes - Testing strategy adequately addresses listed risks - Newly-added code is easy to change - Release note makes sense to a user of the library - If necessary, author has acknowledged and discussed the performance implications of this PR as reported in the benchmarks PR comment - Backport labels are set in a manner that is consistent with the [release branch maintenance policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting) [DYNIS-28]: https://datadoghq.atlassian.net/browse/DYNIS-28?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ (cherry picked from commit b55f08f)
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We implement a dynamic function discovery fallback when the function-from-code resolution via the GC fails. This can happen if the target application has interacted with the GC, e.g. by freezing it at a time that will prevent the current discovery from being able to resolve the function from the referenced code object.
Testing Strategy
The original issue was reproducible with a local deployment of synapse. The investigation led to the conclusion that the issue was caused by the way the application interacts with the GC https://github.com/element-hq/synapse/blob/1dc29563c1504a2523e467aa7bef6a7ac05cc60c/synapse/app/_base.py#L623C1-L629C35. Commenting out these lines makes the issue disappear. We have tested the fix against the unmodified application to verify that the proposed fix works.
Refs: DYNIS-28
Checklist
Reviewer Checklist