perf(telemetry): remove call to importlib.metadata from get_module_distribution_versions

[taegyunkim]

TelemetryWriter periodically reports imported dependencies via calling get_module_distribution_versions() when new modules are imported. Typically when application is loaded up for the first time, the TelemetryWriter would notice new imports and then it calls with new module names. The function unnecessarily invoked importlib.metadata and replaced the usage with cached distribution name to version mapping.

See below for benchmark results.

Checklist

• 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
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• 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 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

[github-actions]

CODEOWNERS have been resolved as:

releasenotes/notes/perf-telemetry-d9881d20f22013f7.yaml                 @DataDog/apm-python
ddtrace/internal/debug.py                                               @DataDog/apm-core-python
ddtrace/internal/packages.py                                            @DataDog/apm-core-python
tests/internal/test_packages.py                                         @DataDog/apm-core-python

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 231 ± 2 ms.

The average import time from base is: 233 ± 2 ms.

The import time difference between this PR and base is: -2.12 ± 0.1 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.987 ms (0.86%)

ddtrace.bootstrap.sitecustomize 1.315 ms (0.57%)

ddtrace.bootstrap.preload 1.315 ms (0.57%)

ddtrace.internal.products 1.315 ms (0.57%)

ddtrace.internal.remoteconfig.client 0.633 ms (0.27%)

ddtrace 0.672 ms (0.29%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-04-25 20:32:57

Comparing candidate commit 58ec39a in PR branch taegyunkim/get_module_distribution_versions with baseline commit ea64efc in branch main.

Found 12 performance improvements and 0 performance regressions! Performance is the same for 459 metrics, 7 unstable metrics.

scenario:packagesupdateimporteddependencies-import_many

• 🟩 execution_time [-27.287ms; -27.173ms] or [-99.639%; -99.221%]

scenario:packagesupdateimporteddependencies-import_many_cached

• 🟩 execution_time [-27.649µs; -26.625µs] or [-18.732%; -18.038%]

scenario:packagesupdateimporteddependencies-import_many_stdlib

• 🟩 execution_time [-719.768ms; -716.565ms] or [-100.121%; -99.675%]

scenario:packagesupdateimporteddependencies-import_many_stdlib_cached

• 🟩 execution_time [-721.828ms; -718.239ms] or [-100.226%; -99.727%]

scenario:packagesupdateimporteddependencies-import_many_unknown

• 🟩 execution_time [-30.004ms; -29.874ms] or [-97.517%; -97.093%]

scenario:packagesupdateimporteddependencies-import_many_unknown_cached

• 🟩 execution_time [-249.124µs; -234.716µs] or [-24.140%; -22.744%]

scenario:packagesupdateimporteddependencies-import_one

• 🟩 execution_time [-11.347ms; -11.285ms] or [-100.101%; -99.551%]

scenario:packagesupdateimporteddependencies-import_one_cache

• 🟩 execution_time [-716.962ns; -640.755ns] or [-10.267%; -9.176%]

scenario:packagesupdateimporteddependencies-import_one_stdlib

• 🟩 execution_time [-10.385ms; -10.320ms] or [-100.132%; -99.508%]

scenario:packagesupdateimporteddependencies-import_one_stdlib_cache

• 🟩 execution_time [-649.793ns; -579.081ns] or [-9.411%; -8.387%]

scenario:packagesupdateimporteddependencies-import_one_unknown

• 🟩 execution_time [-19.777ms; -19.677ms] or [-100.026%; -99.519%]

scenario:packagesupdateimporteddependencies-import_one_unknown_cache

• 🟩 execution_time [-714.874ns; -663.700ns] or [-10.285%; -9.549%]