chore: refactor SpanAggregator <> TraceWriter interface

[brettlangdon]

Help remove some implementation details from SpanAggregator into a the writer module.

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• 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
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[brettlangdon]

This is going to have conflicts with #13876

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/_trace/processor/__init__.py                                    @DataDog/apm-sdk-api-python
ddtrace/internal/ci_visibility/writer.py                                @DataDog/ci-app-libraries
ddtrace/internal/writer/__init__.py                                     @DataDog/apm-core-python
ddtrace/internal/writer/writer.py                                       @DataDog/apm-core-python
tests/utils.py                                                          @DataDog/python-guild

[brettlangdon]

I couldn't find a good way around this, since the value is coming from tracer.configure and not tied to a specific config option... we probably need to keep this until we can deprecate appsec_enabled from tracer.configure() :/

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 280 ± 3 ms.

The average import time from base is: 282 ± 2 ms.

The import time difference between this PR and base is: -1.6 ± 0.1 ms.

Import time breakdown

The following import paths have appeared:

ddtrace.auto 4.868 ms (1.74%)

ddtrace 4.868 ms (1.74%)

ddtrace.trace 4.868 ms (1.74%)

ddtrace._trace.filters 4.868 ms (1.74%)

ddtrace._trace.processor 4.868 ms (1.74%)

ddtrace.internal.writer 4.868 ms (1.74%)

ddtrace.internal.writer.writer 4.868 ms (1.74%)

ddtrace.internal.dogstatsd 4.868 ms (1.74%)

ddtrace.vendor.dogstatsd 4.579 ms (1.63%)

ddtrace.vendor.dogstatsd.base 4.316 ms (1.54%)

queue 1.363 ms (0.49%)

heapq 0.573 ms (0.20%)

_heapq 0.286 ms (0.10%)

_queue 0.298 ms (0.11%)

ddtrace.vendor.dogstatsd.context 0.787 ms (0.28%)

ddtrace.vendor.dogstatsd.context_async 0.470 ms (0.17%)

ddtrace.vendor.dogstatsd.container 0.565 ms (0.20%)

ddtrace.vendor.dogstatsd.format 0.326 ms (0.12%)

ddtrace.vendor.dogstatsd.route 0.277 ms (0.10%)

ddtrace.vendor.dogstatsd.compat 0.250 ms (0.09%)

The following import paths have disappeared:

ddtrace.auto 4.853 ms (1.73%)

ddtrace 4.853 ms (1.73%)

ddtrace.trace 4.853 ms (1.73%)

ddtrace._trace.filters 4.853 ms (1.73%)

ddtrace._trace.processor 4.853 ms (1.73%)

ddtrace.internal.dogstatsd 4.853 ms (1.73%)

ddtrace.vendor.dogstatsd 4.551 ms (1.62%)

ddtrace.vendor.dogstatsd.base 4.294 ms (1.53%)

queue 1.253 ms (0.45%)

heapq 0.574 ms (0.20%)

_heapq 0.288 ms (0.10%)

_queue 0.299 ms (0.11%)

ddtrace.vendor.dogstatsd.context 0.786 ms (0.28%)

ddtrace.vendor.dogstatsd.context_async 0.466 ms (0.17%)

ddtrace.vendor.dogstatsd.container 0.669 ms (0.24%)

ddtrace.vendor.dogstatsd.format 0.320 ms (0.11%)

ddtrace.vendor.dogstatsd.route 0.278 ms (0.10%)

ddtrace.vendor.dogstatsd.compat 0.251 ms (0.09%)

The following import paths have grown:

ddtrace.auto 0.020 ms (0.01%)

ddtrace 0.020 ms (0.01%)

ddtrace.trace 0.020 ms (0.01%)

ddtrace._trace.filters 0.020 ms (0.01%)

ddtrace._trace.processor 0.020 ms (0.01%)

ddtrace.internal.writer 0.020 ms (0.01%)

ddtrace.internal.writer.writer 0.020 ms (0.01%)

ddtrace.internal.sma 0.020 ms (0.01%)

The following import paths have shrunk:

ddtrace.auto 2.011 ms (0.72%)

ddtrace.bootstrap.sitecustomize 1.295 ms (0.46%)

ddtrace.bootstrap.preload 1.295 ms (0.46%)

ddtrace.internal.remoteconfig.client 0.646 ms (0.23%)

ddtrace 0.716 ms (0.26%)

ddtrace.trace 0.040 ms (0.01%)

ddtrace._trace.filters 0.040 ms (0.01%)

ddtrace._trace.processor 0.040 ms (0.01%)

ddtrace.internal._unpatched 0.030 ms (0.01%)

json 0.030 ms (0.01%)

json.decoder 0.030 ms (0.01%)

re 0.030 ms (0.01%)

enum 0.030 ms (0.01%)

types 0.030 ms (0.01%)

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-07-11 19:07:45

Comparing candidate commit a8f2f56 in PR branch LANGPLAT-134/abstract-writer-create with baseline commit c7c99b3 in branch main.

Found 0 performance improvements and 1 performance regressions! Performance is the same for 539 metrics, 2 unstable metrics.

scenario:iastaspects-replace_aspect

• 🟥 execution_time [+368.360ns; +571.703ns] or [+7.767%; +12.054%]

[VianneyRuhlmann]

LGTM, this will also be helpful for the DummyWriter creation with NativeWriter