feat: add injection metadata fields to telemetry forwarder

[sydney-tung]

Overview

This change adds additional fields to the telemetry forwarder used during injection. These fields will be used to add additional context that will be surfaced to the end user in the following Figma:

See Injection Metadata for more details.

Testing Strategy

I used this forwarder file to write output.json

#!/bin/bash


TELEMETRY_PAYLOAD=$(cat)

echo $TELEMETRY_PAYLOAD > /Users/sydney.tung/go/src/github.com/DataDog/sydney/output.json

I used this python app

#!/usr/bin/env python3

print("app complete")

I used this script

#!/bin/bash
[ -f /Users/sydney.tung/go/src/github.com/DataDog/sydney/output.json ] && rm /Users/sydney.tung/go/src/github.com/DataDog/sydney/output.json

export DD_APM_INSTRUMENTATION_DEBUG="true"        #injector debug logging 
export DD_INJECTION_ENABLED=true                                         #injecting enable & forwarding 
export DD_TRACE_DEBUG=true                                              #debug logging for dd-trace-py
export PYTHONPATH=/Users/sydney.tung/go/src/github.com/DataDog/dd-trace-py/lib-injection/sources:$PYTHONPATH   #path -> sitecustomize.py
export DD_TELEMETRY_FORWARDER_PATH=/Users/sydney.tung/go/src/github.com/DataDog/sydney/forwarder.sh                       #which forwarder excuted 
python3 /Users/sydney.tung/go/src/github.com/DataDog/sydney/app.py                                            #random app 

cat /Users/sydney.tung/go/src/github.com/DataDog/sydney/output.json | jq

This is a sample output

{
  "metadata": {
    "language_name": "python",
    "language_version": "3.13.3",
    "runtime_name": "cpython",
    "runtime_version": "3.13.3",
    "tracer_version": "unknown",
    "pid": 49533,
    "result": "unknown",
    "result_reason": "unknown",
    "result_class": "unknown"
  },
  "points": [
    {
      "name": "library_entrypoint.error",
      "tags": [
        "error_type:main_filenotfounderror"
      ]
    }
  ]
}

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/add-injection-metadata-fields-5f2d35cc9636c864.yaml  @DataDog/apm-python
lib-injection/sources/sitecustomize.py                                  @DataDog/apm-core-python

[brettlangdon]

merge conflict, but otherwise lgtm.

make sure to add a release note, e.g. reno new <slug>, the release note should be written to customers not to peer devs.

[github-actions]

Bootstrap import analysis

Comparison of import times between this PR and base.

Summary

The average import time from this PR is: 277 ± 4 ms.

The average import time from base is: 278 ± 3 ms.

The import time difference between this PR and base is: -1.3 ± 0.1 ms.

Import time breakdown

The following import paths have shrunk:

ddtrace.auto 1.948 ms (0.70%)

ddtrace.bootstrap.sitecustomize 1.273 ms (0.46%)

ddtrace.bootstrap.preload 1.273 ms (0.46%)

ddtrace.internal.remoteconfig.client 0.620 ms (0.22%)

ddtrace 0.675 ms (0.24%)

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: 2025-06-18 16:13:08

Comparing candidate commit a590aaa in PR branch sydney.tung/INPLAT-616-add-injection-metadata with baseline commit a4c9ba0 in branch main.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 559 metrics, 3 unstable metrics.

scenario:iastaspects-upper_aspect

• 🟥 execution_time [+193.518ns; +233.032ns] or [+8.592%; +10.347%]

scenario:telemetryaddmetric-1-gauge-metric-1-times

• 🟥 execution_time [+163.418ns; +239.341ns] or [+7.603%; +11.135%]

[brettlangdon]

just a few nits, then should be ready.

are there system tests that cover these new behaviors?

[brettlangdon]

this empty line is needed for style formatting

[betterengineering]

We may want to denote if this was forced. Something like success_forced?