feat(tracer): add configuration for connection mode

[Leiyks]

Description

Reviewer checklist

• Test coverage seems ok.
• Appropriate labels assigned.

[datadog-official]

⚠️ Tests

✨ Fix all issues with Cursor

⚠️ Warnings

❄️ 1 New flaky test detected

testDynamicRouteWithAllParametersGiven from laravel-8x-test.DDTrace\Tests\Integrations\Laravel\V8_x\PathParamsTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integrations\Laravel\V8_x\PathParamsTest::testDynamicRouteWithAllParametersGiven
Failed asserting that 0 matches expected 1.

tests/Integrations/Laravel/PathParamsTestSuite.php:19
tests/Common/RetryTraitVersionGeneric.php:28
phpvfscomposer://tests/vendor/phpunit/phpunit/phpunit:106

🧪 1032 Tests failed

    testSearchPhpBinaries from integration.DDTrace\Tests\Integration\PHPInstallerTest (Fix with Cursor)

    testSimplePushAndProcess from laravel-58-test.DDTrace\Tests\Integrations\Laravel\V5_8\QueueTest (Fix with Cursor)

testSimplePushAndProcess from laravel-8x-test.DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest (Datadog) (Fix with Cursor)

DDTrace\Tests\Integrations\Laravel\V8_x\QueueTest::testSimplePushAndProcess
Test code or tested code printed unexpected output: spanLinksTraceId: 6972513d00000000937e79bec9bc5269
tid: 6972513d00000000
hexProcessTraceId: 937e79bec9bc5269
hexProcessSpanId: 0a2ce579d6d74dc3
processTraceId: 10628066030976258665
processSpanId: 733213150812786115

View all

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: c59bfda | Docs | Datadog PR Page | Was this helpful? Give us feedback!}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 61.91%. Comparing base (4df27be) to head (c59bfda).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3573   +/-   ##
=======================================
  Coverage   61.91%   61.91%           
=======================================
  Files         140      140           
  Lines       13312    13312           
  Branches     1762     1762           
=======================================
  Hits         8242     8242           
  Misses       4280     4280           
  Partials      790      790           

---

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[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-01-22 16:18:20

Comparing candidate commit c59bfda in PR branch leiyks/sidecar-threaded-fallback with baseline commit 4df27be in branch master.

Found 0 performance improvements and 6 performance regressions! Performance is the same for 184 metrics, 4 unstable metrics.

scenario:MessagePackSerializationBench/benchMessagePackSerialization

• 🟥 execution_time [+6.518µs; +7.522µs] or [+6.342%; +7.320%]

scenario:MessagePackSerializationBench/benchMessagePackSerialization-opcache

• 🟥 execution_time [+4.731µs; +6.609µs] or [+4.757%; +6.645%]

scenario:SamplingRuleMatchingBench/benchRegexMatching1

• 🟥 execution_time [+70.712ns; +151.288ns] or [+5.972%; +12.778%]

scenario:SamplingRuleMatchingBench/benchRegexMatching2

• 🟥 execution_time [+76.550ns; +140.250ns] or [+6.548%; +11.997%]

scenario:SamplingRuleMatchingBench/benchRegexMatching3

• 🟥 execution_time [+73.958ns; +131.842ns] or [+6.291%; +11.214%]

scenario:SamplingRuleMatchingBench/benchRegexMatching4

• 🟥 execution_time [+93.434ns; +148.566ns] or [+8.073%; +12.836%]

[pr-commenter]

Benchmarks [ profiler ]

Benchmark execution time: 2026-01-14 16:24:26

Comparing candidate commit 05ebcae in PR branch leiyks/sidecar-threaded-fallback with baseline commit 88a859c in branch master.

Found 0 performance improvements and 2 performance regressions! Performance is the same for 28 metrics, 6 unstable metrics.

scenario:php-profiler-timeline-memory-with-profiler-and-timeline

• 🟥 cpu_user_time [+36.124ms; +78.620ms] or [+2.324%; +5.058%]
• 🟥 execution_time [+32.293ms; +51.335ms] or [+2.645%; +4.204%]

[bwoebi]

How does ASAN influence this? ASAN is supposed to run after MSHUTDOWN as well?
I suspect that is related to the timings and the fact that the libdatadog part doesn't properly handle shutdown currently.
And this should in fact always shutdown the sidecar in MSHUTDOWN.

[bwoebi]

Uhm, no? Just connect to the parents process socket? At least attempt to.

[bwoebi]

It is? Why?