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 BitsAI or with Cursor

⚠️ Warnings

❄️ 4 New flaky tests detected

tmp/build_extension/tests/ext/background-sender/sidecar_thread_mode_permissions.phpt (Thread mode sidecar: uses abstract Unix socket (no filesystem permissions needed)) from PHP.tmp.build_extension.tests.ext.background.sender (Datadog) (Fix with Cursor)

001+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
     Sidecar uses abstract socket

tmp/build_extension/tests/ext/pcntl/pcntl_fork_thread_mode_orphan.phpt (Thread mode sidecar: orphaned child process promotes itself to master after parent exits) from PHP.tmp.build_extension.tests.ext.pcntl (Datadog) (Fix with Cursor)

001+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
002+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
     Child span submitted

tmp/build_extension/tests/ext/background-sender/sidecar_thread_mode_permissions.phpt (Thread mode sidecar: uses abstract Unix socket (no filesystem permissions needed)) from php.tmp.build_extension.tests.ext.background.sender (Datadog) (Fix with Cursor)

001+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
     Sidecar uses abstract socket

tmp/build_extension/tests/ext/pcntl/pcntl_fork_thread_mode_orphan.phpt (Thread mode sidecar: orphaned child process promotes itself to master after parent exits) from php.tmp.build_extension.tests.ext.pcntl (Datadog) (Fix with Cursor)

001+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
002+ [ddtrace] [error] There is no user-span on the top of the stack. Cannot close.
     Child span submitted

View all

🧪 1038 Tests failed

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

DDTrace\Tests\Integration\PHPInstallerTest::testSearchPhpBinaries
Test code or tested code printed unexpected output: Searching for available php binaries, this operation might take a while.

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

DDTrace\Tests\Integrations\Laravel\V5_8\QueueTest::testSimplePushAndProcess
Test code or tested code printed unexpected output: spanLinksTraceId: 69a9991a00000000833980d0afec726a
tid: 69a9991a00000000
hexProcessTraceId: 833980d0afec726a
hexProcessSpanId: e1f6a564226de103
processTraceId: 9455730526434128490
processSpanId: 16282383352297545987

phpvfscomposer://tests/vendor/phpunit/phpunit/phpunit:106

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: 69a9992e0000000092707456a55091d0
tid: 69a9992e00000000
hexProcessTraceId: 92707456a55091d0
hexProcessSpanId: f97a3264a6192835
processTraceId: 10552061842418602448
processSpanId: 17976736270467541045

View all

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: 8b7a5b3 | Docs | Datadog PR Page | Was this helpful? React with 👍/👎 or give us feedback!}

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.08%. Comparing base (8cd0131) to head (8b7a5b3).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3573      +/-   ##
==========================================
- Coverage   62.22%   62.08%   -0.14%     
==========================================
  Files         141      141              
  Lines       13352    13352              
  Branches     1746     1746              
==========================================
- Hits         8308     8290      -18     
- Misses       4253     4269      +16     
- Partials      791      793       +2     

see 4 files with indirect coverage changes

---

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[pr-commenter]

Benchmarks [ tracer ]

Benchmark execution time: 2026-03-05 16:01:30

Comparing candidate commit 8b7a5b3 in PR branch leiyks/sidecar-threaded-fallback with baseline commit 8cd0131 in branch master.

Found 0 performance improvements and 3 performance regressions! Performance is the same for 188 metrics, 3 unstable metrics.

scenario:ComposerTelemetryBench/benchTelemetryParsing-opcache

• 🟥 execution_time [+0.977µs; +1.823µs] or [+7.940%; +14.824%]

scenario:PHPRedisBench/benchRedisBaseline-opcache

• 🟥 execution_time [+3.380µs; +5.054µs] or [+2.425%; +3.626%]

scenario:SamplingRuleMatchingBench/benchRegexMatching4-opcache

• 🟥 execution_time [+275.822ns; +509.578ns] or [+2.486%; +4.592%]

[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%]