Support automated sidecar fallback via threads (#3455)

[Leiyks]

Description

Use threads to connect to the sidecar

Libdatadog PR

Related Jiras: APMLP-478

[pr-commenter[bot]]

Benchmarks [ profiler ]

Benchmark execution time: 2025-10-31 21:30:09

Comparing candidate commit bcf647e31fce5769efa15f94934258cb591c57e7 in PR branch leiyks/sidecar-thread-connection with baseline commit 3456dec3802cbe0c16229b118561269b48f55c8d in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 29 metrics, 7 unstable metrics.

[codecov-commenter]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 61.77%. Comparing base (8a6a038) to head (7efee66). :warning: Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3468      +/-   ##
==========================================
- Coverage   61.79%   61.77%   -0.02%     
==========================================
  Files         142      142              
  Lines       12904    12904              
  Branches     1689     1689              
==========================================
- Hits         7974     7972       -2     
- Misses       4169     4172       +3     
+ Partials      761      760       -1     

see 1 file with indirect coverage changes

---

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Benchmarks [ tracer ]

Benchmark execution time: 2025-11-24 13:01:16

Comparing candidate commit 7efee66bb1635eb09c48e3898cdc89af27ded4bb in PR branch leiyks/sidecar-thread-connection with baseline commit 8a6a0381abea717339d8939ca001c5bac843599a in branch master.

Found 3 performance improvements and 15 performance regressions! Performance is the same for 166 metrics, 10 unstable metrics.

scenario:ContextPropagationBench/benchInject64Bit

• 🟥 execution_time [+11.298µs; +11.466µs] or [+583.279%; +591.941%]

scenario:MessagePackSerializationBench/benchMessagePackSerialization

• 🟥 execution_time [+4.710µs; +6.110µs] or [+4.632%; +6.008%]

scenario:PDOBench/benchPDOOverhead

• 🟥 execution_time [+15.042µs; +20.484µs] or [+6.740%; +9.178%]

scenario:PDOBench/benchPDOOverhead-opcache

• 🟥 execution_time [+15.400µs; +20.924µs] or [+6.932%; +9.419%]

scenario:PDOBench/benchPDOOverheadWithDBM

• 🟥 execution_time [+20.442µs; +25.810µs] or [+9.214%; +11.633%]

scenario:PDOBench/benchPDOOverheadWithDBM-opcache

• 🟥 execution_time [+17.266µs; +21.795µs] or [+7.827%; +9.880%]

scenario:PHPRedisBench/benchRedisOverhead

• 🟥 execution_time [+177.756µs; +247.580µs] or [+20.301%; +28.275%]

scenario:PHPRedisBench/benchRedisOverhead-opcache

• 🟥 execution_time [+185.201µs; +252.912µs] or [+20.350%; +27.791%]

scenario:SamplingRuleMatchingBench/benchRegexMatching2-opcache

• 🟥 execution_time [+10.007µs; +10.113µs] or [+708.228%; +715.737%]

scenario:SpanBench/benchOpenTelemetryAPI

• 🟥 execution_time [+119.413µs; +153.573µs] or [+16.627%; +21.384%]
• 🟥 mem_peak [+1.717MB; +1.720MB] or [+4.157%; +4.163%]

scenario:SpanBench/benchOpenTelemetryAPI-opcache

• 🟥 execution_time [+105.837µs; +121.669µs] or [+15.993%; +18.385%]

scenario:SpanBench/benchOpenTelemetryInteroperability

• 🟥 execution_time [+120.823µs; +132.850µs] or [+65.504%; +72.024%]

scenario:SpanBench/benchOpenTelemetryInteroperability-opcache

• 🟥 execution_time [+115.222µs; +125.921µs] or [+67.485%; +73.752%]

scenario:TraceFlushBench/benchFlushTrace

• 🟩 execution_time [-921.363µs; -898.037µs] or [-74.097%; -72.221%]

scenario:TraceFlushBench/benchFlushTrace-opcache

• 🟩 execution_time [-932.439µs; -911.861µs] or [-74.411%; -72.768%]

scenario:TraceSerializationBench/benchSerializeTrace

• 🟩 execution_time [-38.292µs; -28.808µs] or [-8.481%; -6.381%]

scenario:TraceSerializationBench/benchSerializeTrace-opcache

• 🟥 execution_time [+9.886µs; +16.014µs] or [+2.913%; +4.719%]