[WIP] perf: serialize telemetry batches on shared thread pool

[jpnurmi]

Warning

WIP    🚧🔨⏳⛔

• Introduce a thread pool that runs tasks in parallel and invokes completion callbacks in submission order.
• Add an internal telemetry module for coordinating logs and metrics startup, shutdown, and flush.
• Let the telemetry module own a shared serialization pool for enabled telemetry batchers.
• Use the pool for log and metric batch serialization while keeping completion ordered through the batcher.

before-vs-after.ftrace.zip

Close: #1862

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Codecov Report

❌ Patch coverage is 79.54545% with 90 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.04%. Comparing base (ff2f6a7) to head (ba24ac6).

Additional details and impacted files

@@                       Coverage Diff                        @@
##           jpnurmi/ref/sentry-telemetry    #1883      +/-   ##
================================================================
+ Coverage                         69.80%   76.04%   +6.23%     
================================================================
  Files                                94       94              
  Lines                             22133    22545     +412     
  Branches                           3930     4018      +88     
================================================================
+ Hits                              15451    17144    +1693     
+ Misses                             4719     4515     -204     
+ Partials                           1963      886    -1077     

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Spinlock held across heavy dump work

Medium Severity

batch_task_dump_pending runs batch_func and sentry__run_write_envelope while dump_pending_all still holds task_lock. Pool workers use a plain sentry__spin_lock to publish READY, so they busy-spin for the whole serialization and disk write. That stretches crash-flush latency and makes the RUNNING-wait timeout much easier to hit.

Additional Locations (1)

• src/sentry_batcher.c#L254-L274

 

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