Hang Capture Service

[naftaly]

This PR creates a service to capture hangs. Hangs are sent in the same manner as they are on Android as described here. A similar span is also sent using iOS terminology as an interim in order for it to appear in the timeline.

• Currently stack traces are not sent, this is for a future PR.
• The iOS span appears as "emb_thread_blockage" in the Performance timeline.
• Limit is set to 200 hangs per session. Currently hard coded.
• Limit is set to 0 samples per hang. Currently hard coded.
• Add a session attribute named emb-thread-blockage with the count of hangs in the session.
• Currently using ux for the type, I think it needs to be perf.thread_blockage.

Client Work

• Add limits.
• Figure out what spans to log (ANR or Hang), and get backend work done accordingly.
• If there's an un-terminated hang span on startup, we should determine that a crash occurred due to a watchdog event (SIGKILL 0x8badf00d), but still close the span and have it appear in the timeline.
• Understand the overflow error that is currently commented out.

Backend work

• Make sure the correct naming is used on each platform. (iOS => Hang)
• Show perf.thread_blockage spans in timeline.
• Add remote config limits, here's the structure used in the app:

hang_limits: {
    hang_per_session: Uint,
    samples_per_hang: Uint
}

Gate

Set hang_per_session = 0 to ensure the watchdog doesn't run.

Visuals

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[github-actions]

	Warnings
⚠️	No CHANGELOG entry added.

Generated by 🚫 Danger Swift against 2225322

[codecov]

Codecov Report

❌ Patch coverage is 74.82877% with 147 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.10%. Comparing base (5ea59ef) to head (4b7fccc).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../EmbraceCore/Capture/Hang/HangCaptureService.swift	7.27%	102 Missing ⚠️
...onfigurable/RemoteConfig/RemoteConfigPayload.swift	36.00%	16 Missing ⚠️
...ceCore/Capture/Hang/Watchdog/NanosecondClock.swift	65.51%	10 Missing ⚠️
...braceCore/Capture/Hang/Watchdog/HangWatchdog.swift	95.55%	8 Missing ⚠️
...ts/TestSupport/Mocks/MockEmbraceConfigurable.swift	28.57%	5 Missing ⚠️
Sources/EmbraceConfiguration/HangLimits.swift	42.85%	4 Missing ⚠️
Sources/EmbraceCore/Capture/CaptureServices.swift	96.87%	1 Missing ⚠️
...reTests/Capture/Hang/HangCaptureServiceTests.swift	99.34%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
- Coverage   89.44%   89.10%   -0.34%     
==========================================
  Files         465      470       +5     
  Lines       29366    29936     +570     
==========================================
+ Hits        26265    26675     +410     
- Misses       3101     3261     +160     

Files with missing lines	Coverage Δ
Sources/EmbraceCaptureService/CaptureService.swift	90.38% <100.00%> (+1.25%)	⬆️
...urces/EmbraceCommonInternal/Locks/UnfairLock.swift	100.00% <ø> (ø)
...figInternal/EmbraceConfigurable/RemoteConfig.swift	79.43% <100.00%> (-5.86%)	⬇️
...figuration/EmbraceConfigurable/DefaultConfig.swift	91.30% <100.00%> (+0.39%)	⬆️
...braceCore/Capture/UX/View/ViewCaptureService.swift	65.59% <100.00%> (-1.22%)	⬇️
...rces/EmbraceCoreDataInternal/CoreDataWrapper.swift	77.77% <ø> (-0.13%)	⬇️
...ces/EmbraceIO/Capture/CaptureService+Helpers.swift	100.00% <100.00%> (ø)
...rces/EmbraceIO/Capture/CaptureServiceBuilder.swift	100.00% <100.00%> (ø)
...ests/Capture/UX/View/ViewCaptureServiceTests.swift	100.00% <100.00%> (ø)
...s/EmbraceCoreTests/Public/Embrace+SetupTests.swift	85.71% <ø> (ø)
... and 10 more

... and 3 files with indirect coverage changes

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[Copilot]

Pull Request Overview

This PR implements a hang capture service to detect and report app hangs on iOS. The service monitors the main RunLoop and generates OpenTelemetry spans when hangs exceed Apple's default 0.25 second threshold.

Key changes include:

• Creates a HangWatchdog that monitors the main RunLoop using CFRunLoopObserver to detect when the thread is blocked
• Implements HangCaptureService that converts hang events into OpenTelemetry spans with "emb-thread-blockage" naming
• Adds configuration support with HangLimits to control the number of hangs per session (200) and samples per hang (0)

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
Tests/TestSupport/Mocks/MockEmbraceConfigurable.swift	Adds hangLimits property to mock configuration
Tests/TestSupport/EditableConfig.swift	Adds hangLimits property to test configuration
Tests/EmbraceIOTests/CaptureServiceBuilderTests.swift	Updates tests to include HangCaptureService in service count validation
Tests/EmbraceCoreTests/Capture/Hang/HangCaptureServiceTests.swift	Comprehensive test suite for hang detection functionality
Sources/EmbraceIO/Capture/CaptureServiceBuilder.swift	Integrates hang watchdog into default capture services
Sources/EmbraceIO/Capture/CaptureService+Helpers.swift	Adds helper method to create HangCaptureService
Sources/EmbraceCore/Capture/Hang/Watchdog/NanosecondClock.swift	High-precision timing utility for hang measurement
Sources/EmbraceCore/Capture/Hang/Watchdog/HangWatchdog.swift	Core hang detection implementation using RunLoop observers
Sources/EmbraceCore/Capture/Hang/HangCaptureService.swift	Service that converts hang events to OpenTelemetry spans
Sources/EmbraceCore/Capture/CaptureServices.swift	Integrates hang limits configuration and session lifecycle
Sources/EmbraceConfiguration/HangLimits.swift	Configuration class for hang capture limits
Sources/EmbraceConfiguration/EmbraceConfigurable/DefaultConfig.swift	Adds hangLimits to default configuration
Sources/EmbraceConfiguration/EmbraceConfigurable.swift	Adds hangLimits property to configuration protocol
Sources/EmbraceConfigInternal/EmbraceConfigurable/RemoteConfig/RemoteConfigPayload.swift	Remote configuration support for hang limits
Sources/EmbraceConfigInternal/EmbraceConfigurable/RemoteConfig.swift	Implements hangLimits property for remote config
Sources/EmbraceCommonInternal/Locks/UnfairLock.swift	Minor extension reorganization
Sources/EmbraceCaptureService/CaptureService.swift	Adds session lifecycle methods to base CaptureService

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[github-actions]

🚀 Swift Test Performance Report

✅ Performance Improvement

Branch	Average Duration	Standard Deviation	Sample Size
PR Branch	1.553s	±1.418672s	20 runs
Main Branch	1.994s	±1.568736s	20 runs

Performance Impact

• Absolute Difference: -.441s
• Relative Change: -22.00%
• T-statistic: -.932

📊 Difference not statistically significant

Analysis

🎉 Significant improvement detected - Great optimization work!

📊 View detailed statistics

• Test Configuration: 20 runs per branch with 3 warmup runs
• Runner: macOS Latest (parallel execution)
• Swift Version: Latest available
• Statistical Test: Two-sample t-test approximation
• Workflow: Swift Test Performance Comparison
• Run ID: 17414136709

Note: This test uses a reduced sample size (20 runs) for faster CI execution.
For production performance validation, consider running with larger sample sizes.

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This comment will be updated on subsequent commits.