[Part 4/6] feat(telemetry): add memory monitor with activity-aware recording and tests

[eLyiN]

Summary

Adds comprehensive MemoryMonitor that provides activity-aware memory tracking, automatic lifecycle management, and integration APIs for global monitoring. Uses components from Parts 1-3 for intelligent recording strategies.

Dependencies

⚠️ This PR depends on:

• [Part 1/6] feat(telemetry): add rate limiter and high-water mark tracker with tests #8110 - Part 1: Telemetry Primitives (RateLimiter, HighWaterMarkTracker)
• [Part 2/6] feat(telemetry): add activity detector with user interaction tracking #8111 - Part 2: Activity Detection (ActivityDetector, isUserActive)
• [Part 3/6] feat(telemetry): enhance metrics with performance monitoring APIs #8113 - Part 3: Metrics Enhancement (performance metrics, recording functions)

Review Order: Please review Parts 1-3 first (#8110, #8111, #8113), then this PR.

Related PRs - Enhanced Performance Monitoring Split

This is Part 4 of 6 in the split implementation of #2127:

• ✅ Part 1/6: [Part 1/6] feat(telemetry): add rate limiter and high-water mark tracker with tests #8110 (telemetry-primitives) - Foundation
• ✅ Part 2/6: [Part 2/6] feat(telemetry): add activity detector with user interaction tracking #8111 (activity-detector) - Activity tracking
• ✅ Part 3/6: [Part 3/6] feat(telemetry): enhance metrics with performance monitoring APIs #8113 (metrics-enhancements) - Performance metrics
• ✅ Part 4/6: [Part 4/6] feat(telemetry): add memory monitor with activity-aware recording and tests #8122 (memory-monitor) - YOU ARE HERE
• ⏳ Part 5/6: [Part 5/6] feat(telemetry): add activity monitor with event-driven snapshots #8124 (activity-monitor) - depends on Parts 1-4
• ⏳ Part 6/6: [Part 6/6] feat(cli): add activity monitoring hooks and integrate telemetry documentation #8125 (cli-integration) - depends on Parts 1-5
• 📋 Tracking Issue: [Split PRs] Enhanced Performance Monitoring Implementation - Split into 6 reviewable PRs #8120

Changes in This PR

MemoryMonitor (packages/core/src/telemetry/memory-monitor.ts)

Complete memory monitoring solution with activity-aware recording, high-water mark tracking, rate limiting with priority bypass, and comprehensive metrics including heap used, heap total, RSS, and external memory.

Memory Snapshot Types

ProcessMetrics and MemorySnapshot interfaces providing structured memory data with component attribution and activity state context.

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[eLyiN]

@jacob314 @joshualitt PR 4 Ready for Review

[eLyiN]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a comprehensive MemoryMonitor for telemetry, featuring activity-aware recording, high-water mark tracking, and rate limiting. The implementation is well-structured and includes a thorough test suite. My review focuses on improving the testability of the singleton pattern and the robustness and clarity of the tests to ensure long-term maintainability.

[joshualitt]

Thanks for the PR! Thoughts on periodically calling the cleanup() methods on HighWaterMarkTracker and RateLimiter perhaps on a much longer interval than the monitoring itself? While not strictly necessary with the current static keys, it should hopefully be a small change with minimal performance impact, and would proactively safeguard against potential future memory leaks if dynamic keys are ever introduced.

[eLyiN]

Thanks for the PR! Thoughts on periodically calling the cleanup() methods on HighWaterMarkTracker and RateLimiter perhaps on a much longer interval than the monitoring itself? While not strictly necessary with the current static keys, it should hopefully be a small change with minimal performance impact, and would proactively safeguard against potential future memory leaks if dynamic keys are ever introduced.

Great call on proactively cleaning up the tracker state. I've improved it, the latest commit now schedules periodic pruning of both the high-water mark tracker and the rate limiter, so even if we start emitting dynamic keys we won’t leak memory. While we were in there, we finished aligning the memory monitor with PR #10215 schema update, so the new metric attributes flow end-to-end. Tests are still all green.

[jacob314]