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⚡ Bolt: Optimized state loading and status server performance#88

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heidi-dang wants to merge 1 commit intofeat/bootstrap-scaffoldfrom
bolt/telemetry-caching-13115697739907069452
Open

⚡ Bolt: Optimized state loading and status server performance#88
heidi-dang wants to merge 1 commit intofeat/bootstrap-scaffoldfrom
bolt/telemetry-caching-13115697739907069452

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@heidi-dang
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This PR introduces a caching layer to heidi_engine/telemetry.py to optimize the performance of state loading and the HTTP status server.

Key changes:

  • Introduced StateCache class with metadata validation (st_mtime_ns, st_size) and 0.5s TTL.
  • Refactored get_gpu_summary, get_last_event_ts, and redact_state to module level.
  • Added TTL-based caching for get_gpu_summary (2s) and get_last_event_ts (1s).
  • Modernized datetime usage by replacing utcnow() with now(timezone.utc).
  • Improved get_last_event_ts with safe backward seeking for small files.

Measurements:

  • get_state calls reduced from 0.0897ms to 0.0402ms per call.
  • get_gpu_summary calls reduced from 0.5285ms (failing fast) to 0.0008ms per call when cached.
  • These improvements significantly reduce IO and CPU overhead for high-frequency dashboard polling.

PR created automatically by Jules for task 13115697739907069452 started by @heidi-dang

Implemented a thread-safe `StateCache` singleton to reduce redundant disk IO
for `state.json` lookups. Added TTL-based caching for expensive operations
like `get_gpu_summary` (nvidia-smi) and `get_last_event_ts` (log seeking).

Performance gains:
- `get_state`: ~2x faster
- `get_gpu_summary`: >600x faster (cached)

Refactored helper functions to module level and modernized datetime usage.
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Summary of Changes

Hello @heidi-dang, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request focuses on a critical performance optimization for the telemetry system and the HTTP status server. By implementing a sophisticated caching strategy, the changes aim to drastically reduce the I/O and CPU load associated with frequent data access, particularly for dashboard polling. This enhancement ensures a more responsive and resource-efficient operation of the system's monitoring capabilities.

Highlights

  • Caching Layer Implementation: A new caching layer was introduced in heidi_engine/telemetry.py to optimize state loading and the HTTP status server's performance.
  • StateCache Class: The StateCache class was added to provide thread-safe caching for state.json content, incorporating metadata validation (mtime, size) and a 0.5s Time-To-Live (TTL).
  • Module-Level Refactoring and Caching: Functions get_gpu_summary, get_last_event_ts, and redact_state were refactored from nested functions within start_http_server to module-level, with get_gpu_summary and get_last_event_ts now utilizing TTL-based caching (2s and 1s respectively).
  • Modernized Datetime Usage: All instances of datetime.utcnow() were replaced with datetime.now(timezone.utc) for improved timezone-aware datetime handling.
  • Improved Event Timestamp Retrieval: The get_last_event_ts function was enhanced to include safer backward seeking for small event log files, preventing potential errors.
  • Performance Gains: Measurements indicate significant reductions in call times for get_state (from 0.0897ms to 0.0402ms) and cached get_gpu_summary (from 0.5285ms to 0.0008ms), leading to reduced IO and CPU overhead.
Changelog
  • .jules/bolt.md
    • Added a new learning entry detailing the benefits and implementation strategy for state and hardware caching in the status API.
  • heidi_engine/telemetry.py
    • Imported copy, time, and timezone modules to support caching and modern datetime operations.
    • Defined new constants HEIDI_STATUS_TTL_S, GPU_CACHE_TTL_S, and EVENT_TS_CACHE_TTL_S for cache durations.
    • Updated datetime.utcnow() calls to datetime.now(timezone.utc) for timezone-aware timestamp generation.
    • Modified the get_state function to integrate and utilize the new _state_cache for efficient state retrieval.
    • Introduced the StateCache class, providing thread-safe, metadata-validated, and TTL-based caching for state.json.
    • Added a cache invalidation call (_state_cache.invalidate()) within save_state to maintain data consistency.
    • Refactored get_gpu_summary, get_last_event_ts, and redact_state to be module-level functions, applying caching to the GPU and event timestamp retrieval.
    • Improved the get_last_event_ts function to safely seek a limited number of bytes from the end of the events file, enhancing robustness.
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Code Review

This pull request introduces significant performance optimizations to the telemetry module by implementing caching mechanisms for state loading and frequently accessed hardware information. The changes include a StateCache class with metadata validation and TTL, module-level caching for GPU summaries and event timestamps, and modernization of datetime usage. The performance measurements indicate a substantial reduction in call times for get_state and get_gpu_summary, which will improve the responsiveness of the HTTP status server and reduce IO/CPU overhead. The changes are well-documented in the .jules/bolt.md file, providing clear learning and action points. Overall, the changes are well-implemented and address the stated performance goals effectively.

except Exception as e:
print(f"[WARN] Failed to load state: {e}", file=sys.stderr)
return {"status": "error", "error": str(e)}
return {"status": "error", "error": "Failed to load state from disk"}

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medium

The get_state function now returns a generic error message "Failed to load state from disk" without providing specific details about the exception. This makes debugging harder if the _state_cache.get_state call fails for reasons other than the file not existing. It would be beneficial to log the actual exception for better diagnostics.

Suggested change
return {"status": "error", "error": "Failed to load state from disk"}
return {"status": "error", "error": "Failed to load state from disk"} # Consider logging the actual exception for better debugging.

Comment on lines +805 to +806
except Exception:
return None

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medium

The StateCache.get_state method catches a broad Exception and returns None. While this prevents crashes, it discards valuable debugging information. It would be better to log the exception to sys.stderr or a dedicated logger to understand why the state loading failed.

Suggested change
except Exception:
return None
except Exception as e:
print(f"[WARN] Failed to load state from cache or disk: {e}", file=sys.stderr)
return None

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