fix(turbopack-node): incorrect idle_workers stats

[xusd320]

This pull request refactors the worker creation and tracking logic in the Node.js pool, with a focus on simplifying how pending worker creations are managed and improving the robustness of worker statistics updates. The main changes are grouped into two themes: improvements to statistics handling and simplification of the worker creation queue.

Improvements to statistics handling:

• Replaced direct subtraction with saturating_sub in the NodeJsPoolStats methods to prevent underflow when decrementing counters such as booting_workers, workers, and queued_tasks. [1] [2]

Simplification of the worker creation queue:

• Refactored PENDING_CREATIONS to store only the oneshot::Sender<u32> instead of a tuple with WorkerOptions, reducing unnecessary data storage.
• Updated the logic in create_worker and worker_created to match the new structure of PENDING_CREATIONS, simplifying the push and pop operations and removing redundant code related to WorkerOptions. [1] [2]
• Added a conversion of WorkerOptions to napi_options early in create_worker for cleaner code and more explicit handling of options.

[gemini-code-assist]

Summary of Changes

Hello @xusd320, 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 refines the worker management system within turbopack-node by addressing two key areas: improving the reliability of worker pool statistics and simplifying the worker creation process. The changes prevent statistical underflow and streamline the internal handling of pending worker creations, resulting in a more robust and maintainable codebase.

Highlights

• Robust Statistics Handling: Replaced direct decrements with saturating_sub for worker and task counters in NodeJsPoolStats to prevent potential underflow issues and ensure accurate statistics.
• Simplified Worker Creation Queue: Streamlined the PENDING_CREATIONS queue to store only oneshot::Sender<u32>, removing redundant WorkerOptions storage and simplifying the logic for adding and retrieving pending worker creation requests.
• Cleaner Worker Creation Logic: Introduced an early conversion of WorkerOptions to napi_options in create_worker and simplified the worker_created function by removing unnecessary worker pool recording logic, focusing solely on sending the worker ID.

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[gemini-code-assist]

Code Review

This pull request effectively improves the robustness of worker statistics by using saturating_sub to prevent underflow errors, and it simplifies the worker creation logic by refactoring PENDING_CREATIONS. However, the simplification in worker_created introduces a potential resource leak. When a task waiting for a worker is cancelled, the newly created worker can become orphaned. I have provided a specific comment with a suggested fix to handle this scenario by terminating the orphaned worker.