fix: fix file locking error when removing cache folder

[ChenZiHong-Gavin]

This PR addresses cache-related errors by improving resource management and making the temporary workspace cleanup process more robust.

[gemini-code-assist]

Summary of Changes

Hello @ChenZiHong-Gavin, 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 addresses cache-related errors by improving resource management and making the temporary workspace cleanup process more robust. It ensures that Engine instances are explicitly deallocated and that workspace directories can be reliably removed, even when encountering common file system access issues.

Highlights

• Resource Management: Implemented explicit garbage collection for the Engine object within the run_graphgen function, ensuring resources are properly released after execution, even in case of errors.
• Robust Workspace Cleanup: Enhanced the cleanup_workspace utility to handle potential permission issues during directory removal by introducing an error handler that attempts to set write permissions and retries the deletion.

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[gemini-code-assist]

Code Review

This pull request aims to fix a cache error by improving resource cleanup. In webui/app.py, it introduces manual garbage collection for the Engine object. In webui/utils/cache.py, it makes the workspace cleanup more robust by handling errors during file deletion.

My review focuses on making these fixes more robust.

• I've suggested explicitly terminating Ray actors in app.py to prevent resource leaks, as del and gc.collect() alone are not sufficient.
• In cache.py, I've pointed out that silently ignoring cleanup errors can hide persistent issues and suggested a safer way to modify file permissions to avoid unintended side effects.

Overall, the changes are in the right direction, but the suggested improvements will make the resource management more reliable.

[gemini-code-assist]

Silently swallowing exceptions with except Exception: pass can hide underlying issues and make debugging difficult. If the cleanup consistently fails for some reason, you would have no way of knowing, and temporary files could accumulate. Consider logging the exception here, even if you don't re-raise it, so that persistent problems can be identified.