fix: prevent race condition in objectstore auth sync

[shunkakinoki]

Problem

When the objectstore bootstraps, syncAuthFromBucket() uses os.RemoveAll() to wipe the local auth directory before pulling from S3. This triggers a race condition:

1. syncAuthFromBucket() wipes local auth directory with RemoveAll
2. File watcher detects deletions and propagates them to remote store
3. syncAuthFromBucket() then pulls from S3, but files are now gone

This causes auth files to be permanently deleted from S3 on every service restart.

Solution

Use incremental sync instead of delete-then-pull. Just ensure the directory exists and overwrite files as they're downloaded from S3. This prevents the watcher from seeing spurious delete events.

Testing

• Built and verified the fix locally
• Auth files now persist correctly across service restarts

[gemini-code-assist]

Summary of Changes

Hello @shunkakinoki, 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 resolves a critical race condition within the object store's authentication synchronization process. Previously, a full directory wipe during bootstrap could lead to the unintended deletion of authentication files from R2 storage due to interaction with file watchers. The change implements an incremental synchronization approach, ensuring data integrity and preventing permanent loss of authentication data upon service restarts.

Highlights

• Race Condition Fix: Addressed a critical race condition during object store bootstrapping where the os.RemoveAll operation inadvertently triggered file watcher events, leading to the deletion of authentication files from R2 storage.
• Incremental Synchronization: Modified the syncAuthFromBucket function to perform an incremental synchronization. Instead of wiping the entire local authentication directory, the function now ensures the directory exists and overwrites files as they are downloaded, preventing spurious delete events.

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[gemini-code-assist]

Code Review

This pull request correctly identifies and fixes a critical race condition that could lead to data loss in the object store. The change to an incremental sync in syncAuthFromBucket is a good approach to prevent the file watcher from erroneously deleting remote auth files. However, this fix introduces a new issue where stale local auth files are no longer cleaned up, which could pose a security risk. I've added a detailed comment with a suggestion on how to address this to make the sync process more robust.

[Copilot]

Pull request overview

This PR fixes a critical race condition in the objectstore authentication synchronization that was causing permanent deletion of auth files from R2 on every service restart.

Key Changes:

• Removed os.RemoveAll() call that was wiping the local auth directory during sync
• Changed to incremental sync approach that overwrites files as they're downloaded from R2
• Updated error message from "recreate auth directory" to "create auth directory" for accuracy

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[shunkakinoki]

@luispater Would love for review 🙇‍♂️

[shunkakinoki]

@luispater Gently pinging the above 🙏