Fix WebSocket slot leak: shut down read half on idle close so the epoll worker reclaims the connection

[wksantiago]

Closes #128

Summary by CodeRabbit

• Bug Fixes
  • Improved WebSocket shutdown handling by preventing close logic from running on connections that are already closed.
  • Updated the shutdown approach to signal EOF to the background worker so cleanup happens through the normal path, reducing the chance of connections lingering after disconnect.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 09243daf-ed24-41bf-b82e-7c9c4835c5dd

📥 Commits

Reviewing files that changed from the base of the PR and between a610a7f and 8d0a1a9.

📒 Files selected for processing (1)

• src/connection.zig

🚧 Files skipped from review as they are similar to previous changes (1)

• src/connection.zig

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Walkthrough

Connection.closeWs now returns early for already-closed websocket connections, and otherwise shuts down only the socket read half with shutdown(..., SHUT.RD) instead of closing the fd off-thread. This keeps the fd visible to epoll so the worker observes EOF and performs its normal cleanup path.

Changes

WebSocket shutdown fix

Layer / File(s)	Summary
closeWs: replace close with shutdown(SHUT.RD) src/connection.zig	Connection.closeWs now skips already-closed websockets, then calls shutdown(..., SHUT.RD) on the socket fd so the worker can observe EOF and run its cleanup path.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~5 minutes

Poem

🐇 A socket once shut with a snap,
Left cleanup way off of the map.
Now EOF hums,
The worker then comes—
And frees up the slot in a lap!

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main fix: using read-half shutdown so the epoll worker reclaims leaked WebSocket slots.
Linked Issues check	✅ Passed	The change matches issue #128 by replacing off-thread close with shutdown(.recv) so the worker observes EOF and runs cleanup.
Out of Scope Changes check	✅ Passed	The only extra guard against already-closed sockets is tightly related to the WebSocket close path and not out of scope.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/ws-slot-leak-idle-close

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