Graceful shutdown on SIGTERM caused by manual app stop

[lmagyar]

Proposed Changes

This is to prevent showing "Error" app status after plain manual app stop.

Finish scripts in pending PRs #667 #680 are also modified.

Related Issues

Summary by CodeRabbit

• Bug Fixes
  • Improved service termination and exit code handling across multiple background services to ensure proper shutdown behavior under specific conditions.

[coderabbitai]

Walkthrough

Five S6 finish scripts (nginx, share-homeassistant, taildrop, tailscaled, web) each receive an identical one-line change: the inner condition inside the exit_code_service == 256 branch now additionally requires exit_code_signal != 15 before writing the computed 128 + exit_code_signal halt exit code.

Changes

Signal 15 guard in S6 finish scripts

Layer / File(s)	Summary
Add exit_code_signal != 15 guard to exit_code_service == 256 branch tailscale/rootfs/etc/s6-overlay/s6-rc.d/nginx/finish, tailscale/rootfs/etc/s6-overlay/s6-rc.d/share-homeassistant/finish, tailscale/rootfs/etc/s6-overlay/s6-rc.d/taildrop/finish, tailscale/rootfs/etc/s6-overlay/s6-rc.d/tailscaled/finish, tailscale/rootfs/etc/s6-overlay/s6-rc.d/web/finish	All five finish scripts tighten line 18: the exit_code_service == 256 path now writes the computed halt exit code only when exit_code_signal != 15 in addition to exit_code_container == 0. Previously the signal value was not checked.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐇 A signal of fifteen means "please stop, be nice,"
No need to cry wolf or exit code splice.
Five scripts now agree: if SIGTERM's the call,
We quietly finish and don't fuss at all.
Hop hop, clean shutdown — no panic, no strife! 🌿

🚥 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 accurately describes the main change across all modified files: adding signal-based conditions to graceful shutdown handling for SIGTERM signals in finish scripts.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tailscale/rootfs/etc/s6-overlay/s6-rc.d/nginx/finish`:
- Line 18: Three finish scripts are missing the SIGTERM guard (`-ne 15`) that
prevents writing signal-based exit codes when services are manually stopped. In
the protect-subnets/finish, magicdns-egress-proxy/finish, and
magicdns-ingress-proxy/finish scripts, locate the condition that checks
`exit_code_container` and update it to include the `exit_code_signal -ne 15`
check alongside the existing `exit_code_container -eq 0` check, matching the
pattern already correctly implemented in nginx/finish and other scripts. This
ensures all services consistently skip writing exit codes on SIGTERM signals.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 5c0d145b-8535-4e9c-b700-ea5dcce850e9

📥 Commits

Reviewing files that changed from the base of the PR and between 6f8b8c5 and fbc7285.

📒 Files selected for processing (5)

• tailscale/rootfs/etc/s6-overlay/s6-rc.d/nginx/finish
• tailscale/rootfs/etc/s6-overlay/s6-rc.d/share-homeassistant/finish
• tailscale/rootfs/etc/s6-overlay/s6-rc.d/taildrop/finish
• tailscale/rootfs/etc/s6-overlay/s6-rc.d/tailscaled/finish
• tailscale/rootfs/etc/s6-overlay/s6-rc.d/web/finish