Backend: add a graceful-shutdown drain test asserting in-flight exports complete before process exit

[Baskarayelu]

📋 Description

Shutdown ordering lives in shutdown.ts and is wired from bootstrap.ts. Exports run as longer-lived jobs via exportService.ts. There is no test proving that on SIGTERM the shutdown sequence waits for in-flight export jobs to finish (or checkpoint) before closing the DB and exiting.

Why this matters: killing the process mid-export corrupts or loses the artifact. A drain test pins the contract that shutdown waits for in-flight work, preventing a regression that reorders teardown.

🎯 Requirements & Context

• Add a jest suite that starts a simulated in-flight export, triggers the shutdown sequence, and asserts the export completes (or checkpoints) before the DB-close step runs.
• Assert new requests are rejected once draining begins.
• Assert a bounded drain timeout forces teardown if a job hangs (no infinite wait).
• Use fake timers for the timeout path.

Context & constraints

• TypeScript, jest. Mock the export job's completion signal; do not perform real file I/O.

🛠️ Suggested Execution

git checkout -b test/shutdown-export-drain
npm --prefix backend test -- shutdown

• Edge cases: no in-flight jobs (immediate teardown); job finishes just before timeout; job exceeds timeout (forced); multiple concurrent exports.

Example commit message

test(backend): assert shutdown drains in-flight exports before DB close

Pins the teardown ordering and the bounded drain-timeout fallback.

✅ Acceptance Criteria & Guidelines

Requirement	Target
Drain-before-close asserted	Required
Bounded timeout fallback covered	Required
Coverage of shutdown sequence	≥ 95%
jest + lint clean	Required
Timeframe	96 hours from assignment

💬 Community & Support

Join Discord: https://discord.gg/VpngvTjWa — comment to claim. 🚀

[YfengJ]

Hi maintainers, I would like to apply for this issue if it is available. If assigned, I will keep the scope focused on a graceful-shutdown drain test for in-flight exports, without changing unrelated shutdown/export behavior.