Differential D20547

[alp-dex] Drop queued settles older than 20s
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Authored by bytesofman on Sep 3 2026, 09:13.

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Fabien

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Fabien

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rABCc07f58c818a4: [alp-dex] Drop queued settles older than 20s

Summary

If we have very high volume, or bad server performance, it's possible a customer's order will take a long time to process. For a Cashtab user, we don't want them to see a spinner for 30s, leave the app or forget about the order (or try to make a new one), and then seemingly at random have the first one clear.

Arbitrarily refuse to process orders more than 20 seconds old. Cashtab can be set to timeout at this value, so the user can know that their order will in fact not go through from the UI directly. We can tweak this value depending on observed performance.

Reject POST /api/v1/swap with HTTP 408 if the request is at least
20s old when the settle queue job starts or immediately before broadcast.
Cashtab will abort at the same window; filling after that can double-pay
on retry. 408 is not ValidationError so Telegram does not treat this as an
invalid swap.

Test Plan

cd apps/alp-dex && npm test
Confirm assertSettleRequestFresh unit tests and the two 408 E2E cases (stale at queue start; stale after fuel, before broadcast)

Diff Detail

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rABC Bitcoin ABC

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Event Timeline

bytesofman created this revision.Sep 3 2026, 09:13

bytesofman held this revision as a draft.

Build Bitcoin ABC Diffs / Diff Testing (ai-review) passed.
CodeRabbit Review

Diff : committed changes only
Compare : HEAD → master
Directory : work
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Review complete
No findings ✔

7 files reviewed:

apps/alp-dex/SPEC.md
apps/alp-dex/src/app.ts
apps/alp-dex/src/constants.ts
apps/alp-dex/src/methods/settleAge.ts
apps/alp-dex/src/routes/settle.ts
apps/alp-dex/test/settle.test.ts
apps/alp-dex/test/settleAge.test.ts

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Harbormaster completed remote builds in B38012: Diff 61120.Sep 3 2026, 09:16

bytesofman published this revision for review.Sep 3 2026, 09:59

bytesofman edited the summary of this revision. (Show Details)

Fabien requested changes to this revision.Sep 3 2026, 13:47

Fabien subscribed.

Fabien added inline comments.

apps/alp-dex/src/constants.ts
28–36 ↗	(On Diff #61120)
apps/alp-dex/src/routes/settle.ts
67 ↗	(On Diff #61120)	Better store the creation timestamp, and use whatever function to set the value. That's a much better API than using a callback function to set the time

This revision now requires changes to proceed.Sep 3 2026, 13:47

Address review: drop Cashtab-specific JSDoc on SETTLE_MAX_QUEUE_AGE_MS; replace nowMs clock callback with a stored createdAtMs timestamp.

Build Bitcoin ABC Diffs / Diff Testing (ai-review) passed.
CodeRabbit Review

Diff : committed changes only
Compare : HEAD → master
Directory : work
────────────────────────────────────────

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major [Functional Correctness]
→ ]8;;vscode://file//work/apps/alp-dex/src/methods/settleAge.ts:32apps/alp-dex/src/methods/settleAge.ts:32]8;;

Reject timestamps that move backward.

Line 32 treats a negative age as fresh. If Date.now() moves backward
after receipt, an expired request can pass both checks and broadcast after
the 20-second limit. Reject `nowMs
Proposed fix

-    if (nowMs - receivedAtMs >= maxAgeMs) {
+    if (nowMs < receivedAtMs || nowMs - receivedAtMs >= maxAgeMs) {

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Review complete
1 finding ✔

Major 1

7 files reviewed: