Two scoped users, pos_terminal and pos_ingest, with an ACL that keeps a
till to its own topics: it can publish its bills, registrations and
heartbeats, read its own acks, and nothing else. It cannot reach
nearle/riders/# or doormile/#, and cannot forge an ack — only the ingest
writes those.
admin is deliberately left unrestricted. Its credentials are compiled
into the rider app, so narrowing it would cut off the live fleet without
warning; that change needs someone to confirm nothing else uses it
first. Because admin's entry grants everything, applying the ACL changed
nothing for existing traffic — verified by watching riders 852 and 1114
keep publishing battery, speed and periodic logs throughout.
The scoping was verified by publishing as pos_terminal to four topics
and observing which arrived: the order did, the rider topic, the
doormile topic and its own ack topic did not.
Config and password file were backed up first; the rollback is one cp
and a container restart.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A till holds every bill in its own SQLite database and keeps it for
seven days after we acknowledge it, marking one synced only when its id
comes back in an ack. Everything here follows from that.
Silence is not acceptance, so a failing ingest publishes nothing at all
and the terminal simply sends again. A duplicate is a success, because
at-least-once delivery means a lost ack legitimately re-delivers bills
we already hold, and calling those failures would strand a day of
takings on the till. Deduplication is a unique index on the terminal's
UUID plus an advisory lock held for the transaction.
Bills land in pos_orders / pos_order_items rather than orders: a counter
bill carries a cashier, a terminal, a rounding adjustment, promos,
loyalty movement and a payment split that orders has nowhere to put, and
forcing one into the other loses whatever does not fit. Stock is *not*
split — a counter sale writes the same productstocks rows an app order
does, through helpers extracted from createOrderTx so the rule that
prevents overselling has one implementation rather than two.
GetRevenueSummary and GetSalesSummary were extended to union the new
table in; any new report has to remember the same.
Terminal health goes to Redis under a 90-second TTL, sharing the
instance the express backend uses. A heartbeat is a fact with an expiry
date: a till that loses power stops refreshing and ages off the board by
itself, where a Postgres row would need ~288k writes a day and a reaper.
Proven end to end against the live estate before commit: a bill over
HTTP and one over the real Mosquitto broker, the same bill three times
producing one row and one stock movement, and a heartbeat arriving on
the health endpoint. All probe data was removed afterwards.
Four things that only surfaced against real data. An unset jsonb column
failed the very first bill. Product SKUs are unusable as barcodes — 6,245
products share 93 SKUs and "1" covers 5,794 of them — against the till's
unique index, so barcodes fall back to the product id. A taxpercent of
-1 exists and would have put negative GST in a filed slab. And a product
with id 0 exists, which can never be billed and is now skipped.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
