aa8028f96e
Wave 1 of the remediation plan for the 2026-09-03 feature test run. Two kiosks, one shape of defect, one critical consequence. Both kiosks read the state, decided in Python, and then wrote. Nothing stops two requests interleaving between the read and the write, so both see the same pre-state and both proceed. Reproduced on MySQL 5.6 over HTTP, five concurrent takes of 5 from a bin holding 5: all five were accepted and quantityonhand landed on -20, because each request wrote its own arithmetic. The ledger had recorded every one of them, so the cached quantity and the ledger disagreed permanently, which is the number the shop floor actually reads. The USB kiosk had the same shape: concurrent scans of one drive all succeeded and inserted several open custody rows, so one drive was recorded out to two people and the documented 409 never fired. The comparison now lives in the WHERE clause, where the database settles it at write time. printedparts._move_quantity issues UPDATE ... WHERE quantityonhand >= :n and treats rowcount 0 as the refusal, raising InsufficientStock, which take and adjust turn back into the message they already gave - carrying the quantity the database holds now, not the stale one the request read. The low-stock alert derives its before-value from what the write produced for the same reason. Both USB paths claim the device with ischeckedout (self-hosted) or status (external cmmc_usb) in the WHERE clause; the external one claims BEFORE writing the log line, so a refused claim leaves nothing to undo. Check-in is guarded the same way. After the fix, the same five concurrent takes: one accepted, four refused, quantityonhand 0 and the ledger sum 0. Check-in also closes EVERY open row for the device rather than the newest. One device can only be out once, so a second open row is corruption, and closing only the newest left the older ones open forever - the device then read as returned while its custody history said otherwise. Separately, usbcheckouts now records who handed a drive back (checkinsso/checkinname, migration usb0004checkinidentity). Returning for a colleague is a supported flow that the kiosk asks to confirm, but the row it wrote attributed the check-in to the HOLDER, so the custody history and the audit report both named somebody who was not there. Nullable and deliberately not backfilled: copying the holder's badge into old rows would manufacture evidence for the exact claim this stops making. Four tests. Both guards verified by planting: strip the condition out of either UPDATE and its test fails. Scope: product
USB plugin - CMMC USB check-in/out database contract
The USB plugin tracks removable-media check-in/out for CMMC compliance. Device
and log state live in a separate, read-write MySQL database (cmmc_usb),
reached with parameterized pymysql via cmmc_usb_connection(). Names of people
are resolved from the HR employee directory (see the employees plugin).
The plugin's own reference tables (usbdevicetypes, usbdevices,
usbcheckouts) live in the main app database; only the live check-in/out data
is in cmmc_usb.
The schema is standardized across sites - the
cmmc_usbcheck-in/out solution is the same deployment everywhere, so the tables below match as-is and no schema adaptation is needed. The database name may differ per site, though - setcmmc_usb_db_name(defaultcmmc_usb) to match the local name. The view recipe at the end is only a fallback for a site that somehow differs. (Contrast the employee directory, which genuinely varies per site.)
Connection
Credentials resolve settings-first, then environment, except the password which is env-only (never stored in the app database).
| Field | Setting key (editable in the setup wizard) | Env var (fallback) |
|---|---|---|
| Host | cmmc_usb_db_host |
CMMC_USB_DB_HOST |
| Database | cmmc_usb_db_name |
CMMC_USB_DB_NAME |
| User | cmmc_usb_db_user |
CMMC_USB_DB_USER |
| Password | (not stored) | CMMC_USB_DB_PASSWORD |
Set the password in .env; the setup wizard's Features step shows the exact
line to paste. This database is read-write - the app account needs
SELECT, INSERT, UPDATE. Engine is MySQL/MariaDB (pymysql).
Required schema
The plugin runs raw SQL against these tables (or views - see below).
devices
| Column | Type | Notes |
|---|---|---|
device_id |
VARCHAR | Primary key; the device serial/tag |
device_desc |
VARCHAR | Description |
device_owner |
VARCHAR | Owner |
status |
VARCHAR | Check-in/out state |
locker_location |
VARCHAR | Where the device is stored |
Operations: SELECT (list + by id), INSERT (register device), UPDATE
(edit fields, change status).
checkinoutlog
| Column | Type | Notes |
|---|---|---|
log_id |
INT (PK) | Auto id |
badge_number |
VARCHAR | Person's badge |
device_id |
VARCHAR | FK to devices.device_id |
action |
VARCHAR | check-in / check-out |
timestamp |
DATETIME | When it happened |
scanned_viruses |
(text/int) | Scan result |
locker_location |
VARCHAR | Locker at time of event |
sanitized |
(bool/int) | Sanitization flag |
Operations: SELECT (history per device), INSERT (log an event).
users
| Column | Type | Notes |
|---|---|---|
badge_number |
VARCHAR | Primary key; the scanned badge |
first_name |
VARCHAR | Given name |
last_name |
VARCHAR | Surname |
Operations: SELECT by badge, INSERT (auto-add a badge on first scan).
Employee directory dependency
To turn a scanned badge into a name, the plugin also reads the HR employees
directory (via the employees plugin's connection). A badge shaped 0<digits>BZ
carries a PayNo (the digits); lookups try employees.SSO and employees.PayNo.
See plugins/employees/README.md for that schema and connection.
Adapting a different site schema (recommended: views)
Sites whose USB-tracking database uses different table/column names should
create read-only/updatable views named devices, checkinoutlog, and
users that map local columns to the names above. Example:
CREATE VIEW devices AS
SELECT
asset_tag AS device_id,
description AS device_desc,
owner AS device_owner,
state AS status,
storage_bay AS locker_location
FROM usb_assets;
Because the plugin writes to devices/checkinoutlog/users, either make the
views updatable (single-table views usually are) or expose real tables with
these column names. Grant the app account SELECT, INSERT, UPDATE.
Notes:
device_idandbadge_numberare the natural keys the plugin matches on.- If
cmmc_usbis unreachable, USB endpoints return an error and the rest of the app keeps working (the feature degrades, it does not crash the app).