Files
shopdb-flask/docs/adr/ADR-004-deployment-topology.md
cproudlock f9d6b57f0f Move the documentation to the line that ships, and correct it against the code
The docs lived on one lineage and the fleet code on another. That is why six
pages described a shared fleet key as how an agent authenticates, why
COLLECTOR-AUTH had to warn that the per-PC credential code was not in the
repository it sat in, and why ADR-019 recorded a decision whose implementation
was somewhere else. Documentation that cannot see the code it documents goes
stale by construction, and no amount of editing fixes that.

So the corpus moves here: 84 files, 56 pages, 20 ADRs, the proposals, INDEX.md,
llms.txt and both gates. Filenames are unchanged, because a wiki page name is
derived from the filename and a rename breaks every link anybody saved.

THE POINT OF THE MOVE IS THE CORRECTION IT ENABLES. Every caveat that said "not
in this tree" was false the moment the files landed beside the code, so each was
rewritten from what is actually here:

- COLLECTOR-AUTH gained the real enroll request body, the two bounds on the
  unauthenticated route (per-IP rate limit, pending cap with stale rows dropped
  before a real PC is refused), and the rejected pending reason that binds to
  the endpoint identity rather than the nonce.
- ADR-019 now describes an implementation that is present, including its tests,
  and says plainly that what remains is the FLEET migration, not the code.
- proposals/device-identity claimed phase 1 was unbuilt. plugins/computers
  declares deviceid on the collector schema and prefers it over the older
  fallbacks. Corrected in the page, its summary and the index.

WINDOWS/IIS IS NOW DOCUMENTED AS THE LEGACY PATH, per the product decision, and
carefully: it is what production runs today. Every Windows page opens by saying
it is supported, not for a new site, and where a new site should go instead. No
procedure was cut - an operator on an IIS box at 2am needs these pages to work
exactly as well tomorrow. MIGRATE-TOPOLOGY stops being a footnote and becomes
the off-ramp, which is why it nearly doubled: what was there did not match how
the Docker stack really works here.

The Docker material that already lived on this line was kept and given
ownership rather than buried under the ported Windows-centric prose: DEPLOY now
describes the four services, the migrate service that runs the upgrade chain
before api starts, TLS terminated by nginx, and the plugin count corrected from
thirteen to seventeen - a number both lineages had wrong.

ROADMAP is rewritten from evidence rather than memory: what has shipped, read
out of the changelog, the ADRs and the manifests, and ahead of it exactly two
items - finalize a distributed release and polish the setup wizard.

PROJECT-MAP is generated and was stale; the GENERATOR was what was wrong.
--check passes now.

API-REFERENCE is retired to a pointer. /api/docs serves 573 operations with
derived auth, query parameters and harvested examples, and a hand-written page
competing with that is a liability. The file stays so its wiki page and its
inbound links survive.

AND THE MOVE TURNED ON A SCRUB THAT HAD NEVER RUN HERE. test_docs_publishable
keys on docs/*.md, which this line did not have, so it skipped - its own comment
predicted what would surface. Porting the corpus activated it and it found 48
lines that must not reach a published wiki: branch names abbreviating the site,
assistant-tooling paths, the site name in two deployment pages, and an employee
ID in a Windows path that the scrub does not even look for.
2026-09-19 09:10:15 -04:00

101 lines
5.4 KiB
Markdown

<!-- docmeta
purpose: explanation
audience: adopter
status: current
summary: Why every site runs its own instance instead of one multi-tenant deployment.
loadwith: none
-->
# ADR-004: Deployment topology (per-site instances)
- **Status:** ACCEPTED
- **Date:** 2026-05-08
- **Deciders:** ShopDB maintainers
## Context
shopdb-flask manages shop-floor inventory. If multiple GE Aerospace sites adopt it, the deployment can take one of two shapes:
| Model | How it works |
|---|---|
| **Per-site instances** | Each site runs its own Flask + MySQL + Vue stack. Each site has its own DB, its own users, its own enabled-plugin list, its own deploy. Sites are isolated. |
| **Multi-tenant single instance** | One central Flask + MySQL + Vue stack serves all sites. A `siteid` foreign key on every asset partitions data. Auth distinguishes which site a user belongs to. |
The codebase today is single-tenant per deployment. There is no `siteid` column, no tenant filter, no cross-site auth model. Plugins can be enabled / disabled but only globally for the running instance.
## Decision
**Per-site instances.** Each adopting site runs its own dedicated stack. The framework does not support multi-tenancy.
Each site:
- Owns its database (own credentials, own backup policy, own retention). The
database charset is part of the contract: it must be **utf8mb4**
(`utf8mb4_unicode_ci`). The migration chain creates every table utf8mb4, and
the connection pins `?charset=utf8mb4`. A site that creates the database with
a different default charset (older MySQL defaults to latin1) gets a schema
that silently diverges from every other site. See `docs/DEPLOY.md`.
- Picks its own enabled plugins
- Configures its own JWT secret, CORS allowlist, Zabbix integration, Active Directory binding
- Deploys at its own cadence
The framework provides:
- A `Dockerfile` and `docker-compose.yml` template suitable for a single-site deploy
- A `.env.example` listing all required environment variables
- A `docs/DEPLOY.md` walking through a fresh-site install
## Consequences
### Positive
- Simpler code: no tenant filter on every query, no cross-tenant auth, no shared-state partitioning bugs.
- Sites are independent. A schema change at one site does not affect another. A plugin crash at one site does not blast radius to other sites.
- Clear ownership: each site's IT team owns their own stack and data. Compliance and audit boundaries match operational boundaries.
- Aligns with how GE Aerospace sites already operate (independent IT, independent shop floors).
### Negative / cost
- No cross-site reporting out of the box. If GE corporate ever wants a fleet-wide view, it has to be built on top (e.g., a roll-up dashboard that queries each site's API). That layer is out of scope for the framework.
- Each site administers its own stack. Higher operational overhead than a single central instance, but each site already runs its own infrastructure.
- Updates require visiting each site's deploy. Fine for the current adoption model; revisit if dozens of sites adopt.
### Neutral
- No `siteid` column needed. The existence of one DB per site is the partition.
## Alternatives considered
1. **Multi-tenant single instance.** Lower operational overhead at scale, easier cross-site reporting, but adds significant code complexity and risk: every query needs a tenant filter, auth gets complex, schema migrations affect every site at once, and a bug at one site can leak data across sites. Rejected for v1; revisit if and only if more than five sites adopt and operational overhead becomes painful.
2. **Hybrid: per-site DB but central app server.** Adds the operational complexity of multi-tenancy without isolating the failure domain (one app crash = all sites down). Rejected.
## Migration strategy (resolved)
Deploys run two commands: `flask db upgrade` then `flask plugin upgrade-all`
(lean/ADR-014 sites add an optional `flask plugin prune-schema` at initial
provisioning). The core Alembic chain applied by `flask db upgrade` creates the
full core AND bundled-plugin schema through the chain head (this includes
migration `7c04_fold_plugin_schema`). But every bundled plugin still carries its
own Alembic chain per ADR-008: `flask plugin upgrade-all` stamps each plugin's
own chain (the `alembic_version_<plugin>` tables) and applies any plugin-specific
migrations added after the ownership cutover. The earlier Phase 7B state that
folded everything into core with no per-plugin chains was superseded by ADR-008's
per-plugin ownership. A fresh `flask db upgrade` reproduces the live core schema
exactly (verified on a scratch DB).
External (out-of-tree) plugins per ADR-003 ship their own migrations too; the
framework runs the same per-plugin chain mechanism (ADR-008) for both bundled and
external plugins.
## Open questions
- Should the framework provide an optional **read-only fleet roll-up** mode where a "central" instance can pull aggregate metrics from each site's API? Defer. Out of scope for v1.
- Backup strategy per site: framework recommendation, or each site decides? Framework should publish a recommended backup runbook (mysqldump + offsite copy) but not enforce.
- Auth federation: each site has its own user table, or sites can share an LDAP / SSO? Recommend documenting the LDAP config knob in `.env.example` so sites can plug in their own auth without code change.
## References
- `shopdb/config.py` (currently single-tenant, no `siteid`)
- ADR-001 (asset model is per-site, not cross-site)
- ADR-003 (plugin distribution per site)