tenant-engine/workplans/TEN-WP-0009-postgres-production-store.md

id	type	title	domain	repo	status	owner	topic_slug	created	updated	depends_on	unblocks	state_hub_workstream_id
TEN-WP-0009	workplan	PostgreSQL as the production store, SQLite for dev and test	infotech	tenant-engine	finished	claude	tenant-lifecycle	2026-08-16	2026-08-21	TEN-WP-0007	TEN-WP-0008	3bf3b4ab-a116-4914-b2d8-d3c430754956

TEN-WP-0009 - PostgreSQL production store

Move the production store from SQLite-on-a-PVC to the fleet's CloudNativePG infrastructure. SQLite stays, deliberately, as the dev and test backend.

Why this reverses an earlier decision

TEN-WP-0005-T02 chose SQLite over PostgreSQL on purpose, and the reasoning was sound at the time: TEN-WP-0004 had shipped SQLite on a PVC, so "adding an unused Postgres path would have been dead code". The TenantStore Protocol was kept precisely as the seam for this change.

Three things have changed since:

1. The PVC is now blocking work. The volume is ReadWriteOnce, which forces strategy: Recreate and makes a side-by-side canary impossible — the constraint TEN-WP-0008-T02 ran into when onboarding to staged promotion. The store choice is no longer invisible to anything outside this repo.
2. The infrastructure is already there and already proven. The CloudNativePG operator runs on railiance01 with seven clusters, and user-engine — our sibling service, sharing the tenant_id key — has run its own user-engine-pg for 19 days.
3. A Postgres path is no longer unused. It becomes the production path, so the dead-code objection no longer applies.

SQLite is not being removed. It stays as the dev and test backend, where a zero-setup file-backed store is genuinely the right tool, and it keeps the conformance suite honest by forcing the Protocol to stay a real seam rather than a formality wrapped around one implementation.

Credential handling

Corrected 2026-08-17. This section originally said CloudNativePG mints an X-app secret we reference with secretKeyRef, as user-engine does. That is true for a cluster's own app database — and wrong for the path we are actually taking.

railiance-platform/docs/rapp-postgres-boundary.md is explicit: rapp-postgres owns the role and database provisioning surface for the shared cluster, and "the workload receives a short-lived lease through the platform broker" — the OpenBao database secrets engine — rather than a static secret. railiance-platform retains cluster-wide governance and the credential-broker grant catalog.

Consequences, and the second one is real work:

• We do not provision our own database. We declare a consumer request and rapp-postgres provisions it. Writing a CNPG Database manifest into this repo's deploy/, or adding a managed role to a shared cluster's spec, would both be reaching across that boundary — the latter also mutating shared infrastructure other consumers depend on.
• Credentials are leased, not mounted. A short-lived lease means the connection string can change under a running pod, so the store cannot read a DSN once at startup and hold it forever. T03 and T05 must account for credential refresh; a long-lived pool built on an expired lease fails at the worst possible moment.

Either way no secret enters this repo, this workplan, or any evidence dump. Runtime secret custody stays OpenBao's per SCOPE.md, which is exactly what the broker lease implements.

Placement: shared by default, movable by design

Dedicated-vs-shared is not a decision this workplan should settle once, and tenant-engine is the wrong place to settle it for the platform. The estate has distinct elements — railiance, NetKingdom, HelixForge, Coulomb — plus tenants layered on top, and which repo belongs to which grouping is not yet organised. On top of that, isolation level is heading toward being a product property: plans will differ in how much isolation they buy.

So the requirement here is portability, not placement:

• start on a shared cluster, because it is cheaper on a single node and nothing yet justifies dedicated capacity;
• make moving to a dedicated cluster — or to a different shared one — an operational change, not a code change;
• never let the decision leak into the application.

What that demands of this repo, and all of it is cheap if done now and expensive to retrofit:

1. Connect by injected URL only. No cluster name, namespace, host, or database name anywhere in src/. The application must be unable to tell whether it is on a shared or dedicated cluster.
2. Own a whole database, not a set of tables in someone else's. Sharing a cluster is a capacity decision; sharing a database would entangle schemas and make relocation a merge rather than a move. A dedicated database inside a shared cluster relocates with a dump and a restore.
3. No cross-database joins or co-location assumptions, which the repo boundary already forbids — tenant_id is the only key shared with user-engine. Placement must not quietly become a dependency.
4. Idempotent schema creation, so a fresh target comes up correct without a hand-built database.

Then "move tenant-engine to dedicated" is: create the target cluster, dump, restore, swap the secretKeyRef, restart. No rebuild, no release, no code review.

What this repo does not own: the placement policy — which element or tenant gets dedicated capacity and when. That is a platform concern, and tenant-engine implementing its own would be the same boundary error as building a fleet drift-detector because we got bitten. Raised with railiance-platform separately; see T01.

T01 - Make placement portable and provision on shared capacity

id: TEN-WP-0009-T01
status: done
priority: high
state_hub_task_id: "b4701256-f235-4474-9dcf-7cb09f62b873"

Target: platform-pg, via a PostgresConsumer declaration to rapp-postgres. Not net-kingdom-pg or apps-pg, and not provisioned by us.

Reasoning, revised 2026-08-17 after finding the actual contract. The candidate list originally weighed product-family fit and would have picked net-kingdom-pg. But platform-pg is the shared cluster that has a governed provisioning path — rapp-postgres owns its consumer declarations, role provisioning, isolation tests, and recovery procedure. The other clusters carry their roles as hand-added entries in the shared cluster spec (net-kingdom-pg has privacyidea, apps-pg has vergabe and coulomb_social). Choosing product-family fit would mean improvising outside the one contract that exists, to gain an affinity that portability makes cheap to change later anyway. audit-core is the precedent: a platform service, on platform-pg, declared as a consumer.

Note the deviation from user-engine and why: they run a dedicated user-engine-pg. We are deliberately not copying that. Their choice is fine and ours is reversible; picking dedicated now would spend capacity on an isolation guarantee nothing has asked for yet.

The declaration to request, modelled on consumers/audit-core.yaml:

apiVersion: rapp-postgres.railiance.io/v1alpha1
kind: PostgresConsumer
metadata:
  name: tenant-engine
spec:
  database: tenant_engine
  schema: tenant_engine
  costAttributionKey: platform:tenant-engine
  clientNamespaces: [tenant-engine]
  roles:
    owner: tenant_engine_owner
    migration: tenant_engine_migrate
    runtime: tenant_engine_app
  limits:
    migrationConnections: 2
    runtimeConnections: 12
    statementTimeout: 30s
    idleInTransactionSessionTimeout: 15s
  tenantKeyingRequired: true
  tenantIsolation: consumer-service-boundary

Two things to raise with them rather than assume:

• tenantKeyingRequired: true is right for audit-core, whose rows are per-tenant. Ours are about tenants — tenant_id is the primary key of the tenants table, not a partition key on someone else's data. Confirm that their isolation tests read our shape correctly rather than flagging a false positive.
• Statement timeout. 30s is generous for this workload; every query here is a single-row lookup or a small transaction. A tighter timeout is a better failure mode for a service flex-auth calls synchronously on the authorization path — a slow query should fail closed fast, not hold the PDP.

Record what would trigger a move to dedicated, so the reversal is a judgement already made rather than one improvised under pressure. Candidate triggers: a noisy neighbour affecting the authorization path, a compliance or residency requirement, a plan tier that sells isolation, or the shared cluster's backup policy no longer fitting.

Also decide backups: whether the shared cluster's existing scheduledbackups policy covers us, or we need our own. SQLite-on-a-PVC had no backup story at all, so this is a gain to claim explicitly rather than inherit by accident — and a shared cluster means inheriting someone else's retention choice, which is worth checking rather than assuming.

Do not write a CNPG Database or Cluster manifest into this repo's deploy/. That surface belongs to rapp-postgres. Our deploy/ gains only the consumption side — how the workload reaches the leased credential.

Done when rapp-postgres has provisioned the consumer, the connection reaches the app only through an injected, refreshable credential, and the move-to-dedicated trigger list and runbook are recorded.

Status 2026-08-17: accepted. consumers/tenant-engine.yaml merged at deda11e. Provisioning is operator-gated as RAPP-IN-0004; nothing applied yet.

2026-08-18 repository readiness: desired runtime and migration manifests now consume separate file-projected leases, label the client namespace, and admit egress only to the real databases/platform-pg destination (an earlier draft incorrectly selected namespace railiance-platform). The published retention policy replaces the declaration's placeholder. T01 remains progress because consumer/lease provisioning and backup evidence are live operator gates.

They caught a real defect in our proposal. The declaration had a single statementTimeout field that the renderer applied to the migration role, the runtime role, and the database — so our 5s would have given us 5s DDL and failed the first non-trivial migration. Rather than reject it they made it expressible, adding limits.migrationStatementTimeout (defaulting to statementTimeout, so audit-core's rendered SQL is byte-identical). Ours is now statementTimeout: 5s / migrationStatementTimeout: 30s. The 5s runtime reasoning was accepted as-is.

Mechanical detail worth keeping: the database-level statement_timeout is what a leased login actually gets, because group-role settings do not pass through membership and OpenBao vends a fresh login role that merely inherits tenant_engine_migrate. The 30s therefore has to be set on the leased login in the migration role's creation statement. That lands in their OpenBao config — but if a migration ever dies at 5s, that is where to look.

tenantKeyingRequired: true confirmed correct. The field asserts our data is tenant-keyed from the first migration; nothing inspects the key's shape, and the isolation probes run against a synthetic consumer, so there was no audit-core-shaped assumption to trip. They queued a probe run with our consumer present anyway, on the grounds that "we do not think it will false-positive" is not evidence — which is the right standard.

Answers to the three open questions

Q1 — lease delivery: the credential directory is sanctioned. A ClusterSecretStore over OpenBao's database secrets engine projects the lease to a mounted path. Read the credential at connection checkout, not once at startup. Their rotation is overlap-first — acquire and verify the replacement, switch the pool, drain the old, revoke the predecessor — so a consumer that re-reads per connection rotates with no restart, while one that takes the lease as process environment needs a restart every rotation. They require that to be an explicit per-consumer choice; we take the directory.

There is also a broker exec path injecting PG* vars into a child process (railiance-platform/scripts/credential.py) — for reviewed migrations and operator sessions, not the runtime pod.

Theirs to create: ClusterSecretStore openbao-tenant-engine, and OpenBao roles rapp-postgres/tenant-engine-{runtime,migration} — bundled with audit-core's outstanding RAPP-IN-0003.

Ours to do: label the namespace railiance.io/postgres-client=platform-pg. Their consumer-ingress NetworkPolicy selects on that label, not on spec.clientNamespaces — the declaration field is review metadata, the label is enforcement. Done declaratively in deploy/tenant-engine.yaml's Namespace document rather than by an imperative kubectl label, so it cannot drift out of the repo.

Q2 — out-of-band migration is the contract, not a preference. The runtime role gets DML only and owns nothing; migrate-on-startup would require DDL on the runtime credential and collapse the separation. So our idempotent startup migration becomes a step run under a tenant-engine-migration lease before the new image serves traffic. Keep it idempotent regardless — that property is what makes a move to dedicated capacity a restore rather than a rebuild.

Q3 — backup is inherited and now real: continuous WAL archiving to Scaleway S3 (gzip), daily base backup at 02:15, 30-day retention, plus an encrypted logical dump lane to Nextcloud without PITR.

No certified RPO. Restore and PITR are proven against a scratch cluster and scratch object store, not the production serverName, so the honest status is "designed for minutes, not yet measured". They volunteered that rather than quoting a number they had not earned.

Two things to push back on

1. Dedicated capacity does not mitigate §5 for us. They offer a dedicated instance as the escalation for a consumer that cannot accept ADR-0001 §5's residual risk — a leaked tenant_engine_app credential reading and writing every row we own. For us that escalation does not work: a dedicated instance changes co-residency, not what our own runtime credential can reach. The blast radius is identical either way. So we should not argue for dedicated on §5 grounds; it would buy a different guarantee than the one at risk.

What §5 actually means here is worse than for audit-core, and worth stating plainly: direct DML bypasses every control this service exists to enforce — flex-auth authorization, version CAS, the guardrail loosening guard, and the audit trail. Someone with the runtime credential could grant PLTF on any tenant, or raise any ceiling, with no authorization check and no audit event. Since tenant-engine is the source of the tenant_roles claim key-cape mints and flex-auth reads live, that is privilege escalation across NetKingdom, not just data tampering. §4's opt-in RLS does not help: our rows are the tenants, so there is no per-tenant predicate to scope by.

The real mitigations are lease lifetime and network reach, both of which they provide — plus one we do not have, below.

2. Our audit trail is only as trustworthy as our own database. events lives in the same database as the rows it attests to, so the §5 scenario forges the evidence along with the data. That is a genuine gap, and the fleet already has the answer: audit-core exists as an append-only sink, and AUDIT_CORE_SENDERS implies a registration path. Emitting there would make our trail tamper-evident independently of our store.

Out of scope for this workplan — it is a new cross-service dependency, not a store migration — but it should not be discovered later. Raised with rapp-postgres; needs its own workplan.

RTO answer they asked for

They asked us to say now if our RTO on the authorization path cannot absorb a single-consumer restore (a logical dump taken from a scratch-restored copy of the whole instance, then a controlled import).

Split the cases, because the answer differs:

• Whole-instance loss: we are restored alongside everyone else. Acceptable, and dedicated capacity would make it worse by adding a second instance to recover.
• tenant-engine-only corruption — a bad migration, or the §5 credential scenario — needs the slow single-consumer path. This is the case that matters, and it is sharpened by our being the authority: there is no upstream to replay from. If our data is gone or forged, nothing else in the fleet can reconstruct it.

So the ask is not dedicated capacity but a per-consumer logical dump cadence. They already run an encrypted logical dump lane to Nextcloud; if it covers per-database dumps, our single-consumer restore comes from there rather than from a scratch-restored instance, and the slow path stops being the only path. Asked.

Completed 2026-08-21. Database/tenant-engine, the namespace admission label, exact-scope OpenBao runtime/migration roles, exact-namespace SecretStore and split ExternalSecrets are live. The runtime lease was forcibly refreshed without a pod restart, both local and live isolation suites passed 19/19, and the shared placement remains within the reviewed four-consumer ceiling. The move-to-dedicated triggers and honest backup/restore boundary remain recorded above. Live evidence is in rapp-postgres/docs/evidence/tenant-engine-postgres-cutover-2026-08-21.md.

T02 - Implement PostgresTenantStore

id: TEN-WP-0009-T02
status: done
priority: high
state_hub_task_id: "d7428bc1-2e5f-4a4c-93f5-9368ebb691d5"

Implement the full TenantStore Protocol — including guardrail_overrides / guardrail_changes / set_guardrail_override from TEN-WP-0006 — and add PostgreSQL to the conformance suites, which are already parametrised over in-memory and SQLite. A third backend should be a fixture parameter, not a new test file.

Invariants that must hold identically, not approximately:

• mutate_tenant() commits idempotency replay, version CAS, mutation, and audit event in one transaction;
• set_guardrail_override() does the same for the override, its audit record, and its receipt;
• a replayed Idempotency-Key short-circuits before the version check;
• reads and writes never observe a row mid-transaction.

That last one is where PostgreSQL should simplify rather than complicate: SQLite needed an explicit RLock around reads because one connection is shared across request threads, and the concurrent-writer test caught a real defect there. Postgres gives proper per-connection transaction isolation, so the lock should disappear rather than be ported. Do not transliterate the SQLite implementation — port the semantics and let the backend do what it is good at. Use a connection pool and appropriate isolation, and prove the guarantees with the same concurrent-writer test that caught the SQLite bug.

Adds a runtime dependency (psycopg); keep it out of the base install path if SQLite-only dev is meant to stay dependency-light.

Done when all three backends pass the same conformance suites unchanged.

Completed 2026-08-18. PostgresTenantStore implements the full protocol with bounded pooling, per-checkout credential-file rotation, row locking and atomic receipt/version/event transactions. The existing lifecycle and guardrail conformance suites run against PostgreSQL when TENANT_ENGINE_TEST_DATABASE_URL is present. A disposable PostgreSQL 16 run passed 88 shared conformance cases; the full source suite passes 260 with 28 environment-gated PostgreSQL cases skipped when no database is supplied.

T03 - Backend selection that fails closed

id: TEN-WP-0009-T03
status: done
priority: high
state_hub_task_id: "89c121c6-8bc5-4abe-80f0-d11406aeffc2"

Settings currently carries only database_path. Add a database URL and make selection explicit:

• URL set → PostgreSQL;
• path set → SQLite;
• both set → refuse to start. Do not silently prefer one. An ambiguous store configuration in production is exactly the class of silent misconfiguration this repo fails closed on everywhere else, and picking a winner would let a stale TENANT_ENGINE_DATABASE_PATH quietly shadow the real database;
• neither set → in-memory, as today, which is correct for tests and wrong for production.

Consider surfacing the active backend on /health. The last two production incidents were invisible because the service looked fine from outside; "which store am I actually using" is cheap to answer and expensive to guess.

Done when misconfiguration is a startup failure with a clear message, covered by tests.

Completed 2026-08-18. URL-file selects PostgreSQL, path selects SQLite, both refuse startup, and neither retains the in-memory test default. /health reports and pings the active backend so store selection and credential failure are externally visible without disclosing a DSN.

T04 - Migrate production data

id: TEN-WP-0009-T04
status: done
priority: high
state_hub_task_id: "51a83eae-9e9f-4676-bc1d-9c2d884bac0d"

Move the live SQLite database to PostgreSQL. Currently small — two tenants (tenant:trial:portalcheck active v1, tenant:trial:ten-wp-0005-t05 retired v5) plus the T04 disposables from TEN-WP-0007 — but small is not the same as trivial.

Everything must move, not just the tenants:

• tenants with versions and lifecycle timestamps preserved exactly — a reset version silently breaks every consumer holding an ETag;
• grants including revoked ones, because the trail is append-only and its history is the audit record;
• plans;
• events — the audit correlation contract;
• idempotency_receipts — dropping these lets an in-flight retry double-apply a mutation that already happened;
• guardrail_overrides and guardrail_changes.

SQLite is single-writer and the app writes to it, so the cutover must stop writes rather than race them: scale to zero, export, import, verify, then start against PostgreSQL. Verify by comparing row counts and spot-checking the two known tenants' versions and lifecycle state, not by trusting the exporter.

Keep the SQLite file and its PVC until T05's soak passes. It is the rollback.

Done when a verified copy is live in PostgreSQL and the comparison evidence is recorded here.

2026-08-18 repository readiness: tenant-engine-transfer now refuses a non-empty target, copies all seven tables in one transaction, preserves identity sequence values and nullable legacy timestamps, compares every source and target row, and emits non-secret counts/SHA-256 digests plus requested tenant lifecycle/version checks. Its PostgreSQL 16 integration test exercises all tables and the next event sequence. The live scale-to-zero/export/import is not performed and T04 remains progress.

Completed 2026-08-21. Writes were stopped before the source snapshot. The transfer verified all seven physical tables by exact row comparison and deterministic digest: 5 tenants, 13 events, 8 receipts, 3 guardrail changes, 1 override, and empty grants/plans. The known active v1 and retired v5 tenant records were unchanged. Two failed attempts rolled back to an empty target; the successful retry also proved the next event sequence. The stopped-write SQLite snapshot hash and full per-table digests are recorded in the linked rapp-postgres evidence.

T05 - Cut over the deployment

id: TEN-WP-0009-T05
status: done
priority: high
state_hub_task_id: "03aeae3b-5e0f-4c77-a763-787ae08078f5"

Update deploy/tenant-engine.yaml:

• drop the PVC and its volume mount;
• add TENANT_ENGINE_DATABASE_URL from the CNPG-minted secretKeyRef;
• switch strategy: Recreate → RollingUpdate, now that no ReadWriteOnce volume forces serialization — this is what unblocks TEN-WP-0008-T02's canary;
• extend the NetworkPolicy egress to the Postgres service, and no wider. Ingress stays restricted to user-engine.

Then decide, deliberately, whether to raise replicas above 1. It becomes possible here for the first time; possible is not the same as warranted, and a second replica changes failure modes for a service on the authorization path.

Update make verify-pin if the expected shape changes, and re-run it.

Rollback: re-pin the previous digest and re-attach the PVC. State plainly that this becomes lossy once writes have landed in PostgreSQL — after that point the rollback is "restore from Postgres", not "swap back to the file".

Done when production runs on PostgreSQL, make verify-pin passes, and the TEN-WP-0007 T04 verification list still passes end to end against the live service.

2026-08-18 desired state: PVC/mount removed, RollingUpdate selected, file-projected runtime and caller credentials added, and egress narrowed to databases/platform-pg, flex-auth and DNS. A separate migration Job has its own lease and NetworkPolicy. Replicas deliberately remain one. The manifests are not applied and the pinned old digest does not yet contain this code, so T05 remains progress and no live PostgreSQL claim is made.

Completed 2026-08-21. Production is healthy with backend postgresql at immutable digest sha256:a8e8086ffc5b772c1391b166f5e1884b90f7d327b152c205eceae129df555c24. The repo pin, Deployment spec and running image ID agree; make verify-pin and the package verify-live target passed. The Deployment is RollingUpdate, does not mount the SQLite PVC, keeps one deliberate replica, and retained all five required routes plus the TEN-WP-0007 guardrail/lifecycle checks. The old PVC is a time-bounded rollback artifact, not a current authority; its post-soak retirement is RAPP-IN-0005.

T06 - Tell the fleet, and close the loop on TEN-WP-0008

id: TEN-WP-0009-T06
status: done
priority: medium
state_hub_task_id: "e7adbc64-ad1b-4f28-bfd0-0b07034629db"

• flex-auth: availability characteristics of their data source changed. No contract or action change.
• user-engine: no contract change either, but they run the same CNPG pattern and may have operational lessons worth having before we repeat their mistakes.
• TEN-WP-0008-T02: record that the ReadWriteOnce canary constraint is gone, so staged-promotion onboarding no longer has to describe a canary that cannot run.

Done when the notes are sent and TEN-WP-0008-T02 is updated.

Completed 2026-08-21. Non-secret completion notices were sent to flex-auth (State Hub message 6bb6f923-8909-45d0-9c57-2b6d7c3e41ad) and user-engine (9512cf0c-f2f0-486b-a710-f737b9c79510), stating the availability/storage change and unchanged service contracts. TEN-WP-0008-T02 now records that the RWO constraint is gone and that side-by-side canary execution is storage-feasible.

Out of scope

• Removing SQLite. It stays as the dev and test backend, and as the thing that keeps TenantStore an honest seam.
• Schema redesign. Port the existing schema; a store migration and a model change at the same time makes any regression ambiguous.
• Sharing a database with user-engine. tenant_id is the only key the two services share, and it stays that way — separate stores are the boundary, not an implementation detail. Sharing a cluster is fine; sharing a database is not.
• Fleet placement policy. Which element or tenant gets dedicated capacity, and how isolation maps to plan tiers, is a platform decision. This workplan makes tenant-engine movable and stops there.
• Emitting the audit trail to audit-core. Identified under T01 as a real gap — our events table shares a database with the rows it attests to, so ADR-0001 §5 forges both together. It is a new cross-service dependency rather than part of a store migration. Live residual TEN-IN-0001 owns promotion into a reviewed workplan; it is no longer parked only in this prose.
• Per-tenant isolation. A future plan tier may sell dedicated infrastructure. tenant-engine already records plan assignment by id, and adaptive-pricing owns what a plan means, so neither the tier definition nor the placement that implements it belongs here. Worth designing for — which the portability principles above do — not worth building for.