railiance-platform/docs/rapp-platform-service-pattern.md

# The S3 Platform-Service Rapp Pattern

Date: 2026-08-11
Owner: `railiance-platform` (S3)
Work record: `RAILIANCE-WP-0015-T01`

## Purpose

This is the reference shape for packaging a **platform service** as a `rapp-*`
managed workload package. It generalizes the two boundaries S3 has already
drawn — `docs/rapp-openbao-boundary.md` and `docs/rapp-postgres-boundary.md` —
so the third and fourth platform rapps do not each re-derive the split from
scratch.

It is deliberately *not* a general rapp standard. The four-axis repo family
model belongs to `railiance-master/docs/repository-axes.md`, and the
`rapp.yaml` schema and canon promotion are in flight there and in
`the-custodian`. This document covers only the half S3 owns: what a
platform-service rapp looks like, and where the line falls between the package
and the platform.

## The rule

> A rapp owns how its workload is **packaged, deployed, verified, rolled back
> and recovered**. S3 retains everything that is **true across workloads**:
> policy, credential custody, lane approval, and the shared substrate the
> package assumes.

Both existing platform rapps already state this in their own words. From
`rapp-openbao-boundary.md`: the package may own how OpenBao is packaged,
deployed, verified and skinned, and must not become the home for platform-admin
policy, workload KV lane policy, delegated metadata authority, or credential
grants. From `rapp-postgres-boundary.md`: the package owns manifests, consumer
declarations, provisioning surface, isolation tests and recovery, while S3
retains the operator, storage policy, backup target and the credential-broker
grant catalog.

## The ownership test

When an asset's home is unclear, ask in this order. The first answer that
applies decides it.

1. **Would this asset survive replacing the workload with a different product?**
   If yes, it is S3's. Credential lane approval survives swapping OpenBao for
   another secrets engine; an OpenBao Helm values file does not.
2. **Does any other workload depend on this asset?** If yes, it is S3's. A
   `workload-kv-read-*` policy is consumed by the workload it names but governed
   by a lane model shared by all of them.
3. **Does it encode who may approve, not how to apply?** Approval authority is
   S3's; application mechanics are the package's. This is the line that keeps a
   rapp from becoming a shadow S3 repo — the failure mode named explicitly in
   `railiance-master/docs/rapp-first-wave-candidates.md`.
4. **Otherwise it is the package's.** Charts, values, overlays, deploy and
   verify scripts, workload-specific smoke and recovery procedure, and the
   Makefile targets that drive them.

### Applied

| Asset class | Home | Test |
| --- | --- | --- |
| Helm values, chart pins, overlays, ingress/middleware manifests | rapp | 4 |
| Deploy / dry-run / status / verify / rollback commands | rapp | 4 |
| Workload-specific smoke and recovery procedure | rapp | 4 |
| Consumer declarations and provisioning surface | rapp | 4 |
| Operator and read-only policy surface | S3 | 1 |
| Credential lane approval, CCRs, grant catalog | S3 | 3 |
| Cross-workload secret delivery (ESO, KV lanes) | S3 | 2 |
| Backup target procurement and its credentials | S3 | 1 |
| Storage class, monitoring substrate, cluster access | S3 | 1 |

## Reference `rapp.yaml` for a platform service

Pending the normative schema from `railiance-master`, a platform-service rapp
should carry at least the following. Fields marked † are the consistency fields
currently present in `rail.yaml` and `rapp-qonto` but missing from both platform
rapps; `RAILIANCE-WP-0015-T02` adds them once the schema settles.

```yaml
kind: managed-workload-package
repo_family: rapp
rapp_id: rapp-<workload>
repo: rapp-<workload>
ownership_repo: railiance-platform      # the S3 home retaining governance
contract_version: 1.0.0                 # †
readiness_state: verified               # †
data_classification: <internal|restricted>   # †
criticality: <high|critical>            # †
workload_identity:
  name: <workload>                      # the workload, never the repo name
  package_type: helm-managed-platform-service
  chart: <repo/chart>
  chart_version: <pinned>
  app_version: <pinned>
primary_rail: rail-kubernetes
supported_rails: [rail-kubernetes]
runtime_dependencies: [...]             # what must exist for this to run
rollout_contract: {...}
smoke_contract: {...}
rollback_contract: {...}
source_documents: [...]
```

Two conventions worth stating because they have already drifted:

- `workload_identity.name` is the **workload**, not the repo. `openbao`, not
  `rapp-openbao`.
- `ownership_repo` is the repo that retains governance after extraction — for
  platform services that is `railiance-platform`, and it is not the same thing
  as the repo the package was carved out of.

## Grouped rapps

Operator decision of 2026-08-11: rapp granularity is **grouped by bounded
context** — one rapp per cohesive group of services that deploys, versions and
rolls back together, rather than one rapp per deployable.

For a grouped rapp:

- members **must** be declared explicitly; an undeclared bundle is not a rapp,
  it is a drawer
- grouping is legitimate **only** where members share rollout and rollback fate.
  If one member can be rolled back without the others, it is a separate rapp
- the group's smoke contract must cover the group, not just its largest member

`rapp-postgres` is already a grouped package in this sense — it owns the CNPG
cluster manifests plus per-consumer declarations, and declares its consumers
explicitly in `consumers:`. That is the shape to copy.

## Credential lanes

A platform-service rapp never owns credential custody. It declares what it
needs; S3 vends it through the existing broker. The binding between a rapp's
`runtime_dependencies` / `secret_references` and the S3 grant catalog and CCR
lanes is specified in `RAILIANCE-WP-0015-T06` — until that lands, follow
`docs/credential-broker.md` and `docs/credential-change-approval.md` directly
and do not create a package-local lane.

The existing rule holds without exception: the package never commits
credentials, and a workload receives a short-lived lease through the platform
broker rather than a package-managed secret.

## When a platform service earns a rapp

Not every S3 service needs one. A platform service is ready for extraction when
it has a stable workload identity, a package surface already visible in Git, an
explicit dependency and secret story, and described deploy/verify/recover
behavior — the criteria from `rapp-first-wave-candidates.md`. A service that
fails these is not blocked from being operated; it simply stays owned by S3
until its packaging identity stops moving.