hq/01-RESEARCH/015-the-object-store-after-minio/00-overview.md

---
status: active
initiated: 2026-09-24
touches:
  - 02-DECISIONS/0028-the-substrate-supplies-the-control-plane-and-nothing-else.md
  - 02-DECISIONS/0033-the-substrate-is-a-store-and-a-broker.md
  - 02-DECISIONS/0048-a-provider-creates-the-credential-the-mesh-minted.md
  - 02-DECISIONS/0049-a-consumers-identity-fits-the-tightest-backend.md
  - 02-DECISIONS/0078-the-store-and-broker-are-modules.md
  - 02-DECISIONS/0084-which-provider-serves-a-consumer.md
  - 03-DESIGN/00-as-is/03-provisioning.md
  - 03-DESIGN/01-to-be/07-the-foundation.md
  - 04-ISSUES/113-the-object-stores-images-were-withdrawn-upstream/00-report.md
---

# 015 — The object store after MinIO: which S3 implementation, and how the data moves

**The question.** The mesh's object store is MinIO. Its community edition is archived upstream,
its server and client images have been deleted from every public registry, and the pinned release
is four and a half years old and will never be patched
([issue 113](../../04-ISSUES/113-the-object-stores-images-were-withdrawn-upstream/00-report.md)).
Which S3-compatible implementation replaces it, and what is the migration track for the data and
the provisioning model that sit on top of it?

**Why now, and why not sooner.** Nothing is on fire: nodes that already hold the images keep
running, and issue 113 establishes that the deploy path tolerates an unfetchable-but-present
image by design. The forcing function is not an outage but a one-way door — **no node that does
not already hold the images can ever provision the module again**, so the mesh's ability to stand
a node up from its declarations is already broken for this module, and silently.

**The direction is not a departure from the design; it is the design.** The foundation document
already states the commitment:

> The dependency is on the **protocol**, not the product: AMQP for the bus, S3 for the object
> store, the OCI protocol for the registry. That is what keeps the naming safe rather than a
> commitment that cannot be revisited.

The object store is also **not** a foundation service — ADR 0028 removed it, and it is an
ordinary module required through the module graph by whatever wants one. (The "exception that is
not a swap" in that passage is the relational store, whose provisioning model borrows PostgreSQL's
own meaning of databases, roles and schemas. The object store carries no such coupling: a bucket
is a bucket.) So this effort is an instantiation of an existing principle, not a redesign — which
is the cheapest kind of decision to make and the strongest kind to cite.

## What the replacement has to carry, measured

Taken from the module's manifest, its composition, its tool surface, and a search for its
consumers across the catalogue — not from assumption.

| Requirement | Evidence in the module today |
|---|---|
| S3 API | The protocol every consumer speaks; already the design's stated dependency. |
| **OIDC login against the mesh's identity provider** | Six configuration variables are wired and populated in practice — discovery URL, client id, client secret, scopes, display name, redirect — plus a dedicated entrypoint script that blocks startup until the provider answers. This is live, not aspirational. |
| Erasure-coded multi-node topology | Four server nodes with two data directories each, behind a load balancer. |
| A single-node form | Declared as a flavour, for development and small nodes. |
| Buckets as a typed provision | The module declares a provision type of `bucket` on a named network; the mesh mints the credential and the provider creates it (ADRs 0048, 0084). |
| A tool surface | Bucket create/list/delete, object list/info/delete, presigned URL, and provisioning. |
| A console | Published on its own subdomain through the reverse proxy, with an unlimited request-body middleware for uploads. |

**Consumers, counted:** one application module, one capture module that takes a private bucket per
node, one workflow module's tools, and the delivery/rescue internals of the shared library. The
surface is small — the cost is concentrated in the provisioning handler, the tool handlers and the
OIDC story, not spread across the catalogue.

## Candidates

**The comparison is open across three candidates.** It was briefly narrowed to SeaweedFS; that
narrowing did not survive measurement and was reopened on 2026-09-24. The evidence, the full
requirement-by-requirement table and what each option costs are in
[01 — the candidates measured](01-candidate-comparison.md).

In short, and only in short:

- **SeaweedFS** — Apache-2.0, the longest field record, erasure coding. Its **console OIDC is an
  Enterprise feature**; the free build authenticates the console with a local username and
  password. This is what falsified the original narrowing.
- **Garage** — the best match for how the mesh provisions, with a first-class admin REST API
  scoped to exactly bucket and key creation. Costs: replication rather than erasure coding, no
  full S3 endpoint span, and neither console nor identity integration.
- **RustFS** — the only candidate preserving the live behaviour, with a MinIO-shaped console and
  documented OIDC against Keycloak, under Apache-2.0. Costs: it reached GA eight days before this
  was written, and an open defect is reported in the credential path the mesh's bucket provision
  depends on.
- **Ceph RGW** — remains rejected as disproportionate where the object store is an ordinary
  module rather than a platform.

**The question that decided the original narrowing has been answered** — SeaweedFS's console OIDC
is not in the free build — and the answer was *"no candidate preserves the current feature set
for free"*, exactly the outcome this effort said was possible. The decision is therefore not
which product is best in the abstract but **which cost is acceptable**, and two measurements
gate it: whether an authenticating proxy is an acceptable answer to console single sign-on, and
which S3 endpoints consumers actually call. Both are named in
[01](01-candidate-comparison.md#what-is-still-unmeasured). Nothing graduates before them.

## The migration track, in outline

Data movement is the easy half, and deliberately reversible.

1. **Stand the replacement up beside the incumbent**, on its own ports and its own provision type.
   No downtime, nothing removed.
2. **Copy bucket by bucket with a neutral tool.** `rclone` rather than the incumbent's own client
   — the client has been withdrawn upstream too, so building the migration on it would inherit
   the same dependency this effort exists to remove.
3. **Verify per bucket** — object counts and checksums, not a transfer exit code.
4. **Repoint consumers through the connection the module already publishes.** Consumers read an
   API URL from the module's declared connections rather than addressing the store directly, so
   the cutover surface is that value plus the provisioning and tool handlers.
5. **Freeze writes, final incremental sync, flip**, and keep the incumbent read-only as the
   rollback until confidence is earned.
6. **Retire**, and only then remove the module.

The genuinely new work is not the copy. It is the **provisioning handler** and the **tool
handlers**, which are written against MinIO's admin API, and the OIDC wiring.

## Open questions

- How much of the OIDC requirement survives, and in which build? See above — this gates the
  choice.
- Does the mesh's bucket provision translate to the candidate's identity model without weakening
  what ADR 0049 says about a consumer's identity fitting the tightest backend?
- Should this effort also answer issue 113's general question — mirroring third-party images into
  the mesh's own registry — or is that a separate decision? Replacing one withdrawn product with
  another unmirrored upstream leaves the same one-way door in place, just further from the hinge.
- Is the four-node erasure-coded topology still warranted, or was it inherited? Worth re-asking
  while the product is being chosen, rather than reproducing a shape by default.