Issue 067 — fold in the embedded-vs-provisioned axis

Naming which provider is only half of how a module gets a database. The other
half: a module may carry its own version/fork-pinned instance, module-network
only, no published port, not a provision — and the model has no word for it.
Add it as a second axis with its own open questions.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx
This commit is contained in:
2026-09-20 21:24:42 +02:00
parent 1ce9ffe79f
commit c4ff0478b7
@@ -59,6 +59,36 @@ provider, and a consumer has no field in which to choose.
Modelled as mesh-scoped, that topology is expressible only by accident. To carry
it deliberately the provision must be able to name its provider.
## A second axis: provisioned against a provider, or embedded and private
Naming *which* provider is only half of "how a module gets a database". There is a
second, distinct case the model also cannot express: a module that does **not**
consume a shared provider at all, but carries its **own** instance inside its own
composition — on its own module network, publishing no host port, visible to
nothing else in the mesh. This is legitimate and sometimes necessary: some
containers pin a database *server* version or need a fork or extension set (a
customised postgres, a vector extension) that the node's shared provider does not
offer, so they must run their own alongside the main container.
The distinction that matters:
- **Provisioned** — the module requires a provision and is bound to a *named
node-scoped provider* (the first axis above). This should be the default; on the
mesh being migrated onto, most per-module databases are vanilla servers on old
version pins that could simply be consolidated onto the node's shared provider.
- **Embedded and private** — the module ships its own instance because a fork or
version genuinely forces it. Its credential is still a mesh-generated secret, not
a module-authored password; but the *instance* is module-internal — same module
network only, no published port, **not registered as a provision**, so nothing
else can bind to it and it cannot collide on a well-known port.
The model has no word for the second case. A module that carries a private instance
looks, to the mesh, either like nothing (an undeclared container) or like a provider
it must not be treated as. "Embed only when a fork or version forces it; otherwise
provision against the node's provider" is the rule the design should be able to
state and check — and the invisibility of an embedded instance (own network, no host
port, not a provision) should be an enforceable property, not a convention.
## Open questions
- Where does the provider name live — on the provision definition (`scope: "node"`
@@ -76,3 +106,8 @@ provider, and a consumer has no field in which to choose.
- Does this interact with secret rotation (the issue-scope of `rotate`) — must
rotation address a specific provider's credential holders rather than "the
provision's"?
- When a module carries an **embedded, private** instance rather than consuming a
provider, how is that declared so the mesh knows it is module-internal — not a
provision, not published, not bindable by anything else — and can enforce it?
- What decides embed-vs-provision — is it the module's declaration alone, or may an
operator override at assignment (consolidate this one onto the node's provider)?