hq/04-ISSUES/056-an-adopted-module-assigned-to-a-second-node-raises-a-second-server/00-report.md

status, opened, located-in, fixed-by, amended-design

status	opened	located-in	fixed-by	amended-design
resolved	2026-09-17	mesh-controller mesh-host	mesh-catalog + mesh-controller (the foundation modules claim mesh-scoped seats)	02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md

056 — An adopted module assigned to a second node raises a second server

Symptom

The store and broker are adopted in place (ADR 0078, issue 051): genesis raises mesh-store/mesh-broker on the control-node, and assigning the postgres/lavinmq module there makes the module reconcile the already-running container instead of raising a new one. Adoption works because the container is already running on that node.

Nothing stops the same module being assigned to a second node. On a node where no mesh-store is running, the applier finds no container by that name and raises one — a second postgres, a second broker. The whole point of Phase 3 — "one postgres, one lavinmq" — holds only by the convention that genesis assigns these modules to the control-node alone; it is not enforced.

Why it matters

"There is one store and one broker" is stated as a property of the mesh, and a property enforced by nothing is indistinguishable from a wrong one. A single extra assign — the ordinary verb an operator types — silently produces a divergent second server holding none of the first's data, and consumers resolved to it get an empty store. The failure is silent and far from its cause.

The exclusive foundation modules are the mesh's clearest case of "there is one of me," yet unlike a mesh-scoped seat, an adopted module carries no claim that the resolver would refuse a second holder for.

Open questions

• Should postgres/lavinmq claim a mesh-scoped exclusive seat (the way mesh-controller claims the-controller), so the resolver refuses a second assignment by the same mechanism that keeps one controller?
• Or should adoption be explicit — a module that adopts a foundation container declares it, and the controller refuses to place it on a node whose foundation did not raise that container?
• How is "one postgres, one lavinmq" checked, rather than assumed — in the resolver, in status, or in a bed that tries the second assignment and asserts the refusal?

Resolution (2026-09-17)

The foundation modules now claim a mesh-scoped seat named after the server each guards — postgres claims mesh-store, lavinmq claims mesh-broker, and the controller's seat is renamed the-controller → mesh-controller so all three follow one convention (ADR 0079). The resolver's checkClaims refuses a second holder mesh-wide — the same mechanism that keeps one hub and one controller — so a second assign is a refusal at resolution (one per mesh), not a silent second server.

Checked by TestAFoundationModuleCannotBeRaisedOnASecondNode (each foundation module's second assignment is refused) and by the manifests declaring the seat; the two-node adopted-broker bed stays green with the seats in place, so the claim does not break single-node adoption.