jochen
c4d9b515ea
A path inside a container is not a fact about the machine — /run/secrets and the directory a server keeps its data in are the software's own contract, true in any mesh that runs it. Only the host side of a mount names where it landed. The first sweep matched path-shaped strings, so it counted both halves of every mount and every in-container location a value mentioned: 798. Counted by role — directory and file resources, the host side of mounts, accesses, and the targets of binds, grants, receives and secrets — it is 698 across 70 definitions.
114 lines
6.8 KiB
Markdown
114 lines
6.8 KiB
Markdown
---
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status: located
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opened: 2026-09-26
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located-in: [mesh-controller internal/catalogue/declaration.go, mesh-catalog modules/keycloak, mesh-catalog modules/minio, mesh-catalog modules/nextcloud]
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fixed-by:
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amended-design:
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---
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# 122 — A module cannot ask for its own public name, so three manifests wrote this mesh's names into the catalogue
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## What was observed
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Reviewing the open module changes on 2026-09-26, three of them independently put a name belonging to
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**one particular mesh** into a module definition, each for a different piece of software and each as
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the only way to make the software work:
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- The identity provider's manifest gains `KC_HOSTNAME: https://<label>.<public-domain>` as a literal,
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because the software generates absolute URLs and, behind a proxy, cannot derive them.
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- The object store's manifest gains `MINIO_BROWSER_REDIRECT_URL: https://<label>.<public-domain>` as
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a literal, for the same reason — its console redirects to an absolute URL.
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- The file-sync module's S3 bucket is renamed from `nextcloud` to a name carrying this mesh's own
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name, so the module matches a bucket that already exists here.
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No reviewer introduced these carelessly: each is the value the software needs, and there is nowhere
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else to put it.
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**And they are not the first.** Asked whether merging them would set a precedent, the catalogue
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answered no: **five modules already on the main branch carry one**. The clearest is the workflow
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automation module, whose environment file states its host, its protocol and a full absolute webhook
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URL as literals; two more — the proxy and the builder — carry a complete clone URL for a repository
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on this mesh's own forge, scheme, host and port included.
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**Counted properly, 2026-09-26.** The five were what a first look found. A sweep of all 71
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definitions, for values that could only be true of one installation:
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| What is named | Occurrences | Modules |
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|---|---|---|
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| A public domain, or a name under one | 49 | 26 |
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| The node's own name | 58 | 19 |
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| A routable IP address | 12 | 1 |
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| A **host** path — where a file sits on the machine | 698 | 70 |
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| An email address | 0 | 0 |
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The path row is [issue 119](../119-a-module-definition-decides-where-its-files-live/00-report.md),
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counted again — and counted differently, which is the correction worth keeping. **A path inside a
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container is not a fact about the machine.** `/run/secrets/…` and the directory a server keeps its
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data in are the software's own contract, true in any mesh that runs it; only the host side of a mount
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names where it landed. The first sweep matched path-shaped strings and so counted both halves of every
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mount and every in-container location a value mentioned. Counted by role instead — directory and file
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resources, the host side of mounts, accesses, and the targets of binds, grants, receives and secrets —
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it is 698 across 70 definitions. Issue 119's own figure is role-counted already and close to this; it
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additionally counts paths written into environment values, a few of which are container-side.
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The rest of the table is this issue. **Thirty of the seventy-one definitions name this
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installation** in one of the first three ways, and the worst single case is not a domain at all: a
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mail module states the node's own public IPv4 as the address it trusts a real-IP header from, so a
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node that moves, or gains a second address, silently stops attributing mail to the right sender. A
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private subnet, the mail domain, the site name and the administrator's domain sit in the same block
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of values.
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Two upstream resolvers are excluded from the count deliberately: naming a public DNS service is a
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policy default, true of any mesh that wants it, not a fact about this one.
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So the three under review are the visible edge of a pattern the catalogue already follows, which
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changes what this issue is for. It is not a matter of refusing three changes; there is no version of
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this catalogue today that does not name the mesh it was written in, and a mechanism is the only
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thing that removes any of them.
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## What the mesh offers instead, and why none of it answers
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A manifest may interpolate `${secret:…}`, `${seat:…}`, `${bound:…}`, `${port:…}` and
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`${machine:…}`. The machine form resolves `at`, `name` and `address` — the machine's identity on the
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**private** network. None of them yields a public name.
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The mesh does compose public names: a route contribution's label is joined to the node's public
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domain, `<label>.<public-domain>`, and the mesh interprets neither half. That happens inside the
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controller when a declaration is built, and the result reaches the proxy that serves the route. It
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does not reach the module that asked for the route, so a module that must **tell its own software**
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what it will be reached at cannot read what the mesh already worked out.
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So the workaround is the only expressible option: write the answer down, in the definition, for the
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one mesh it is true of.
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## Why it matters beyond these three
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A module definition is meant to hold what is true of the module everywhere, with everything
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particular to an installation resolved at assignment — the argument
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[ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md) (proposed)
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makes in full, and what [issue 119](../119-a-module-definition-decides-where-its-files-live/00-report.md)
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found for paths. A hostname is the same kind of fact as a path, and arriving by the same route: not
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because anyone disagreed with the principle, but because the mechanism that would honour it does not
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exist yet.
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The cost is concrete. A second mesh installing the identity provider from this catalogue gets the
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first mesh's hostname, and its login flow breaks in a way that looks like a proxy fault. Nothing
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checks for it: a literal hostname in an env value is a well-formed string, and no rule distinguishes
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it from a version number.
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The bucket case is the same shape with a different subject — an adopted resource's real name is also
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particular to one installation, and also has nowhere to live but the definition.
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## Open questions
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- Should a module be able to name what it will be reached at — a `route`-scoped interpolation
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resolving to the composed public name of a route it contributes, so the answer the mesh already
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computes is the one the software is told? That is the smallest fix and it stays within the existing
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vocabulary.
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- Does the scheme belong to it? Every instance here wrote `https://`, which is true of a route the
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proxy terminates and not of the module's own port.
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- For an adopted resource such as an existing bucket: is that a setting on the assignment (where
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ADR 0112 would put it), and if so what reads it — the provisioner, or the module's own values?
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- What check would notice the next one? A definition naming a public domain is detectable in the
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shape of the value, which is more than nothing, and less than a rule.
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