jschoubben
b69ae663bc
Issue 108: the artifact store has never collected anything. Fifty-three repositories on the machine that serves everything else, and the only outcome of leaving it is a full disk reported as somebody else's failure. The mesh decides what may go — from its own build records, so it never names a digest it did not put there — and the store reclaims the bytes in a nightly window with its server held still. Deletion on the one door takes nothing a push did not already have. Designs 18 and 20 amended; issue 108 resolved. Also issue 202, found running the controller's suite: a module whose required setting nobody set is left out of the machine in silence, and dnsmasq became that module this morning.
68 lines
3.9 KiB
Markdown
68 lines
3.9 KiB
Markdown
---
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status: open
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opened: 2026-10-02
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located-in: [mesh-catalog modules/dnsmasq, mesh-controller cmd/mesh-controller]
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fixed-by:
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amended-design:
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---
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# 202 — A module whose required setting nobody set is left out of the machine, and the resolver is the module it happened to
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## What was observed
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Running the controller's own test suite against the catalogue beside it, 2026-10-02.
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`TestTheResolverIsToldEveryMachineOnTheNetworkAndToldAgainWhenOneLeaves` fails with *"the resolver
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was not handed the machines"*. Composing the same machine by hand and listing what it receives
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shows why: **dnsmasq contributes nothing at all.** Four resources are composed for that node, all
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of them the overlay's. The resolver's package, its configuration, its service and the fact that
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carries every machine's name are simply not there.
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The cause is one line added to `dnsmasq`'s configuration earlier the same day: the addresses it
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listens on beside the machine's own became an operator setting,
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`listen-address=${setting:listen-addresses}`, with no default. A `${setting:…}` nothing sets is
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refused, a module that cannot be composed is **left out** rather than failing the whole machine
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([ADR 0163](../../02-DECISIONS/0163-taking-a-module-over-is-a-comparison.md)), and so a node
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assigned the resolver is handed a declaration with no resolver in it.
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The failing test is the symptom that surfaced it. The test is not what is wrong.
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**Proven rather than inferred.** Composing the same machine a second time with
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`listen-addresses` set to `127.0.0.1` and nothing else changed, every one of dnsmasq's eight
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resources appears — `needs-broker`, `mesh-state`, `package`, `config`, `runtime-dns`, `runtime`,
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`service` and `fact-node-zones`. The only difference between a machine with a resolver and a
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machine without one is whether somebody set a value that did not exist yesterday.
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## Why it matters beyond this instance
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**Leaving a module out is right, and being quiet about it is not.** The rule exists so one
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module's broken setting cannot stop a machine converging — a good rule. But the outcome here is a
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machine that applies cleanly, reports current, and is missing its DNS resolver. Every name on that
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machine then resolves through whatever was there before, or not at all, and nothing in the mesh
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says the resolver was dropped. That is the shape
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[issue 152](../152-a-nodes-plan-failure-silently-drops-its-routed-names/00-report.md) records for
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routed names, here for a whole module.
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**And a setting with no default is a definition that cannot be assigned.** Every other
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`${setting:…}` in the catalogue names something that is genuinely particular to one installation —
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a public domain, an issuer. "Which addresses besides my own do I answer on" has an obvious correct
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default for every machine that is not a LAN gateway: none beside loopback. A definition that
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refuses to compose until somebody sets a value most machines do not need is a definition that
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breaks the next node to be assigned it, and genesis with it.
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## What this does not claim
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Whether the live machines are affected was not checked — those four have had the setting set, or
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their resolvers would already be gone. The claim is about a machine assigned the resolver *from
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now on*, and about the silence.
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## Open questions
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- Should the declaration say which modules it left out, where a person or the console can see it?
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`left_out` already travels to the host ([ADR 0163](../../02-DECISIONS/0163-taking-a-module-over-is-a-comparison.md));
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what is missing is anything that reads it back and says so.
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- Should a `${setting:…}` be allowed a default in the definition — making "unset" mean "the
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default" rather than "refuse" — or is a setting with a default no longer the operator's value?
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- Is leaving a module out ever right for a module a node is **assigned**, as opposed to one it
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merely pulls in? An assignment is somebody saying *this machine runs this*; silently not running
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it is the one answer nobody asked for.
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