Files
hq/04-ISSUES/202-a-module-whose-required-setting-is-unset-is-silently-left-out/00-report.md
T
jschoubben b69ae663bc ADR 0189: the store keeps what the records name, and a maintenance step holds its writers still
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.
2026-10-02 21:48:48 +02:00

3.9 KiB

status, opened, located-in, fixed-by, amended-design
status opened located-in fixed-by amended-design
open 2026-10-02
mesh-catalog modules/dnsmasq
mesh-controller cmd/mesh-controller

202 — A module whose required setting nobody set is left out of the machine, and the resolver is the module it happened to

What was observed

Running the controller's own test suite against the catalogue beside it, 2026-10-02. TestTheResolverIsToldEveryMachineOnTheNetworkAndToldAgainWhenOneLeaves fails with "the resolver was not handed the machines". Composing the same machine by hand and listing what it receives shows why: dnsmasq contributes nothing at all. Four resources are composed for that node, all of them the overlay's. The resolver's package, its configuration, its service and the fact that carries every machine's name are simply not there.

The cause is one line added to dnsmasq's configuration earlier the same day: the addresses it listens on beside the machine's own became an operator setting, listen-address=${setting:listen-addresses}, with no default. A ${setting:…} nothing sets is refused, a module that cannot be composed is left out rather than failing the whole machine (ADR 0163), and so a node assigned the resolver is handed a declaration with no resolver in it.

The failing test is the symptom that surfaced it. The test is not what is wrong.

Proven rather than inferred. Composing the same machine a second time with listen-addresses set to 127.0.0.1 and nothing else changed, every one of dnsmasq's eight resources appears — needs-broker, mesh-state, package, config, runtime-dns, runtime, service and fact-node-zones. The only difference between a machine with a resolver and a machine without one is whether somebody set a value that did not exist yesterday.

Why it matters beyond this instance

Leaving a module out is right, and being quiet about it is not. The rule exists so one module's broken setting cannot stop a machine converging — a good rule. But the outcome here is a machine that applies cleanly, reports current, and is missing its DNS resolver. Every name on that machine then resolves through whatever was there before, or not at all, and nothing in the mesh says the resolver was dropped. That is the shape issue 152 records for routed names, here for a whole module.

And a setting with no default is a definition that cannot be assigned. Every other ${setting:…} in the catalogue names something that is genuinely particular to one installation — a public domain, an issuer. "Which addresses besides my own do I answer on" has an obvious correct default for every machine that is not a LAN gateway: none beside loopback. A definition that refuses to compose until somebody sets a value most machines do not need is a definition that breaks the next node to be assigned it, and genesis with it.

What this does not claim

Whether the live machines are affected was not checked — those four have had the setting set, or their resolvers would already be gone. The claim is about a machine assigned the resolver from now on, and about the silence.

Open questions

  • Should the declaration say which modules it left out, where a person or the console can see it? left_out already travels to the host (ADR 0163); what is missing is anything that reads it back and says so.
  • Should a ${setting:…} be allowed a default in the definition — making "unset" mean "the default" rather than "refuse" — or is a setting with a default no longer the operator's value?
  • Is leaving a module out ever right for a module a node is assigned, as opposed to one it merely pulls in? An assignment is somebody saying this machine runs this; silently not running it is the one answer nobody asked for.