jschoubben
941b920bd7
Measured live. All four machines run the identical host binary — same digest, installed within eighteen seconds — and at first only one reported a version, which read as a difference where there was none. A machine publishes a report after an apply. The five-minute reconcile publishes nothing, because it is the machine keeping itself as declared rather than answering anything. So a current, idle machine never says, and the mesh cannot tell that from a machine running something ancient. Confirmed by pushing: not reported, then 04a27ca. Enough for the purpose, not enough for the claim. For deciding whether a new declaration field is safe it is sufficient — pushing is what the mesh is about to do, and the answer arrives with the act. For knowing what the mesh runs it is not, and "not reported" is worded as "nobody has asked recently" for that reason. Making a heartbeat carry it would close the gap and would change what a heartbeat is — a bare word that the node is there, deliberately carrying nothing else. Left alone rather than widened in passing.
101 lines
5.2 KiB
Markdown
101 lines
5.2 KiB
Markdown
# 087 — resolved: the mesh knows which host runs a machine
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*2026-09-30.*
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## The field existed and was thrown away on arrival
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The machine has reported its host version since
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[ADR 0141](../../02-DECISIONS/0141-the-host-delivers-its-own-successor.md) — `Host` on the report, with
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a comment saying why it must be there: *"without it nothing can say a machine is behind."*
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**The controller's own copy of the report did not have the field.** Two structs describe one message,
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one on each side of the wire, and only the sending side had it — so it unmarshalled into nothing and the
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mesh could not answer a question the machine had been answering for a week. That is the whole of this
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issue's mechanism, and it is worth stating plainly because neither side was wrong on its own.
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## What it says now
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`node show` names it per machine:
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```
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last heard from here
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host 2026-09-30-0214
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```
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`not reported — this machine has not said since the mesh began keeping it` where the mesh has not been
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told, because a machine that has not said is a different thing from a machine running nothing.
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`status` names the machines that are behind another:
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```
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1 machine(s) run an older host than another machine does:
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ace 2026-09-29-0113
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the newest any machine reports is 2026-09-30-0214. A host refuses a declaration carrying a
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field it does not know, whole — so a new field reaches these machines last
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```
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## Disagreement, not staleness, and that is deliberate
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The open questions asked whether the controller should refuse to send a declaration a node cannot
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parse. It cannot yet, honestly: **nothing delivers a host version** (ADR 0141 is accepted and not
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built, which is [issue 142](../142-the-host-is-the-one-thing-the-mesh-does-not-deliver/00-report.md)),
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so the mesh holds no canonical current version and "behind" has no fixed point to be behind.
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What it can say truthfully is that these machines do not all run the same host, and which is newest of
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the ones it has been told about. That is the fact that matters before a declaration gains a field: **the
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oldest host in the mesh is what the mesh may send.**
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Two deliberate refusals to guess:
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- **A machine that has reported nothing is not called behind.** It may be running anything. `node show`
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says it has not said, per machine, which is the honest form.
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- **Versions compare as strings.** That suits the timestamps and commits this mesh uses and is wrong
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for a scheme where `10` sorts before `9`. Said in the code at the place that would have to learn,
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rather than left as a surprise.
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## Measured on the mesh, and one limitation it exposed
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All four machines run the identical host binary — same digest, installed within eighteen seconds of each
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other — and at first only one reported its version. The other three said *not reported*, which read as a
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difference between machines where there was none.
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**A machine states its host version only when the mesh sends it a declaration.** The report is published
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after an apply; the periodic reconcile that runs every five minutes publishes nothing, because it is the
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machine keeping itself as declared rather than answering anything. So a machine that is current and idle
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never says, and the mesh cannot distinguish that from a machine running something ancient.
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Confirmed by pushing: before, `not reported`; after, `04a27ca` — the same version the machine that had
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been pushed already reported.
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```
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novox host 04a27ca
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shanks host 04a27ca
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g14 host 04a27ca
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ace host not reported — this machine has not said since the mesh began keeping it
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```
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`ace` has not been pushed since the field existed; it is adopted and parked.
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**This is enough for the purpose and not enough for the claim.** For deciding whether a new declaration
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field is safe it is sufficient, because pushing is what the mesh is about to do anyway and the answer
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arrives with the act. For *knowing what the mesh is running*, it is not: a long-idle machine's entry is
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as old as its last push, and the honest reading of `not reported` is "nobody has asked recently" rather
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than "this machine is silent". The words say the first, which is why they are those words.
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Making a heartbeat carry it would close the gap and is a change to what a heartbeat is — a bare word
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that the node is there, deliberately carrying nothing else. Left alone rather than widened in passing.
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## The open questions, answered as far as they can be
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- *Should a node report the version of its host?* It already did. The gap was the reading.
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- *Should the mesh refuse to send a field no node understands yet, or refuse per node and say so?*
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Neither, yet — refusing needs the mesh to know which fields need which version, which is the third
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question below and is not answered here. What it does is make the disagreement visible before
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somebody adds a field.
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- *Is there a general shape — a declaration saying which version of the host it needs?* Still open, and
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now cheaper to answer: the versions are recorded, so a minimum-version field on a declaration has
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something to compare against. It belongs with
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[issue 107](../107-a-declaration-carries-no-order/00-report.md), which wants to add a field and is the
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first thing this makes safe.
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