jschoubben
780c2b6e58
Rule 5 of ADR 0163 (a former target is removed) met issue 162 (an archive has no removal) in the host's own archive, the first time a host carrying former targets replaced itself; every machine applied nothing from then on.
65 lines
3.7 KiB
Markdown
65 lines
3.7 KiB
Markdown
---
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status: located
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opened: 2026-10-02
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located-in: [mesh-host internal/apply (removeOrphan: a former target of a kind with no removal was fatal), mesh-host internal/store (Record keeps a former target for every kind, the host's own archive included)]
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fixed-by:
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amended-design:
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---
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# 194 — The host's own former archive stops every machine applying anything
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## What was observed
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2026-10-02, 00:34Z, on all four machines of this mesh, the first time a host carrying former
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targets ([ADR 0163](../../02-DECISIONS/0163-taking-a-module-over-is-a-comparison.md), rule 5,
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built in mesh-host 63) replaced itself with a newer host (mesh-host 64).
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The host delivers its own successor as an archive whose target is a versioned directory
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([ADR 0141](../../02-DECISIONS/0141-the-host-delivers-its-own-successor.md)): every new version
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is the same resource with a new target. Since mesh-host 63 the record keeps a resource's former
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target so the next apply removes what the host wrote under it
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([issue 097](../097-a-resource-that-changes-target-leaves-the-old-one-behind/00-report.md)). So
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the new host's first apply found the previous version's directory as a former target of its own
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archive, and asked the removal for an archive — which does not exist
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([issue 162](../162-an-archive-cannot-be-undeclared/00-report.md)):
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```
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applying "mesh-host.next@former:/usr/lib/nox-mesh-host/versions/3c906749ad27": no way to remove a "archive"
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0 resource(s) were applied and remain
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```
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Orphans are removed before any resource is applied on a converged machine, so the refusal ended
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every apply at its first step. Every machine reported `failed`, applied nothing, and would have
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gone on doing so: a host fix is itself an archive the same apply would have to write, and the apply
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never reached it. The machines kept running what they had; nothing new from the mesh could land.
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## Why it matters beyond this instance
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Two rules that are each right met in the one resource the host cannot afford to stop on. Rule 5
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says a former target is removed and said; issue 162 says an archive has no removal, deliberately,
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so an unassignment nothing can undo is never reported as done. Neither rule was wrong; their
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meeting was never tested, because the bed that would have found it is a host replacing itself
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under the new rule, and the first such replacement was the live one. The fix is narrow: a former
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target of a kind the host cannot remove is left in place, said, and forgotten — never fatal,
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because nobody dropped it. An archive the declaration dropped still refuses, as 162 has it.
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## What it took to recover
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The broken host cannot apply its own fix: the fix is delivered as an archive, and the apply fails
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before writing anything. On each machine the host's record (`/var/lib/mesh-host/state.json`) had to
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lose the one `@former:` entry by hand, once, so that the next push could write the fixed archive and
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stand aside for it. A manual edit of the host's record is otherwise never done; it is written here
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because the alternative was four machines that could apply nothing.
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## Open questions
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- Should `Record` keep a former target for a kind the host cannot remove at all? The trace is
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useful; the removal it implies is not. Keeping it and letting the apply forget it is what the fix
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does; not recording it would be quieter.
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- Should the host's own versions directory be cleaned by the launcher rather than by the apply —
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the one archive whose former targets are genuinely removable, by the thing that knows which one
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runs?
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- Is there a bed that replaces a host under the current rules before the live mesh does
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(the proof row of [ADR 0141](../../02-DECISIONS/0141-the-host-delivers-its-own-successor.md) was
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a single crossover, before former targets existed)?
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