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A build is announced under both names on the old bus, or merging breaks the live mesh

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Found by asking what merging this would do to the mesh that is actually running — the
only place the question could have been asked, because the tests were green and both
buses were self-consistent.

Moving the build outcome to the role means a catalogue built from the current manifests
listens for the role's name. The catalogue *already running* listens for the module's,
because that is what it was told when it was installed. The two do not meet, so merging
as it stood would have stopped the live mesh's module graph being updated — silently,
since a binding that matches nothing is not an error.

A rename on a live bus needs the publisher and the subscriber to change together, and a
deployment cannot promise which arrives first. So the old bus announces under both names
and the order stops mattering. The module's own name retires with the bus, in step 5's
list; nothing has ever run on the bus being built, so there is no legacy name there and
this doubling has no counterpart.
This commit is contained in:
jschoubben
2026-09-27 17:39:39 +02:00
parent e5007a7daa
commit 5fcde512bc
3 changed files with 64 additions and 2 deletions
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internal/link/builds_current.go
+20 -2
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@@ -161,8 +161,26 @@ func (b *currentBuild) Announce(ctx context.Context, result BuildResult) error {
if result.Failed != "" || result.Commit == "" {
return nil
}
return EmitEvent(ctx, OverCurrent{Channel: b.channel}, KeyModuleBuilt, "builder", b.on,
announcementOf(result))
// **Announced under both names on this bus, for exactly as long as this bus lives.**
//
// A build's outcome belongs to the role now (novox/hq ADR 0121), so a catalogue built from the
// current manifests listens for the role's name. A catalogue that is *already running* listens for
// the module's, because that is what it was told when it was installed. A rename on a live bus
// needs the publisher and the subscriber to change together, and a merge cannot promise that: one
// of them is deployed first, and in that window the graph silently stops being updated — which is
// the failure this whole change was cleaning up after.
//
// So both, and the order stops mattering. The module's own name goes with the bus, in step 5's
// retirement list; nothing has ever run on the bus being built, so there is no legacy name there
// and this doubling has no counterpart.
announced := announcementOf(result)
if err := EmitEvent(ctx, OverCurrent{Channel: b.channel}, KeyModuleBuilt, "builder", b.on,
announced); err != nil {
return err
}
return EmitEvent(ctx, OverCurrent{Channel: b.channel}, KeyRoleBuilt, TheBuildMachine, b.on,
announced)
}
func (b *currentBuild) Done() error { return b.delivery.Ack(false) }