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Let the mesh's resolver seat have several holders on record

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musl takes the first reply from any listed nameserver, so a public fallback
beside the mesh's resolver answered NXDOMAIN for mesh names in every Alpine
container (hq ADR 0223). The fix is two mesh resolvers and no public one, which
needs mesh-dns-resolver held on two machines: a seat can now be replicated,
each holder recorded by 'seat <name> --add', checkClaims accepts every holder
on record and still refuses a second holder of any other mesh seat, a holder
answers its own requirement, and a roster fact gives each replicated seat's
holders, this machine first, so resolv-conf can list them. Migration 0062 keys
a holding by seat and assignment.
This commit is contained in:
jochen
2026-10-05 22:38:44 +02:00
parent 8a400d165e
commit 130d20114b
13 changed files with 556 additions and 66 deletions
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internal/catalogue/seats.go
+33 -15
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@@ -21,8 +21,16 @@ import (
type Seat struct {
// Name is what a manifest claims.
Name string
// Scope is where there may be only one holder.
// Scope is where there may be only one holder — unless the seat is Replicated.
Scope string
// Replicated says a mesh seat may be held on several machines at once, each holder answering the
// same thing (novox/hq ADR 0223): the mesh's resolver, held on the anchor and the home server so a
// machine's resolver file lists two that give one answer. Each holder is on record, added by an
// act (`seat <name> --add <node>/<module>`), never by being assigned: two claimants with nothing on
// record are refused exactly as for any mesh seat. One per machine still — two modules on one
// node claiming it are refused. Compiled, never stored, like Needs: it is the mesh's definition of
// the role, and the store's rows carry no column for it.
Replicated bool
// Delivers is the provision the seat's holder answers for, or empty. A seat that delivers a
// provision may only be held by a module providing it at the seat's scope, and its holder is
// what a requirement for that provision resolves to when several modules provide it.
@@ -140,10 +148,14 @@ var defaultSeats = append([]Seat{
// that machine unresolvable in the meantime. Deleted once no registered manifest claims it.
{Name: "mesh-build-machine", Scope: ScopeMesh,
Accepts: []string{"build"}, Emits: []string{"started", "built", "log.*"}, Decision: "novox/hq ADR 0190"},
// **The mesh's one resolver** (novox/hq ADR 0194, 0196): every node's internal domain, held in one
// place, and every node and container asks it first. Delivers what a machine's resolver
// configuration requires, so that requirement resolves to the holder wherever it is placed.
{Name: "mesh-dns-resolver", Scope: ScopeMesh, Delivers: "wildcard-resolution", Decision: "novox/hq ADR 0194"},
// **The mesh's resolvers** (novox/hq ADR 0194, 0196, 0223): every node's internal domain, and
// every node and container asks them and nothing else. Replicated since ADR 0223: held on more
// than one machine, each answering the same names from the same roster, and every machine's
// resolver file lists every holder — its own first — and no public resolver, so whichever answers
// first gives the one answer. Delivers what a machine's resolver configuration requires, so that
// requirement resolves to a holder wherever they are placed.
{Name: "mesh-dns-resolver", Scope: ScopeMesh, Delivers: "wildcard-resolution", Replicated: true,
Decision: "novox/hq ADR 0194, ADR 0223"},
// **A machine's /etc/hosts is one module's** (novox/hq ADR 0199): its holder writes the machine's
// own lines and keeps every other line as the operator's, changed through these three verbs on that
// machine alone. The controller holds none of it.
@@ -314,11 +326,12 @@ func UseSeats(s []Seat) {
row.Accepts, row.Emits, row.Serves = d.Accepts, d.Emits, d.Serves
}
}
// What a seat receives and what its holder needs are never stored (novox/hq ADR 0212, ADR
// 0220), so they are always the compiled ones.
// What a seat receives, what its holder needs and whether it is replicated are never stored
// (novox/hq ADR 0212, ADR 0220, ADR 0223), so they are always the compiled ones.
if d, known := byName[row.Name]; known {
row.Receives = d.Receives
row.Needs = d.Needs
row.Replicated = d.Replicated
}
merged = append(merged, row)
}
@@ -498,19 +511,24 @@ func seatNames() string {
// two modules on one node could both provide a provision, and only the one holding the seat
// answers for it. Nothing when no seat delivers the provision, when nobody holds
// it, or when the holder is not among the providers offered.
//
// **The first holder in the providers' own order** (novox/hq ADR 0223). A replicated seat has
// several, and the answer must not depend on the order the mesh happened to resolve its machines
// in: the providers come sorted by machine, so every consumer is bound to the same one. A seat with
// one holder gets the same answer as before.
func HolderAmong(provision string, providers []Provider, held []Held) (Provider, bool) {
seat, delivered := SeatDelivering(provision)
if !delivered {
return Provider{}, false
}
for _, h := range held {
// Resolve the held claim to a seat rather than comparing names, so a record naming a seat's
// former name still matches it after a rename (novox/hq ADR 0122).
hs, ok := SeatNamed(h.Claim)
if !ok || hs.Name != seat.Name || h.Scope != seat.Scope {
continue
}
for _, p := range providers {
for _, p := range providers {
for _, h := range held {
// Resolve the held claim to a seat rather than comparing names, so a record naming a
// seat's former name still matches it after a rename (novox/hq ADR 0122).
hs, ok := SeatNamed(h.Claim)
if !ok || hs.Name != seat.Name || h.Scope != seat.Scope {
continue
}
if p.Node == h.Node && p.Module == h.Module {
return p, true
}