Merge pull request 'Issue only the recorded holder a seat held once for the mesh (hq issue 218)' (#248) from fix/issue-218-only-the-holder-serves-a-mesh-seat into main

internal/inventory/busrecords.go

@@ -49,6 +49,12 @@ func (i *Inventory) BusRecords(ctx context.Context) (broker.Records, error) {
 		}
 	}
 
+	// Who holds each seat held once for the mesh, where the mesh recorded it (novox/hq issue 218).
+	holdings, err := i.Holdings(ctx)
+	if err != nil {
+		return broker.Records{}, fmt.Errorf("cannot read who holds the mesh's seats: %w", err)
+	}
+
 	out := broker.Records{Assigned: map[string][]broker.Declared{}, People: map[string][]string{},
 		Interchangeable: map[string]bool{}}
 	for _, n := range nodes {
@@ -72,7 +78,9 @@ func (i *Inventory) BusRecords(ctx context.Context) (broker.Records, error) {
 					"%s is assigned to %s and is not in the catalogue, so what it may say cannot "+
 						"be derived", module, n.Name)
 			}
-			out.Assigned[n.Name] = append(out.Assigned[n.Name], declaredFor(m, seats))
+			d := declaredFor(m, seats)
+			d.Holds = heldHere(d.Holds, holdings, n.Name, module)
+			out.Assigned[n.Name] = append(out.Assigned[n.Name], d)
 			if m.Instances == catalogue.InstancesInterchangeable {
 				out.Interchangeable[m.Module] = true
 			}
@@ -183,3 +191,33 @@ func (i *Inventory) NodesWithALiveToken(ctx context.Context) ([]string, error) {
 	}
 	return out, rows.Err()
 }
+
+// heldHere keeps of what a module claims only the seats it holds on this machine (novox/hq issue 218).
+// A seat held once per machine is held by every assignment that claims it. A seat held once for the
+// mesh is held by one assignment: where the mesh recorded who holds it, a claim on any other machine
+// grants nothing and issues nothing — or the module would serve the role's verbs from a machine that
+// is not the role's, and a question to the mesh's store would be answered from the wrong database. A
+// mesh seat with no holder on record is left as it was derived.
+func heldHere(claimed []broker.Seat, holdings []catalogue.Held, node, module string) []broker.Seat {
+	recorded := map[string][]catalogue.Held{}
+	for _, h := range holdings {
+		if h.Scope == catalogue.ScopeMesh {
+			recorded[h.Claim] = append(recorded[h.Claim], h)
+		}
+	}
+	var out []broker.Seat
+	for _, s := range claimed {
+		holders, onRecord := recorded[s.Name]
+		if s.Scope != catalogue.ScopeMesh || !onRecord {
+			out = append(out, s)
+			continue
+		}
+		for _, h := range holders {
+			if h.Node == node && h.Module == module {
+				out = append(out, s)
+				break
+			}
+		}
+	}
+	return out
+}

internal/inventory/heldhere_test.go

@@ -0,0 +1,32 @@
+package inventory
+
+import (
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/catalogue"
+)
+
+// novox/hq issue 218: a seat held once for the mesh is granted and issued only to the holder on record;
+// a node seat to every machine's claimant; a mesh seat with no holder on record as derived.
+func TestOnlyTheRecordedHolderHoldsAMeshSeat(t *testing.T) {
+	claimed := []broker.Seat{
+		{Name: "mesh-store", Scope: catalogue.ScopeMesh},
+		{Name: "node-packet-filter", Scope: catalogue.ScopeNode},
+		{Name: "unrecorded", Scope: catalogue.ScopeMesh},
+	}
+	holdings := []catalogue.Held{{Claim: "mesh-store", Scope: catalogue.ScopeMesh, Node: "control", Module: "postgres"}}
+	names := func(ss []broker.Seat) (out []string) {
+		for _, s := range ss {
+			out = append(out, s.Name)
+		}
+		return
+	}
+	if got := names(heldHere(claimed, holdings, "control", "postgres")); len(got) != 3 {
+		t.Errorf("the holder lost a seat: %v", got)
+	}
+	got := names(heldHere(claimed, holdings, "other", "postgres"))
+	if len(got) != 2 || got[0] != "node-packet-filter" || got[1] != "unrecorded" {
+		t.Errorf("a claimant on another machine holds %v; want the node seat and the unrecorded one, not the store", got)
+	}
+}