The control plane speaks the new bus

One environment variable moves it (design 25): MESH_BUS_NATS, read from the `bus`
secret `rollout mint` sealed to its machine, and the two that named the old bus go,
because being told about both is refused at start. Registered and built ahead of
the push that flips it, so the flip and the bus it flips to arrive in one
declaration — the same push that starts the new bus and hands this machine its
membership. Deliberately not merged until every credential is minted.

cmd/mesh-controller/rollout.go

@@ -243,24 +243,11 @@ func rolloutMint(ctx context.Context) error {
 	if err != nil {
 		return err
 	}
-	busHost := onNetwork[busNode]
-	if busHost == "" {
-		// **The hub is not in that map.** The machine that took over the tunnel is where the current
-		// bus already answers, and every machine dials it at the address the mesh handed them — so
-		// when the new bus runs on the same machine, that address is the one to tell them, with the
-		// new port. Found live: the control node is the hub, and the map lists the machines placed
-		// around it.
-		host := strings.TrimSpace(broker.BareAddress(known.Address))
-		if i := strings.LastIndex(host, ":"); i > 0 && !strings.Contains(host[i:], "]") {
-			host = host[:i]
-		}
-		if host == "" {
-			return fmt.Errorf("%s runs the new bus and has no address on the private network, and the "+
-				"current bus's address is unknown too, so no machine could be told where it is", busNode)
-		}
-		busHost = host
+	if onNetwork[busNode] == "" {
+		return fmt.Errorf("%s runs the new bus and has no address on the private network, so no machine "+
+			"could be told where it is", busNode)
 	}
-	busAddress := busHost + ":4222"
+	busAddress := onNetwork[busNode] + ":4222"
 
 	records, err := inv.BusRecords(ctx)
 	if err != nil {

module.json

@@ -47,15 +47,14 @@
         "MESH_STORE_INVENTORY_FILE": "/run/secrets/inventory",
         "MESH_STORE_IDENTITY_FILE": "/run/secrets/identity",
         "MESH_STORE_LICENCES_FILE": "/run/secrets/licences",
-        "MESH_BROKER_AMQP_FILE": "/run/secrets/broker",
         "MESH_BROKER_MANAGEMENT_FILE": "/run/secrets/broker-management",
         "MESH_BROKER_ADDRESS_FILE": "/run/secrets/broker-address",
         "MESH_STORE_INVENTORY_PORT": "${seat:mesh-store:5432}",
         "MESH_STORE_IDENTITY_PORT": "${seat:mesh-store:5432}",
         "MESH_STORE_LICENCES_PORT": "${seat:mesh-store:5432}",
-        "MESH_BROKER_AMQP_PORT": "${seat:mesh-broker:5672}",
         "MESH_BROKER_MANAGEMENT_PORT": "${seat:mesh-broker:15672}",
-        "MESH_BROKER_ADDRESS_PORT": "${seat:mesh-broker:5671}"
+        "MESH_BROKER_ADDRESS_PORT": "${seat:mesh-broker:5671}",
+        "MESH_BUS_NATS_FILE": "/run/secrets/bus"
       },
       "volumes": [
         "/var/lib/mesh-broker-tls:/broker-tls:ro",