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

@@ -33,19 +33,14 @@ import (
 // ability to change things, not the services its modules are serving — measured on 2026-09-27, when
 // a seat emptied mid-change and the control plane looped for two hours while every service stayed up.
 
-const rolloutUsage = "rollout check | rollout mint [--again] | rollout --confirm"
+const rolloutUsage = "rollout check | rollout mint | rollout --confirm"
 
 func rolloutCommand(ctx context.Context, args []string) error {
 	switch {
 	case len(args) == 1 && args[0] == "check":
 		return rolloutCheck(ctx)
 	case len(args) == 1 && args[0] == "mint":
-		return rolloutMint(ctx, false)
-	case len(args) == 2 && args[0] == "mint" && args[1] == "--again":
-		// Every credential minted afresh, whether or not one exists — for a mint that was wrong
-		// before anything was pushed. Afterwards nothing that received the old one still works,
-		// which is fine exactly when nothing received it.
-		return rolloutMint(ctx, true)
+		return rolloutMint(ctx)
 	case len(args) == 1 && args[0] == "--confirm":
 		return errors.New(
 			"the rollout itself is not built yet: `rollout check` answers whether it could run, and " +
@@ -210,7 +205,7 @@ func notReadyOf(state broker.Readiness) []string { return broker.NotReady(state)
 // why `rollout check` refuses until this has run. The bus's address is worked out here, from where
 // the module that provides it is assigned, rather than read from this process's environment: this
 // process is still on the old bus when this runs, and must be.
-func rolloutMint(ctx context.Context, again bool) error {
+func rolloutMint(ctx context.Context) error {
 	open, err := openStores(ctx)
 	if err != nil {
 		return err
@@ -248,33 +243,11 @@ func rolloutMint(ctx context.Context, again bool) 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.
-		// The host alone: no scheme (BareAddress adds one where none was, which is the wrong
-		// direction here — every URL built below adds its own) and no port.
-		_, _, host := broker.CredentialIn(known.Address)
-		if host == "" {
-			host = known.Address
-		}
-		if _, after, hasScheme := strings.Cut(host, "://"); hasScheme {
-			host = after
-		}
-		host = strings.TrimSpace(host)
-		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 {
@@ -300,7 +273,7 @@ func rolloutMint(ctx context.Context, again bool) error {
 
 	var machines, modules, skipped int
 	for _, p := range users {
-		if !again && !wanted[p.Username()] {
+		if !wanted[p.Username()] {
 			continue
 		}
 		switch p.Kind {

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",