One bus: the AMQP transport is gone from the controller

The mesh runs on the seat's bus alone (novox/hq ADR 0131, design 28 task 5.5). The old
transport's consume loop, build request, tool ask, management API and account scoping are
deleted, and the bus switch with them; the controller connects to the broker seat and to
nothing else. The store-window tests keep their assertions on a bus-less fake, and the tests
that only made sense for the old transport's in-memory holding go with it.

internal/link/serve.go

@@ -11,10 +11,6 @@ import (
 	"log"
 	"os"
 	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-
-	"github.com/novox/mesh-controller/internal/envfile"
 )
 
 // AMQPVar is the controller's own connection to the bus the mesh runs on today.
@@ -71,8 +67,6 @@ type Upgrader interface {
 type Server struct {
 	inbound Inbound
 	bus     Bus
-	conn    *amqp.Connection
-	channel *amqp.Channel
 	js      *broker.JetStream
 
 	enroller Enroller
@@ -127,85 +121,18 @@ func (s *Server) Answers(r Replayer) error {
 // On the port MESH_BROKER_AMQP_PORT names when the node's settings moved the broker (novox/hq
 // 04-ISSUES/102) — the URL is genesis's, sealed, and its port is the one thing in it the node may
 // have moved since.
-func Connect(enroller Enroller, listener Listener) (*Server, error) {
-	url, err := envfile.Placed(AMQPVar)
-	if err != nil {
-		return nil, err
-	}
-	if url == "" {
-		return nil, fmt.Errorf(
-			"this control plane has no %s, so it cannot reach its broker. Nodes talk to it over "+
-				"the broker and nowhere else, so without this it can hold records and answer "+
-				"nothing", AMQPVar)
-	}
-
-	conn, err := amqp.Dial(url)
-	if err != nil {
-		// Not quoted back: the URL carries the controller's own bus password.
-		return nil, fmt.Errorf("cannot reach the broker named in %s: %w", AMQPVar, err)
-	}
-	channel, err := conn.Channel()
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-
-	// Declared here rather than assumed. The controller is the only thing that may create them — a
-	// node's account can write to this exchange and read its own queue, and configure nothing
-	// else, so a node arriving before the controller has ever run finds nothing and says so,
-	// rather than quietly creating a topology nobody designed.
-	if err := channel.ExchangeDeclare(Exchange, "direct", true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s exchange: %w", Exchange, err)
-	}
-	// The events exchange too. The controller is not the only publisher on it — modules announce
-	// onto it with their own accounts — but it is the only thing permitted to create it, for the
-	// same reason it is the only thing permitted to create the direct one.
-	if err := channel.ExchangeDeclare(EventsExchange, "topic", true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s exchange: %w", EventsExchange, err)
-	}
-	if _, err := channel.QueueDeclare(ControlQueue, true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s queue: %w", ControlQueue, err)
-	}
-	// Every key a node may publish. Binding one and forgetting another is a message the bus
-	// accepts, finds no queue for, and drops — the publisher sees success and the consumer sees
-	// nothing. That is exactly what happened to reports: `report` was left unbound while `enrol`
-	// worked, so nodes announced what they had applied into a void for an afternoon.
-	for _, key := range []string{KeyEnrol, KeyReport, KeyAlive, KeyBuilt} {
-		if err := channel.QueueBind(ControlQueue, key, Exchange, false, nil); err != nil {
-			conn.Close()
-			return nil, fmt.Errorf("cannot bind %s to %s/%s: %w", ControlQueue, Exchange, key, err)
-		}
-	}
-
-	return &Server{
-		inbound:  Current(conn, channel),
-		bus:      OverCurrent{Channel: channel},
-		conn:     conn,
-		channel:  channel,
-		enroller: enroller,
-		listener: listener,
-		log:      newLog(),
-	}, nil
+// Connect is ConnectNats: the mesh has one bus (novox/hq ADR 0131, design 28 task 5.5). Kept as
+// the name callers know; the transport it opened before is gone with the bus it spoke to.
+func Connect(js *broker.JetStream, enroller Enroller, listener Listener) *Server {
+	return ConnectNats(js, enroller, listener)
 }
 
 func newLog() *log.Logger { return log.New(os.Stdout, "", log.LstdFlags) }
 
-// Channel is the controller's channel, for the command line's own publishing.
-func (s *Server) Channel() *amqp.Channel { return s.channel }
-
 func (s *Server) Close() {
 	if s.inbound != nil {
 		s.inbound.Close()
 	}
-	if s.channel != nil {
-		_ = s.channel.Close()
-	}
-	if s.conn != nil {
-		_ = s.conn.Close()
-	}
 	if s.js != nil {
 		s.js.Close()
 	}
@@ -349,7 +276,6 @@ func (s *Server) reported(ctx context.Context, m Control) {
 		_ = m.Drop()
 		return
 	}
-	m.About("report " + report.Node)
 	what := fmt.Sprintf("%s's report of declaration %s", report.Node, report.Declared)
 
 	if s.listener != nil {
@@ -482,9 +408,6 @@ func (s *Server) wasBuilt(ctx context.Context, m Control) {
 		_ = m.Drop()
 		return
 	}
-	// Each build result its own subject: none supersedes another, and recording one twice is
-	// harmless — the build is kept by its id.
-	m.About("build " + digest(m.Body()))
 	err := s.recorder.Built(ctx, result)
 	switch s.decide(ctx, m, fmt.Sprintf("a build result from %s", result.On), "", "", err) {
 	case Hold:
@@ -516,7 +439,6 @@ func (s *Server) wasBuilt(ctx context.Context, m Control) {
 // the catalogue next restarts (issue 083). One request stands for all: a newer one supersedes one
 // still held.
 func (s *Server) catchingUp(ctx context.Context, m Control) {
-	m.About("catch-up")
 	if s.replayer == nil {
 		s.log.Printf("a catalogue asked to catch up and this control plane has nothing to replay")
 		_ = m.Took()
@@ -569,7 +491,6 @@ func (s *Server) moved(ctx context.Context, m Control) {
 		_ = m.Took()
 		return
 	}
-	m.About("upgrade " + u.Module)
 	if u.Module == "" {
 		s.log.Printf("an upgrade announcement named no module; ignored")
 		_ = m.Took()
@@ -620,7 +541,6 @@ func (s *Server) sourceMoved(ctx context.Context, m Control) {
 		_ = m.Took()
 		return
 	}
-	m.About("merge " + moved.Owner + "/" + moved.Repo + " into " + moved.Base)
 	if moved.Commit == "" || moved.Repo == "" {
 		s.log.Printf("a merge announcement named no repository or no commit; ignored")
 		_ = m.Took()