Serve the read verbs on the serving controller's own connection, and name every connection

Each verb ran as a process that dialled the bus, so hundreds of short
connections an hour, all named mesh-controller, hid any client reconnecting
in a loop (hq issue 327). D15 now says a user whose connections keep dropping.

cmd/mesh-controller/replay327_test.go

@@ -0,0 +1,132 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/nats-io/nats-server/v2/server"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/testbus"
+)
+
+// novox/hq issue 327, replayed with only what the controller had before its fix, so it can be laid over
+// the older commit. On 2026-10-08 the bus's connection total rose by 5.2 a minute while the same 16
+// connections stayed open, and three calls of `conditions` in one second added three: each verb ran as a
+// process of the controller's own binary, which dialled the bus, logged in and left. The operator's
+// channel reads `conditions` at least once a minute. A verb that only reads, served by the serving
+// controller, opens no connection of its own.
+func TestReplay327(t *testing.T) {
+	bus := testbus.Start(t)
+	serving, err := broker.Dial(bus.ClientURL())
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer serving.Close()
+	if err := serving.EnsureControllerBuckets(); err != nil {
+		t.Fatal(err)
+	}
+	keeper, err := keeperOn(context.Background(), serving.Conn())
+	if err != nil {
+		t.Fatal(err)
+	}
+	// The serving controller: its keeper and its connection, as serve sets them.
+	keptBefore, connBefore := conditionsFrom, handActConn
+	conditionsFrom, handActConn = keeper, serving.Conn()
+	defer func() { conditionsFrom, handActConn = keptBefore, connBefore }()
+	// A verb that runs as a process of its own runs this controller's binary, on this bus.
+	asAProcess(t, bus.ClientURL())
+
+	handlers, _, err := seatToolHandlers()
+	if err != nil {
+		t.Fatal(err)
+	}
+	accepted := func() uint64 {
+		v, err := bus.Varz(nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return v.TotalConnections
+	}
+	before := accepted()
+	for i := 0; i < 3; i++ {
+		answer, err := handlers["conditions"](context.Background(), json.RawMessage(`{}`))
+		if err != nil {
+			t.Fatal(err)
+		}
+		if a, ok := answer.(verbAnswer); !ok || !a.OK {
+			t.Fatalf("conditions answered %+v", answer)
+		}
+	}
+	if opened := accepted() - before; opened != 0 {
+		t.Fatalf("three conditions calls opened %d connection(s) to the bus; the serving controller is on it already",
+			opened)
+	}
+}
+
+// The binary a verb run as a process of its own is, built once for the tests that run one.
+var verbBinary struct {
+	once sync.Once
+	path string
+	err  error
+}
+
+// asAProcess makes a verb that runs as a process of its own run this package's binary, on the bus at url.
+func asAProcess(t *testing.T, url string) {
+	t.Helper()
+	verbBinary.once.Do(func() {
+		dir, err := os.MkdirTemp("", "mesh-controller-verb-")
+		if err != nil {
+			verbBinary.err = err
+			return
+		}
+		verbBinary.path = filepath.Join(dir, "mesh-controller")
+		out, err := exec.Command("go", "build", "-o", verbBinary.path, ".").CombinedOutput()
+		if err != nil {
+			verbBinary.err = &buildError{out: string(out), err: err}
+		}
+	})
+	if verbBinary.err != nil {
+		t.Fatalf("the controller could not be built to run a verb as its own process: %v", verbBinary.err)
+	}
+	was := ownImage
+	ownImage = func() string { return verbBinary.path }
+	t.Cleanup(func() { ownImage = was })
+	t.Setenv(broker.NATSVar, url)
+	t.Setenv(broker.CertificateVar, "")
+}
+
+type buildError struct {
+	out string
+	err error
+}
+
+func (e *buildError) Error() string { return e.err.Error() + ": " + e.out }
+
+// closedNames are the names of the connections the bus saw closed.
+func closedNames(t *testing.T, bus *server.Server) []string {
+	t.Helper()
+	deadline := time.Now().Add(5 * time.Second)
+	var names []string
+	for time.Now().Before(deadline) {
+		connz, err := bus.Connz(&server.ConnzOptions{State: server.ConnClosed})
+		if err != nil {
+			t.Fatal(err)
+		}
+		names = names[:0]
+		for _, c := range connz.Conns {
+			names = append(names, c.Name)
+		}
+		if len(names) > 0 {
+			return names
+		}
+		time.Sleep(50 * time.Millisecond)
+	}
+	return names
+}