feat: initial scaffold of unibus message bus (membership service + client lib + demo peers)

pkg/embeddednats/embeddednats.go

@@ -0,0 +1,48 @@
+// Package embeddednats starts an in-process NATS server with JetStream enabled.
+//
+// This lets the whole unibus stack run with `go run` without installing or
+// managing a separate NATS deployment. In production, point clients at an
+// external NATS via the --nats-url flag instead of using this.
+package embeddednats
+
+import (
+	"fmt"
+	"time"
+
+	server "github.com/nats-io/nats-server/v2/server"
+)
+
+// Start launches an embedded nats-server with JetStream enabled, listening on
+// the given port and persisting JetStream state under storeDir. It blocks until
+// the server is ready to accept connections (up to 5s) and returns the running
+// server. The caller is responsible for calling Shutdown on it.
+func Start(storeDir string, port int) (*server.Server, error) {
+	opts := &server.Options{
+		JetStream:  true,
+		StoreDir:   storeDir,
+		Port:       port,
+		DontListen: false,
+		// Keep the embedded server quiet by default; the host app logs the URLs.
+		NoLog:  true,
+		NoSigs: true,
+	}
+
+	ns, err := server.NewServer(opts)
+	if err != nil {
+		return nil, fmt.Errorf("embeddednats: new server: %w", err)
+	}
+
+	go ns.Start()
+
+	if !ns.ReadyForConnections(5 * time.Second) {
+		ns.Shutdown()
+		return nil, fmt.Errorf("embeddednats: server not ready for connections within 5s")
+	}
+
+	return ns, nil
+}
+
+// ClientURL returns a NATS connection URL for the running embedded server.
+func ClientURL(ns *server.Server) string {
+	return ns.ClientURL()
+}