[daemon] Daemon BigBang event retrieval

During daemon startup we now buffer publications to allow event clients
to retrieve all published event. After 200ms the buffering is disabled.

Before this commit, during daemon startup we couldn't get the initial
events until the listener is started.

om node event re-connect time is reduced to 100ms to allow reconnect
before daemon event buffering is disabled.

core/omcmd/node_events.go

@@ -296,7 +296,9 @@ func (t *CmdNodeEvents) nodeEventLoop(ctx context.Context, nodename string) {
 				_, _ = fmt.Fprintf(os.Stderr, "event read failed for node %s: '%s'\n", nodename, err)
 				_, _ = fmt.Fprintln(os.Stderr, "press ctrl+c to interrupt retries")
 			}
-			time.Sleep(1 * time.Second)
+			// wait time before reconnect, it is short to avoid loosing daemon
+			// restart events.
+			time.Sleep(100 * time.Millisecond)
 			select {
 			case <-ctx.Done():
 				t.errC <- ctx.Err()

daemon/daemon/main.go

@@ -99,15 +99,27 @@ func (t *T) Start(ctx context.Context) error {
 	t.ctx = pubsub.ContextWithBus(t.ctx, bus)
 	t.wg.Add(1)
 	bus.Start(t.ctx)
+	bus.EnableBufferPublication(2000)
+	bus.Pub(&msgbus.DaemonStatusUpdated{Node: localhost, Version: version.Version(), Status: "starting"}, labelLocalhost)
+
 	t.bus = bus
 	t.stopFuncs = append(t.stopFuncs, func() error {
+		bus.Pub(&msgbus.DaemonStatusUpdated{Node: localhost, Version: version.Version(), Status: "stopped"}, labelLocalhost)
+		// give chance for DaemonStatusUpdated message to reach peers
+		time.Sleep(300 * time.Millisecond)
 		defer t.wg.Done()
 		t.log.Infof("stop pubsub bus")
 		t.bus.Stop()
 		t.log.Infof("stopped pubsub bus")
 		return nil
 	})
 
+	defer func() {
+		// give a chance for event client to reconnect to the daemon
+		time.Sleep(200 * time.Millisecond)
+		bus.DisableBufferPublication()
+	}()
+
 	defer t.stopWatcher()
 
 	go t.notifyWatchDogSys(t.ctx)
@@ -187,6 +199,9 @@ func (t *T) Stop() error {
 	var errs error
 	// stop goroutines without cancel context
 	t.logTransition("stopping 🟡")
+	localhost := hostname.Hostname()
+	t.bus.Pub(&msgbus.DaemonStatusUpdated{Node: localhost, Version: version.Version(), Status: "stopping"}, pubsub.Label{"node", localhost})
+	time.Sleep(300 * time.Millisecond)
 	defer t.logTransition("stopped 🟡")
 	for i := len(t.stopFuncs) - 1; i >= 0; i-- {
 		if err := t.stopFuncs[i](); err != nil {