initialize tracer with peer ID, trace RPC from join/leave announcements

pubsub.go

@@ -326,7 +326,7 @@ func WithDiscovery(d discovery.Discovery, opts ...DiscoverOpt) Option {
 // WithEventTracer provides a tracer for the pubsub system
 func WithEventTracer(tracer EventTracer) Option {
 	return func(p *PubSub) error {
-		p.tracer = &pubsubTracer{tracer: tracer}
+		p.tracer = &pubsubTracer{tracer: tracer, pid: p.host.ID()}
 		return nil
 	}
 }
@@ -582,8 +582,10 @@ func (p *PubSub) announce(topic string, sub bool) {
 	for pid, peer := range p.peers {
 		select {
 		case peer <- out:
+			p.tracer.SendRPC(out, pid)
 		default:
 			log.Infof("Can't send announce message to peer %s: queue full; scheduling retry", pid)
+			p.tracer.DropRPC(out, pid)
 			go p.announceRetry(pid, topic, sub)
 		}
 	}
@@ -619,8 +621,10 @@ func (p *PubSub) doAnnounceRetry(pid peer.ID, topic string, sub bool) {
 	out := rpcWithSubs(subopt)
 	select {
 	case peer <- out:
+		p.tracer.SendRPC(out, pid)
 	default:
 		log.Infof("Can't send announce message to peer %s: queue full; scheduling retry", pid)
+		p.tracer.DropRPC(out, pid)
 		go p.announceRetry(pid, topic, sub)
 	}
 }

trace.go

@@ -12,6 +12,7 @@ type EventTracer interface {
 
 type pubsubTracer struct {
 	tracer EventTracer
+	pid    peer.ID
 }
 
 func (t *pubsubTracer) PublishMessage(msg *Message) {