NewStream failure right after startup

[cpacia]

This took me forever debug, but here's the issue. If you start up two nodes and immediately join a topic they will fail discover each other in the pubsub. Here's why:

Node1

• Create host
• Create pubsub

Node2

• Create host
  • This causes an immediate connection to Node1 but the pubsub protocol is not yet registered.
  • Node1's pubsub detects the new connection, tries to open a stream, and NewStream fails because Node2 doesn't yet speak pubsub.
• Create pubsub
  • Node2's pubsub doesn't detect the connection since it was established before the pubsub was created.

Nodes 1 and 2 never connect :(

Fortunately I was able to come up with a fix that doesn't require any changes in libp2p. Basically detect the protocolupdate event and force it think it received a new connection:

        protocolUpdatedSub, err := host.EventBus().Subscribe(new(event.EvtPeerProtocolsUpdated))
	if err != nil {
		return nil, err
	}
	go func(sub event.Subscription) {
		for {
			select {
			case evt, ok := <-sub.Out():
				if !ok {
					return
				}
				var updated bool
				for _, proto := range evt.(event.EvtPeerProtocolsUpdated).Added {
					if proto == cfg.params.ProtocolPrefix+pubsub.GossipSubID_v11 {
						updated = true
						break
					}
				}
				if updated {
					for _, c := range host.Network().ConnsToPeer(evt.(event.EvtPeerProtocolsUpdated).Peer) {
						(*pubsub.PubSubNotif)(ps).Connected(host.Network(), c)
					}
				}
			}
		}
	}(protocolUpdatedSub)

But it would be nice if this was built in as it's definitely not expected behavior.

[cpacia]

Looks like there is an open PR attempting to address this issue.