Consume ring buffer for networks added on-the-fly

downstream.go

@@ -702,11 +702,27 @@ func (dc *downstreamConn) register() error {
 	})
 
 	dc.forEachNetwork(func(net *network) {
+		// TODO: need to take dc.network into account when deciding whether or
+		// not to load history
+		dc.runNetwork(net, firstDownstream)
+	})
+
+	return nil
+}
+
+// runNetwork starts listening for messages coming from the network's ring
+// buffer.
+//
+// It panics if the network is not suitable for the downstream connection.
+func (dc *downstreamConn) runNetwork(net *network, loadHistory bool) {
+	if dc.network != nil && net != dc.network {
+		panic("network not suitable for downstream connection")
+	}
+
 	historyName := dc.rawUsername
 
-		// TODO: need to take dc.network into account here
 	var seqPtr *uint64
-		if firstDownstream {
+	if loadHistory {
 		net.lock.Lock()
 		seq, ok := net.history[historyName]
 		net.lock.Unlock()
@@ -715,7 +731,6 @@ func (dc *downstreamConn) register() error {
 		}
 	}
 
-		// TODO: we need to create a consumer when adding networks on-the-fly
 	consumer, ch := net.ring.NewConsumer(seqPtr)
 	go func() {
 		for {
@@ -749,9 +764,6 @@ func (dc *downstreamConn) register() error {
 			net.lock.Unlock()
 		}
 	}()
-	})
-
-	return nil
 }
 
 func (dc *downstreamConn) runUntilRegistered() error {

user.go

@@ -198,14 +198,26 @@ func (u *user) removeDownstream(dc *downstreamConn) {
 }
 
 func (u *user) createNetwork(net *Network) (*network, error) {
+	if net.ID != 0 {
+		panic("tried creating an already-existing network")
+	}
+
 	network := newNetwork(u, net)
 	err := u.srv.db.StoreNetwork(u.Username, &network.Network)
 	if err != nil {
 		return nil, err
 	}
+
+	u.forEachDownstream(func(dc *downstreamConn) {
+		if dc.network == nil {
+			dc.runNetwork(network, false)
+		}
+	})
+
 	u.lock.Lock()
 	u.networks = append(u.networks, network)
 	u.lock.Unlock()
+
 	go network.run()
 	return network, nil
 }