Refactor SendOfflineMessage to publish to push nodes first.

The code currently publishes to the DHT first and then to the pushnodes
when it finishes. This creates an opportunity where the node may be killed
while it's publishing to the DHT and before it has an opportunity to publish
to the pushnodes. This commit changes it to publish to the pushnodes in parrallel
to the DHT so as to avoid the potentional problem from above.

Author: cpacia

core/net.go

@@ -98,23 +98,32 @@ func (n *OpenBazaarNode) SendOfflineMessage(p peer.ID, k *libp2p.PubKey, m *pb.M
 		}
 	}
 	log.Debugf("Sending offline message to: %s, Message Type: %s, PointerID: %s, Location: %s", p.Pretty(), m.MessageType.String(), pointer.Cid.String(), pointer.Value.Addrs[0].String())
-	OfflineMessageWaitGroup.Add(2)
-	go func() {
-		ctx, cancel := context.WithCancel(context.Background())
-		defer cancel()
-		err := ipfs.PublishPointer(n.DHT, ctx, pointer)
-		if err != nil {
-			log.Error(err)
-		}
 
-		// Push provider to our push nodes for redundancy
-		for _, p := range n.PushNodes {
+	// We publish our pointers to three different locations:
+	// 1. The pushnodes
+	// 2. The DHT
+	// 3. Pubsub
+	// Each one is done in a separate goroutine so as to not block but we
+	// do increment the OfflineMessageWaitGroup which is used to block
+	// shutdown until all publishing is finished.
+	OfflineMessageWaitGroup.Add(2 + len(n.PushNodes))
+	for _, p := range n.PushNodes {
+		go func(pid peer.ID) {
 			ctx, cancel := context.WithCancel(context.Background())
 			defer cancel()
-			err := ipfs.PutPointerToPeer(n.DHT, ctx, p, pointer)
+			err := ipfs.PutPointerToPeer(n.DHT, ctx, pid, pointer)
 			if err != nil {
 				log.Error(err)
 			}
+			OfflineMessageWaitGroup.Done()
+		}(p)
+	}
+	go func() {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		err := ipfs.PublishPointer(n.DHT, ctx, pointer)
+		if err != nil {
+			log.Error(err)
 		}
 
 		OfflineMessageWaitGroup.Done()