rpc: query the database instead of active peers for the ListChannel RPC

This commit takes advantage of the newly added
channeldb.FetchAllChannels method to return the state of all active
channels for the ListChannels RPC command. With this change the state
of all channels can now be queried regardless of if any/all the peers
are currently online.

In a future modification a bit will be added to the channel information
which indicates if the LinkNode the channel was created with is
currently online or not.

peer.go

@@ -590,6 +590,11 @@ out:
 			req.resp <- snapshots
 
 		case pendingChanPoint := <-p.barrierInits:
+			// A new channel has almost finished the funding
+			// process. In order to properly synchronize with the
+			// writeHandler goroutine, we add a new channel to the
+			// barriers map which will be closed once the channel
+			// is fully open.
 			p.barrierMtx.Lock()
 			peerLog.Tracef("Creating chan barrier for "+
 				"ChannelPoint(%v)", pendingChanPoint)

rpcserver.go

@@ -454,41 +454,45 @@ func (r *rpcServer) PendingChannels(ctx context.Context,
 
 // ListChannels returns a description of all direct active, open channels the
 // node knows of.
-// TODO(roasbeef): read all active channels from the DB?
-//   * add 'online' toggle bit
+// TODO(roasbeef): add 'online' bit to response
 func (r *rpcServer) ListChannels(ctx context.Context,
 	in *lnrpc.ListChannelsRequest) (*lnrpc.ListChannelsResponse, error) {
 
 	resp := &lnrpc.ListChannelsResponse{}
-	peers := r.server.Peers()
 
-	for _, peer := range peers {
-		lnID := hex.EncodeToString(peer.identityPub.SerializeCompressed())
-		chanSnapshots := peer.ChannelSnapshots()
+	dbChannels, err := r.server.chanDB.FetchAllChannels()
+	if err != nil {
+		return nil, err
+	}
 
-		for _, chanSnapshot := range chanSnapshots {
-			channel := &lnrpc.ActiveChannel{
-				RemotePubkey:  lnID,
-				ChannelPoint:  chanSnapshot.ChannelPoint.String(),
-				Capacity:      int64(chanSnapshot.Capacity),
-				LocalBalance:  int64(chanSnapshot.LocalBalance),
-				RemoteBalance: int64(chanSnapshot.RemoteBalance),
-				NumUpdates:    chanSnapshot.NumUpdates,
-				PendingHtlcs:  make([]*lnrpc.HTLC, len(chanSnapshot.Htlcs)),
-			}
-			for i, htlc := range chanSnapshot.Htlcs {
-				channel.PendingHtlcs[i] = &lnrpc.HTLC{
-					Incoming:         htlc.Incoming,
-					Amount:           int64(htlc.Amt),
-					HashLock:         htlc.RHash[:],
-					ExpirationHeight: htlc.RefundTimeout,
-					RevocationDelay:  htlc.RevocationDelay,
-				}
-			}
+	rpcsLog.Infof("[listchannels] fetched %v channels from DB",
+		len(dbChannels))
 
-			resp.Channels = append(resp.Channels, channel)
+	for _, dbChannel := range dbChannels {
+		nodePub := dbChannel.IdentityPub.SerializeCompressed()
+		nodeID := hex.EncodeToString(nodePub)
+
+		channel := &lnrpc.ActiveChannel{
+			RemotePubkey:  nodeID,
+			ChannelPoint:  dbChannel.ChanID.String(),
+			Capacity:      int64(dbChannel.Capacity),
+			LocalBalance:  int64(dbChannel.OurBalance),
+			RemoteBalance: int64(dbChannel.TheirBalance),
+			NumUpdates:    dbChannel.NumUpdates,
+			PendingHtlcs:  make([]*lnrpc.HTLC, len(dbChannel.Htlcs)),
 		}
 
+		for i, htlc := range dbChannel.Htlcs {
+			channel.PendingHtlcs[i] = &lnrpc.HTLC{
+				Incoming:         htlc.Incoming,
+				Amount:           int64(htlc.Amt),
+				HashLock:         htlc.RHash[:],
+				ExpirationHeight: htlc.RefundTimeout,
+				RevocationDelay:  htlc.RevocationDelay,
+			}
+		}
+
+		resp.Channels = append(resp.Channels, channel)
 	}
 
 	return resp, nil