Moves disable checks down into the sort routine.

consul/catalog_endpoint.go

@@ -105,12 +105,10 @@ func (c *Catalog) ListDatacenters(args *struct{}, reply *[]string) error {
 		dcs = append(dcs, dc)
 	}
 
-	// Sort the DCs
+	// Sort the DCs by name first, then apply a stable sort by distance.
 	sort.Strings(dcs)
-	if !c.srv.config.DisableCoordinates {
-		if err := c.srv.sortDatacentersByDistance(dcs); err != nil {
-			return err
-		}
+	if err := c.srv.sortDatacentersByDistance(dcs); err != nil {
+		return err
 	}
 
 	// Return
@@ -137,9 +135,6 @@ func (c *Catalog) ListNodes(args *structs.DCSpecificRequest, reply *structs.Inde
 			}
 
 			reply.Index, reply.Nodes = index, nodes
-			if c.srv.config.DisableCoordinates {
-				return nil
-			}
 			return c.srv.sortNodesByDistanceFrom(args.Source, reply.Nodes)
 		})
 }
@@ -200,9 +195,6 @@ func (c *Catalog) ServiceNodes(args *structs.ServiceSpecificRequest, reply *stru
 			if err := c.srv.filterACL(args.Token, reply); err != nil {
 				return err
 			}
-			if c.srv.config.DisableCoordinates {
-				return nil
-			}
 			return c.srv.sortNodesByDistanceFrom(args.Source, reply.ServiceNodes)
 		})
 

consul/rtt.go

@@ -113,8 +113,15 @@ func (s *Server) newSorterByDistanceFrom(c *coordinate.Coordinate, subj interfac
 // sortNodesByDistanceFrom is used to sort results from our service catalog based
 // on the round trip time from the given source node. Nodes with missing coordinates
 // will get stable sorted at the end of the list.
-
+//
+// If coordinates are disabled this will be a no-op.
 func (s *Server) sortNodesByDistanceFrom(source structs.QuerySource, subj interface{}) error {
+	// Make it safe to call this without having to check if coordinates are
+	// disabled first.
+	if s.config.DisableCoordinates {
+		return nil
+	}
+
 	// We can't compare coordinates across DCs.
 	if source.Datacenter != s.config.Datacenter {
 		return nil
@@ -131,7 +138,7 @@ func (s *Server) sortNodesByDistanceFrom(source structs.QuerySource, subj interf
 		return nil
 	}
 
-	// Do the Dew!
+	// Do the sort!
 	sorter, err := s.newSorterByDistanceFrom(coord, subj)
 	if err != nil {
 		return err
@@ -182,7 +189,16 @@ func (s *serverSerfer) GetNodesForDatacenter(dc string) []string {
 // sortDatacentersByDistance will sort the given list of DCs based on the
 // median RTT to all nodes we know about from the WAN gossip pool). DCs with
 // missing coordinates will be stable sorted to the end of the list.
+//
+// If coordinates are disabled this will be a no-op.
 func (s *Server) sortDatacentersByDistance(dcs []string) error {
+	// Make it safe to call this without having to check if coordinates are
+	// disabled first.
+	if s.config.DisableCoordinates {
+		return nil
+	}
+
+	// Do the sort!
 	serfer := serverSerfer{s}
 	return sortDatacentersByDistance(&serfer, dcs)
 }