show forward DNS name for internet addresses

...if available.

Follow-up to #1863.

render/detailed/connections.go

@@ -5,7 +5,6 @@ import (
 	"sort"
 	"strconv"
 
-	"github.com/weaveworks/scope/probe/endpoint"
 	"github.com/weaveworks/scope/render"
 	"github.com/weaveworks/scope/report"
 )
@@ -113,12 +112,10 @@ func internetAddr(node report.Node, ep report.Node) (string, bool) {
 	if !ok {
 		return "", false
 	}
-	if set, ok := ep.Sets.Lookup(endpoint.ReverseDNSNames); ok && len(set) > 0 {
-		// TODO We show just one of the names, selected rather
-		// abitrarily. We don't have space to show all (except in the
-		// tooltip perhaps), but should think of better strategies for
-		// choosing the name to display.
-		addr = fmt.Sprintf("%s (%s)", set[0], addr)
+	if names := render.DNSNames(ep); len(names) > 0 {
+		// we show the "most important" name only, since we don't have
+		// space for more
+		addr = fmt.Sprintf("%s (%s)", names[0], addr)
 	}
 	return addr, true
 }

render/process.go

@@ -158,24 +158,29 @@ func MapProcess2Name(n report.Node, _ report.Networks) report.Nodes {
 	return report.Nodes{name: node}
 }
 
-func externalNode(m report.Node) report.Node {
+func externalNode(n report.Node) report.Node {
 	// First, check if it's a known service and emit a
 	// a specific node if it is
-	snoopedHostnames, _ := m.Sets.Lookup(endpoint.SnoopedDNSNames)
-	reverseHostnames, _ := m.Sets.Lookup(endpoint.ReverseDNSNames)
-	// Sort the names to make the lookup more deterministic
-	sort.StringSlice(snoopedHostnames).Sort()
-	sort.StringSlice(reverseHostnames).Sort()
-	// Intentionally prioritize snooped hostnames
-	for _, hostname := range append(snoopedHostnames, reverseHostnames...) {
+	for _, hostname := range DNSNames(n) {
 		if isKnownService(hostname) {
-			return NewDerivedPseudoNode(ServiceNodeIDPrefix+hostname, m)
+			return NewDerivedPseudoNode(ServiceNodeIDPrefix+hostname, n)
 		}
 	}
 
 	// emit one internet node for incoming, one for outgoing
-	if len(m.Adjacency) > 0 {
-		return NewDerivedPseudoNode(IncomingInternetID, m)
+	if len(n.Adjacency) > 0 {
+		return NewDerivedPseudoNode(IncomingInternetID, n)
 	}
-	return NewDerivedPseudoNode(OutgoingInternetID, m)
+	return NewDerivedPseudoNode(OutgoingInternetID, n)
+}
+
+func DNSNames(n report.Node) []string {
+	snoopedNames, _ := n.Sets.Lookup(endpoint.SnoopedDNSNames)
+	reverseNames, _ := n.Sets.Lookup(endpoint.ReverseDNSNames)
+	// sort the names, to make selection for display more
+	// deterministic
+	sort.StringSlice(snoopedNames).Sort()
+	sort.StringSlice(reverseNames).Sort()
+	// prioritize snooped names
+	return append(snoopedNames, reverseNames...)
 }