Figure out whether to show host tags in details pane from context

app/api_topology.go

@@ -68,7 +68,7 @@ func handleNode(rep xfer.Reporter, t topologyView, w http.ResponseWriter, r *htt
 		http.NotFound(w, r)
 		return
 	}
-	respondWith(w, http.StatusOK, APINode{Node: render.MakeDetailedNode(rpt, node, t.isMultiHost)})
+	respondWith(w, http.StatusOK, APINode{Node: render.MakeDetailedNode(rpt, node)})
 }
 
 // Individual edges.

app/router.go

@@ -107,10 +107,9 @@ var topologyRegistry = map[string]topologyView{
 		renderer: render.FilterUnconnected{Renderer: render.ProcessWithContainerNameRenderer{}},
 	},
 	"applications-by-name": {
-		human:       "by name",
-		parent:      "applications",
-		renderer:    render.FilterUnconnected{Renderer: render.ProcessNameRenderer},
-		isMultiHost: true,
+		human:    "by name",
+		parent:   "applications",
+		renderer: render.FilterUnconnected{Renderer: render.ProcessNameRenderer},
 	},
 	"containers": {
 		human:    "Containers",
@@ -118,10 +117,9 @@ var topologyRegistry = map[string]topologyView{
 		renderer: render.ContainerRenderer,
 	},
 	"containers-by-image": {
-		human:       "by image",
-		parent:      "containers",
-		renderer:    render.ContainerImageRenderer,
-		isMultiHost: true,
+		human:    "by image",
+		parent:   "containers",
+		renderer: render.ContainerImageRenderer,
 	},
 	"hosts": {
 		human:    "Hosts",
@@ -131,8 +129,7 @@ var topologyRegistry = map[string]topologyView{
 }
 
 type topologyView struct {
-	human       string
-	parent      string
-	renderer    render.Renderer
-	isMultiHost bool // does the view involve information from multiple hosts?
+	human    string
+	parent   string
+	renderer render.Renderer
 }

render/detailed_node.go

@@ -72,15 +72,28 @@ func (t sortableTables) Less(i, j int) bool { return t[i].Rank > t[j].Rank }
 
 // MakeDetailedNode transforms a renderable node to a detailed node. It uses
 // aggregate metadata, plus the set of origin node IDs, to produce tables.
-func MakeDetailedNode(r report.Report, n RenderableNode, addHostTags bool) DetailedNode {
+func MakeDetailedNode(r report.Report, n RenderableNode) DetailedNode {
 	tables := sortableTables{}
+
+	// Figure out if multiple hosts are referenced by the renderableNode
+	originHosts := make(map[string]struct{})
+	for _, id := range n.Origins {
+		for _, topology := range r.Topologies() {
+			if nmd, ok := topology.NodeMetadatas[id]; ok {
+				originHosts[report.ExtractHostID(nmd)] = struct{}{}
+				break
+			}
+		}
+	}
+	multiHost := len(originHosts) > 1
+
 	// RenderableNode may be the result of merge operation(s), and so may have
 	// multiple origins. The ultimate goal here is to generate tables to view
 	// in the UI, so we skip the intermediate representations, but we could
 	// add them later.
 	connections := []Row{}
 	for _, id := range n.Origins {
-		if table, ok := OriginTable(r, id, addHostTags); ok {
+		if table, ok := OriginTable(r, id, multiHost); ok {
 			tables = append(tables, table)
 		} else if _, ok := r.Endpoint.NodeMetadatas[id]; ok {
 			connections = append(connections, connectionDetailsRows(r.Endpoint, id)...)

render/detailed_node_test.go

@@ -74,7 +74,7 @@ func TestOriginTable(t *testing.T) {
 
 func TestMakeDetailedHostNode(t *testing.T) {
 	renderableNode := render.HostRenderer.Render(test.Report)[render.MakeHostID(test.ClientHostID)]
-	have := render.MakeDetailedNode(test.Report, renderableNode, false)
+	have := render.MakeDetailedNode(test.Report, renderableNode)
 	want := render.DetailedNode{
 		ID:         render.MakeHostID(test.ClientHostID),
 		LabelMajor: "client",
@@ -131,7 +131,7 @@ func TestMakeDetailedHostNode(t *testing.T) {
 
 func TestMakeDetailedContainerNode(t *testing.T) {
 	renderableNode := render.ContainerRenderer.Render(test.Report)[test.ServerContainerID]
-	have := render.MakeDetailedNode(test.Report, renderableNode, false)
+	have := render.MakeDetailedNode(test.Report, renderableNode)
 	want := render.DetailedNode{
 		ID:         test.ServerContainerID,
 		LabelMajor: "server",