show nice column labels when no children have metrics

client/app/scripts/components/node-details/node-details-table.js

@@ -70,18 +70,7 @@ export default class NodeDetailsTable extends React.Component {
 
   renderHeaders() {
     if (this.props.nodes && this.props.nodes.length > 0) {
-      let headers = [{id: 'label', label: this.props.label}];
-      // gather header labels from metrics and metadata
-      const nodeValues = this.props.nodes.map(this.getValuesForNode);
-      headers = headers.concat(this.props.columns.map(column => {
-        // look for a node that has the column label
-        const valuesWithField = nodeValues.find(values => values[column] !== undefined);
-        if (valuesWithField) {
-          return {id: column, label: valuesWithField[column].label};
-        }
-        // fall back on column id as label
-        return {id: column, label: column};
-      }));
+      const headers = [{id: 'label', label: this.props.label}].concat(this.props.columns);
       const defaultSortBy = this.getDefaultSortBy();
 
       return (
@@ -114,8 +103,8 @@ export default class NodeDetailsTable extends React.Component {
 
   renderValues(node) {
     const fields = this.getValuesForNode(node);
-    return this.props.columns.map(col => {
-      const field = fields[col];
+    return this.props.columns.map(({id}) => {
+      const field = fields[id];
       if (field) {
         if (field.valueType === 'metadata') {
           return (

render/detailed/node.go

@@ -83,11 +83,11 @@ var (
 		topologyID string
 		NodeSummaryGroup
 	}{
-		{report.Host, NodeSummaryGroup{TopologyID: "hosts", Label: "Hosts", Columns: []string{host.CPUUsage, host.MemoryUsage}}},
-		{report.Pod, NodeSummaryGroup{TopologyID: "pods", Label: "Pods", Columns: []string{}}},
-		{report.Container, NodeSummaryGroup{TopologyID: "containers", Label: "Containers", Columns: []string{docker.CPUTotalUsage, docker.MemoryUsage}}},
-		{report.Process, NodeSummaryGroup{TopologyID: "processes", Label: "Processes", Columns: []string{process.PID, process.CPUUsage, process.MemoryUsage}}},
-		{report.ContainerImage, NodeSummaryGroup{TopologyID: "containers-by-image", Label: "Container Images", Columns: []string{render.ContainersKey}}},
+		{report.Host, NodeSummaryGroup{TopologyID: "hosts", Label: "Hosts", Columns: []Column{host.CPUUsage, host.MemoryUsage}}},
+		{report.Pod, NodeSummaryGroup{TopologyID: "pods", Label: "Pods"}},
+		{report.Container, NodeSummaryGroup{TopologyID: "containers", Label: "Containers", Columns: []Column{docker.CPUTotalUsage, docker.MemoryUsage}}},
+		{report.Process, NodeSummaryGroup{TopologyID: "processes", Label: "Processes", Columns: []Column{process.PID, process.CPUUsage, process.MemoryUsage}}},
+		{report.ContainerImage, NodeSummaryGroup{TopologyID: "containers-by-image", Label: "Container Images", Columns: []Column{render.ContainersKey}}},
 	}
 )
 

render/detailed/node_test.go

@@ -85,19 +85,19 @@ func TestMakeDetailedHostNode(t *testing.T) {
 			{
 				Label:      "Containers",
 				TopologyID: "containers",
-				Columns:    []string{docker.CPUTotalUsage, docker.MemoryUsage},
+				Columns:    []detailed.Column{docker.CPUTotalUsage, docker.MemoryUsage},
 				Nodes:      []detailed.NodeSummary{containerNodeSummary},
 			},
 			{
 				Label:      "Processes",
 				TopologyID: "processes",
-				Columns:    []string{process.PID, process.CPUUsage, process.MemoryUsage},
+				Columns:    []detailed.Column{process.PID, process.CPUUsage, process.MemoryUsage},
 				Nodes:      []detailed.NodeSummary{process1NodeSummary, process2NodeSummary},
 			},
 			{
 				Label:      "Container Images",
 				TopologyID: "containers-by-image",
-				Columns:    []string{render.ContainersKey},
+				Columns:    []detailed.Column{render.ContainersKey},
 				Nodes:      []detailed.NodeSummary{containerImageNodeSummary},
 			},
 		},
@@ -152,7 +152,7 @@ func TestMakeDetailedContainerNode(t *testing.T) {
 			{
 				Label:      "Processes",
 				TopologyID: "processes",
-				Columns:    []string{process.PID, process.CPUUsage, process.MemoryUsage},
+				Columns:    []detailed.Column{process.PID, process.CPUUsage, process.MemoryUsage},
 				Nodes: []detailed.NodeSummary{
 					{
 						ID:       fmt.Sprintf("process:%s:%s", "server.hostname.com", fixture.ServerPID),

render/detailed/summary.go

@@ -1,6 +1,7 @@
 package detailed
 
 import (
+	"encoding/json"
 	"fmt"
 
 	"github.com/weaveworks/scope/probe/docker"
@@ -16,7 +17,7 @@ type NodeSummaryGroup struct {
 	Label      string        `json:"label"`
 	Nodes      []NodeSummary `json:"nodes"`
 	TopologyID string        `json:"topologyId"`
-	Columns    []string      `json:"columns"`
+	Columns    []Column      `json:"columns"`
 }
 
 // Copy returns a value copy of the NodeSummaryGroup
@@ -32,6 +33,25 @@ func (g NodeSummaryGroup) Copy() NodeSummaryGroup {
 	return result
 }
 
+// Column provides special json serialization for column ids, so they include
+// their label for the frontend.
+type Column string
+
+// MarshalJSON serializes a column to json
+func (c Column) MarshalJSON() ([]byte, error) {
+	return json.Marshal(map[string]string{"id": string(c), "label": Label(string(c))})
+}
+
+// UnmarshalJSON deserializes a column from json
+func (c *Column) UnmarshalJSON(b []byte) error {
+	m := map[string]string{}
+	if err := json.Unmarshal(b, &m); err != nil {
+		return err
+	}
+	*c = Column(m["id"])
+	return nil
+}
+
 // NodeSummary is summary information about a child for a Node.
 type NodeSummary struct {
 	ID           string        `json:"id"`