Merge pull request #64389 from yue9944882/top-nodes-print-missing-metrics

Automatic merge from submit-queue (batch tested with PRs 64882, 64692, 64389, 60626, 64840). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

print nodes for those metrics is somehow unreachable

**What this PR does / why we need it**:

When we use `kubectl top nodes`, some nodes will be ignored when their metrics cannot be fetched from metrics serve. It might be misleading for users.

This PR helps print the missing nodes like:

```
NAME                CPU(cores)   CPU%      MEMORY(bytes)   MEMORY%  
missing-nodes       -            -         -               -
```

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #63986

**Special notes for your reviewer**:

**Release note**:

```release-note
Fixes missing nodes lines when kubectl top nodes
```

pkg/kubectl/metricsutil/metrics_printer.go

@@ -76,6 +76,12 @@ func (printer *TopCmdPrinter) PrintNodeMetrics(metrics []metricsapi.NodeMetrics,
 			Metrics:   usage,
 			Available: availableResources[m.Name],
 		})
+		delete(availableResources, m.Name)
+	}
+
+	// print lines for nodes of which the metrics is unreachable.
+	for nodeName := range availableResources {
+		printMissingMetricsNodeLine(w, nodeName)
 	}
 	return nil
 }
@@ -171,6 +177,18 @@ func printMetricsLine(out io.Writer, metrics *ResourceMetricsInfo) {
 	fmt.Fprint(out, "\n")
 }
 
+func printMissingMetricsNodeLine(out io.Writer, nodeName string) {
+	printValue(out, nodeName)
+	unknownMetricsStatus := "<unknown>"
+	for i := 0; i < len(MeasuredResources); i++ {
+		printValue(out, unknownMetricsStatus)
+		printValue(out, "\t")
+		printValue(out, unknownMetricsStatus)
+		printValue(out, "\t")
+	}
+	fmt.Fprint(out, "\n")
+}
+
 func printValue(out io.Writer, value interface{}) {
 	fmt.Fprintf(out, "%v\t", value)
 }