command: print a warning if we get 0 evaluated nodes

command/monitor.go

@@ -272,6 +272,11 @@ func dumpAllocStatus(ui cli.Ui, alloc *api.Allocation) {
 		alloc.ID, alloc.ClientStatus,
 		alloc.Metrics.NodesFiltered, alloc.Metrics.NodesEvaluated))
 
+	// Print a helpful message if we have an eligibility problem
+	if alloc.Metrics.NodesEvaluated == 0 {
+		ui.Output("  * No nodes were eligible for evaluation")
+	}
+
 	// Print filter info
 	for class, num := range alloc.Metrics.ClassFiltered {
 		ui.Output(fmt.Sprintf("  * Class %q filtered %d nodes", class, num))

command/monitor_test.go

@@ -326,4 +326,15 @@ func TestMonitor_DumpAllocStatus(t *testing.T) {
 	if !strings.Contains(out, `Dimension "cpu" exhausted on 1 nodes`) {
 		t.Fatalf("missing dimension exhaustion\n\n%s", out)
 	}
+	ui.OutputWriter.Reset()
+
+	// Dumping alloc status with no eligible nodes adds a warning
+	alloc.Metrics.NodesEvaluated = 0
+	dumpAllocStatus(ui, alloc)
+
+	// Check the output
+	out = ui.OutputWriter.String()
+	if !strings.Contains(out, "No nodes were eligible") {
+		t.Fatalf("missing eligibility warning\n\n%s", out)
+	}
 }