Fix bug, add tests, and cli output

api/allocations.go

@@ -62,6 +62,7 @@ type Allocation struct {
 type AllocationMetric struct {
 	NodesEvaluated     int
 	NodesFiltered      int
+	NodesAvailable     map[string]int
 	ClassFiltered      map[string]int
 	ConstraintFiltered map[string]int
 	NodesExhausted     int

command/monitor.go

@@ -280,6 +280,14 @@ func dumpAllocStatus(ui cli.Ui, alloc *api.Allocation) {
 		ui.Output("  * No nodes were eligible for evaluation")
 	}
 
+	// Print a helpful message if the user has asked for a DC that has no
+	// available nodes.
+	for dc, available := range alloc.Metrics.NodesAvailable {
+		if available == 0 {
+			ui.Output(fmt.Sprintf("  * No nodes are available in datacenter %q", dc))
+		}
+	}
+
 	// Print filter info
 	for class, num := range alloc.Metrics.ClassFiltered {
 		ui.Output(fmt.Sprintf("  * Class %q filtered %d nodes", class, num))

scheduler/generic_sched.go

@@ -250,9 +250,6 @@ func (s *GenericScheduler) computePlacements(place []allocTuple) error {
 		return err
 	}
 
-	// Store the available nodes by datacenter
-	s.ctx.Metrics().NodesAvailable = byDC
-
 	// Update the set of placement ndoes
 	s.stack.SetNodes(nodes)
 
@@ -282,6 +279,9 @@ func (s *GenericScheduler) computePlacements(place []allocTuple) error {
 			Metrics:   s.ctx.Metrics(),
 		}
 
+		// Store the available nodes by datacenter
+		s.ctx.Metrics().NodesAvailable = byDC
+
 		// Set fields based on if we found an allocation option
 		if option != nil {
 			// Generate the service ids for the tasks which this allocation is going
@@ -303,5 +303,6 @@ func (s *GenericScheduler) computePlacements(place []allocTuple) error {
 			failedTG[missing.TaskGroup] = alloc
 		}
 	}
+
 	return nil
 }

scheduler/generic_sched_test.go

@@ -123,6 +123,11 @@ func TestServiceSched_JobRegister_AllocFail(t *testing.T) {
 		t.Fatalf("bad: %#v", out[0].Metrics)
 	}
 
+	// Check the available nodes
+	if count, ok := out[0].Metrics.NodesAvailable["dc1"]; !ok || count != 0 {
+		t.Fatalf("bad: %#v", out[0].Metrics)
+	}
+
 	h.AssertEvalStatus(t, structs.EvalStatusComplete)
 }
 

scheduler/system_sched.go

@@ -25,12 +25,13 @@ type SystemScheduler struct {
 	state   State
 	planner Planner
 
-	eval  *structs.Evaluation
-	job   *structs.Job
-	plan  *structs.Plan
-	ctx   *EvalContext
-	stack *SystemStack
-	nodes []*structs.Node
+	eval      *structs.Evaluation
+	job       *structs.Job
+	plan      *structs.Plan
+	ctx       *EvalContext
+	stack     *SystemStack
+	nodes     []*structs.Node
+	nodesByDC map[string]int
 
 	limitReached bool
 	nextEval     *structs.Evaluation
@@ -86,14 +87,10 @@ func (s *SystemScheduler) process() (bool, error) {
 
 	// Get the ready nodes in the required datacenters
 	if s.job != nil {
-		var byDC map[string]int
-		s.nodes, byDC, err = readyNodesInDCs(s.state, s.job.Datacenters)
+		s.nodes, s.nodesByDC, err = readyNodesInDCs(s.state, s.job.Datacenters)
 		if err != nil {
 			return false, fmt.Errorf("failed to get ready nodes: %v", err)
 		}
-
-		// Store the available nodes by datacenter
-		s.ctx.Metrics().NodesAvailable = byDC
 	}
 
 	// Create a plan
@@ -250,6 +247,9 @@ func (s *SystemScheduler) computePlacements(place []allocTuple) error {
 			Metrics:   s.ctx.Metrics(),
 		}
 
+		// Store the available nodes by datacenter
+		s.ctx.Metrics().NodesAvailable = s.nodesByDC
+
 		// Set fields based on if we found an allocation option
 		if option != nil {
 			// Generate the service ids for the tasks that this allocation is going

scheduler/system_sched_test.go

@@ -59,6 +59,11 @@ func TestSystemSched_JobRegister(t *testing.T) {
 		t.Fatalf("bad: %#v", out)
 	}
 
+	// Check the available nodes
+	if count, ok := out[0].Metrics.NodesAvailable["dc1"]; !ok || count != 10 {
+		t.Fatalf("bad: %#v", out[0].Metrics)
+	}
+
 	h.AssertEvalStatus(t, structs.EvalStatusComplete)
 }