Fix scoring logic for uneven spread to incorporate current alloc count

Also addressed other small code review comments

nomad/structs/structs.go

@@ -2191,7 +2191,7 @@ func (j *Job) Validate() error {
 
 	if j.Type == JobTypeSystem {
 		if j.Spreads != nil {
-			mErr.Errors = append(mErr.Errors, fmt.Errorf("System jobs may not have a s stanza"))
+			mErr.Errors = append(mErr.Errors, fmt.Errorf("System jobs may not have a spread stanza"))
 		}
 	} else {
 		for idx, spread := range j.Spreads {
@@ -5479,7 +5479,7 @@ func (s *Spread) Validate() error {
 		sumPercent += target.Percent
 	}
 	if sumPercent > 100 {
-		mErr.Errors = append(mErr.Errors, errors.New("Sum of spread target percentages must not be greater than 100"))
+		mErr.Errors = append(mErr.Errors, errors.New(fmt.Sprintf("Sum of spread target percentages must not be greater than 100%%; got %d%%", sumPercent)))
 	}
 	return mErr.ErrorOrNil()
 }

nomad/structs/structs_test.go

@@ -4004,7 +4004,7 @@ func TestSpread_Validate(t *testing.T) {
 					},
 				},
 			},
-			err:  fmt.Errorf("Sum of spread target percentages must not be greater than 100"),
+			err:  fmt.Errorf("Sum of spread target percentages must not be greater than 100%%; got %d%%", 150),
 			name: "Invalid percentages",
 		},
 		{

scheduler/generic_sched_test.go

@@ -604,10 +604,104 @@ func TestServiceSched_JobRegister_DistinctProperty_TaskGroup_Incr(t *testing.T)
 
 // Test job registration with spread configured
 func TestServiceSched_Spread(t *testing.T) {
-	h := NewHarness(t)
 	assert := assert.New(t)
 
-	// Create a job that uses spread over data center
+	start := uint32(100)
+	step := uint32(10)
+
+	for i := 0; i < 10; i++ {
+		name := fmt.Sprintf("%d%% in dc1", start)
+		t.Run(name, func(t *testing.T) {
+			h := NewHarness(t)
+			remaining := uint32(100 - start)
+			// Create a job that uses spread over data center
+			job := mock.Job()
+			job.Datacenters = []string{"dc1", "dc2"}
+			job.TaskGroups[0].Count = 10
+			job.TaskGroups[0].Spreads = append(job.TaskGroups[0].Spreads,
+				&structs.Spread{
+					Attribute: "${node.datacenter}",
+					Weight:    100,
+					SpreadTarget: []*structs.SpreadTarget{
+						{
+							Value:   "dc1",
+							Percent: start,
+						},
+						{
+							Value:   "dc2",
+							Percent: remaining,
+						},
+					},
+				})
+			assert.Nil(h.State.UpsertJob(h.NextIndex(), job), "UpsertJob")
+			// Create some nodes, half in dc2
+			var nodes []*structs.Node
+			nodeMap := make(map[string]*structs.Node)
+			for i := 0; i < 10; i++ {
+				node := mock.Node()
+				if i%2 == 0 {
+					node.Datacenter = "dc2"
+				}
+				nodes = append(nodes, node)
+				assert.Nil(h.State.UpsertNode(h.NextIndex(), node), "UpsertNode")
+				nodeMap[node.ID] = node
+			}
+
+			// Create a mock evaluation to register the job
+			eval := &structs.Evaluation{
+				Namespace:   structs.DefaultNamespace,
+				ID:          uuid.Generate(),
+				Priority:    job.Priority,
+				TriggeredBy: structs.EvalTriggerJobRegister,
+				JobID:       job.ID,
+				Status:      structs.EvalStatusPending,
+			}
+			noErr(t, h.State.UpsertEvals(h.NextIndex(), []*structs.Evaluation{eval}))
+
+			// Process the evaluation
+			assert.Nil(h.Process(NewServiceScheduler, eval), "Process")
+
+			// Ensure a single plan
+			assert.Len(h.Plans, 1, "Number of plans")
+			plan := h.Plans[0]
+
+			// Ensure the plan doesn't have annotations.
+			assert.Nil(plan.Annotations, "Plan.Annotations")
+
+			// Ensure the eval hasn't spawned blocked eval
+			assert.Len(h.CreateEvals, 0, "Created Evals")
+
+			// Ensure the plan allocated
+			var planned []*structs.Allocation
+			dcAllocsMap := make(map[string]int)
+			for nodeId, allocList := range plan.NodeAllocation {
+				planned = append(planned, allocList...)
+				dc := nodeMap[nodeId].Datacenter
+				c := dcAllocsMap[dc]
+				c += len(allocList)
+				dcAllocsMap[dc] = c
+			}
+			assert.Len(planned, 10, "Planned Allocations")
+
+			expectedCounts := make(map[string]int)
+			expectedCounts["dc1"] = 10 - i
+			if i > 0 {
+				expectedCounts["dc2"] = i
+			}
+			require.Equal(t, expectedCounts, dcAllocsMap)
+
+			h.AssertEvalStatus(t, structs.EvalStatusComplete)
+		})
+		start = start - step
+	}
+}
+
+// Test job registration with even spread across dc
+func TestServiceSched_EvenSpread(t *testing.T) {
+	assert := assert.New(t)
+
+	h := NewHarness(t)
+	// Create a job that uses even spread over data center
 	job := mock.Job()
 	job.Datacenters = []string{"dc1", "dc2"}
 	job.TaskGroups[0].Count = 10
@@ -615,23 +709,12 @@ func TestServiceSched_Spread(t *testing.T) {
 		&structs.Spread{
 			Attribute: "${node.datacenter}",
 			Weight:    100,
-			SpreadTarget: []*structs.SpreadTarget{
-				{
-					Value:   "dc1",
-					Percent: 70,
-				},
-				{
-					Value:   "dc2",
-					Percent: 30,
-				},
-			},
 		})
 	assert.Nil(h.State.UpsertJob(h.NextIndex(), job), "UpsertJob")
-
 	// Create some nodes, half in dc2
 	var nodes []*structs.Node
 	nodeMap := make(map[string]*structs.Node)
-	for i := 0; i < 6; i++ {
+	for i := 0; i < 10; i++ {
 		node := mock.Node()
 		if i%2 == 0 {
 			node.Datacenter = "dc2"
@@ -677,9 +760,11 @@ func TestServiceSched_Spread(t *testing.T) {
 	}
 	assert.Len(planned, 10, "Planned Allocations")
 
+	// Expect even split allocs across datacenter
 	expectedCounts := make(map[string]int)
-	expectedCounts["dc1"] = 7
+	expectedCounts["dc1"] = 5
-	expectedCounts["dc2"] = 3
+	expectedCounts["dc2"] = 5
+
 	require.Equal(t, expectedCounts, dcAllocsMap)
 
 	h.AssertEvalStatus(t, structs.EvalStatusComplete)

scheduler/spread.go

@@ -123,6 +123,8 @@ func (iter *SpreadIterator) Next() *RankedNode {
 		for _, pset := range propertySets {
 			nValue, errorMsg, usedCount := pset.UsedCount(option.Node, tgName)
 
+			// Add one to include placement on this node in the scoring calculation
+			usedCount += 1
 			// Set score to -1 if there were errors in building this attribute
 			if errorMsg != "" {
 				iter.ctx.Logger().Printf("[WARN] sched: error building spread attributes for task group %v:%v", tgName, errorMsg)
@@ -182,13 +184,12 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 	}
 	// Get the nodes property value
 	nValue, ok := getProperty(option, pset.targetAttribute)
-	currentAttributeCount := uint64(0)
+
-	if ok {
+	// Maximum possible penalty when the attribute isn't set on the node
-		currentAttributeCount = combinedUseMap[nValue]
+	if !ok {
-	} else {
-		// If the attribute isn't set on the node, it should get the maximum possible penalty
 		return -1.0
 	}
+	currentAttributeCount := combinedUseMap[nValue]
 	minCount := uint64(0)
 	maxCount := uint64(0)
 	for _, value := range combinedUseMap {
@@ -211,17 +212,15 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 	if currentAttributeCount != minCount {
 		// Boost based on delta between current and min
 		return deltaBoost
-	} else {
+	} else if minCount == maxCount {
-		if minCount == maxCount {
+		// Maximum possible penalty when the distribution is even
-			// Maximum possible penalty when the distribution is even
+		return -1.0
-			return -1.0
-		} else {
-			// Penalty based on delta from max value
-			delta := int(maxCount - minCount)
-			deltaBoost = float64(delta) / float64(minCount)
-			return deltaBoost
-		}
 	}
+	// Penalty based on delta from max value
+	delta := int(maxCount - minCount)
+	deltaBoost = float64(delta) / float64(minCount)
+	return deltaBoost
+
 }
 
 // computeSpreadInfo computes and stores percentages and total values

scheduler/spread_test.go

@@ -30,7 +30,7 @@ func TestSpreadIterator_SingleAttribute(t *testing.T) {
 
 	job := mock.Job()
 	tg := job.TaskGroups[0]
-	job.TaskGroups[0].Count = 5
+	job.TaskGroups[0].Count = 10
 	// add allocs to nodes in dc1
 	upserting := []*structs.Allocation{
 		{
@@ -79,11 +79,11 @@ func TestSpreadIterator_SingleAttribute(t *testing.T) {
 	out := collectRanked(scoreNorm)
 
 	// Expect nodes in dc1 with existing allocs to get a boost
-	// Boost should be ((desiredCount-actual)/expected)*spreadWeight
+	// Boost should be ((desiredCount-actual)/desired)*spreadWeight
-	// For this test, that becomes dc1 = ((4-2)/4 ) = 0.5, and dc2=(1-0)/1
+	// For this test, that becomes dc1 = ((8-3)/8 ) = 0.5, and dc2=(2-1)/2
 	expectedScores := map[string]float64{
-		"dc1": 0.5,
+		"dc1": 0.625,
-		"dc2": 1.0,
+		"dc2": 0.5,
 	}
 	for _, rn := range out {
 		require.Equal(t, expectedScores[rn.Node.Datacenter], rn.FinalScore)
@@ -92,6 +92,14 @@ func TestSpreadIterator_SingleAttribute(t *testing.T) {
 	// Update the plan to add more allocs to nodes in dc1
 	// After this step there are enough allocs to meet the desired count in dc1
 	ctx.plan.NodeAllocation[nodes[0].Node.ID] = []*structs.Allocation{
+		{
+			Namespace: structs.DefaultNamespace,
+			TaskGroup: tg.Name,
+			JobID:     job.ID,
+			Job:       job,
+			ID:        uuid.Generate(),
+			NodeID:    nodes[0].Node.ID,
+		},
 		{
 			Namespace: structs.DefaultNamespace,
 			TaskGroup: tg.Name,
@@ -119,6 +127,22 @@ func TestSpreadIterator_SingleAttribute(t *testing.T) {
 			ID:        uuid.Generate(),
 			NodeID:    nodes[3].Node.ID,
 		},
+		{
+			Namespace: structs.DefaultNamespace,
+			TaskGroup: tg.Name,
+			JobID:     job.ID,
+			Job:       job,
+			ID:        uuid.Generate(),
+			NodeID:    nodes[3].Node.ID,
+		},
+		{
+			Namespace: structs.DefaultNamespace,
+			TaskGroup: tg.Name,
+			JobID:     job.ID,
+			Job:       job,
+			ID:        uuid.Generate(),
+			NodeID:    nodes[3].Node.ID,
+		},
 	}
 
 	// Reset the scores
@@ -138,7 +162,7 @@ func TestSpreadIterator_SingleAttribute(t *testing.T) {
 	// the desired count
 	expectedScores = map[string]float64{
 		"dc1": 0,
-		"dc2": 1.0,
+		"dc2": 0.5,
 	}
 	for _, rn := range out {
 		require.Equal(t, expectedScores[rn.Node.Datacenter], rn.FinalScore)
@@ -166,7 +190,7 @@ func TestSpreadIterator_MultipleAttributes(t *testing.T) {
 
 	job := mock.Job()
 	tg := job.TaskGroups[0]
-	job.TaskGroups[0].Count = 5
+	job.TaskGroups[0].Count = 10
 	// add allocs to nodes in dc1
 	upserting := []*structs.Allocation{
 		{
@@ -232,13 +256,13 @@ func TestSpreadIterator_MultipleAttributes(t *testing.T) {
 
 	out := collectRanked(scoreNorm)
 
-	// Score come from combining two different spread factors
+	// Score comes from combining two different spread factors
 	// Second node should have the highest score because it has no allocs and its in dc2/r1
 	expectedScores := map[string]float64{
-		nodes[0].Node.ID: 0.389,
+		nodes[0].Node.ID: 0.500,
-		nodes[1].Node.ID: 0.833,
+		nodes[1].Node.ID: 0.667,
-		nodes[2].Node.ID: 0.444,
+		nodes[2].Node.ID: 0.556,
-		nodes[3].Node.ID: 0.444,
+		nodes[3].Node.ID: 0.556,
 	}
 	for _, rn := range out {
 		require.Equal(t, fmt.Sprintf("%.3f", expectedScores[rn.Node.ID]), fmt.Sprintf("%.3f", rn.FinalScore))