From ea843a507a54b7eb3d8de8babf0f950e90624a40 Mon Sep 17 00:00:00 2001
From: Nick Ethier <nethier@hashicorp.com>
Date: Wed, 15 May 2019 13:00:24 -0400
Subject: [PATCH 1/3] scheduler: add check to prohibit returning inf during
 spread boost calculation

---
 scheduler/spread.go      |  6 +++++-
 scheduler/spread_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/scheduler/spread.go b/scheduler/spread.go
index 669a7507904..36bdcc16bb5 100644
--- a/scheduler/spread.go
+++ b/scheduler/spread.go
@@ -194,7 +194,7 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 	for _, value := range combinedUseMap {
 		if minCount == 0 || value < minCount {
 			minCount = value
-		}
+
 		if maxCount == 0 || value > maxCount {
 			maxCount = value
 		}
@@ -214,7 +214,11 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 	} else if minCount == maxCount {
 		// Maximum possible penalty when the distribution is even
 		return -1.0
+	} else if minCount == 0 {
+		// Maximum possible boost
+		return 1.0
 	}
+
 	// Penalty based on delta from max value
 	delta := int(maxCount - minCount)
 	deltaBoost = float64(delta) / float64(minCount)
diff --git a/scheduler/spread_test.go b/scheduler/spread_test.go
index 83fb2749f94..bc7532314f0 100644
--- a/scheduler/spread_test.go
+++ b/scheduler/spread_test.go
@@ -1,6 +1,7 @@
 package scheduler
 
 import (
+	"math"
 	"testing"
 
 	"fmt"
@@ -311,6 +312,7 @@ func TestSpreadIterator_EvenSpread(t *testing.T) {
 	}
 	for _, rn := range out {
 		require.Equal(t, fmt.Sprintf("%.3f", expectedScores[rn.Node.Datacenter]), fmt.Sprintf("%.3f", rn.FinalScore))
+
 	}
 
 	// Update the plan to add allocs to nodes in dc1
@@ -543,3 +545,25 @@ func TestSpreadIterator_MaxPenalty(t *testing.T) {
 	}
 
 }
+
+func Test_evenSpreadScoreBoost(t *testing.T) {
+	pset := &propertySet{
+		existingValues: map[string]uint64{},
+		proposedValues: map[string]uint64{
+			"dc2": 1,
+			"dc1": 1,
+			"dc3": 1,
+		},
+		clearedValues: map[string]uint64{
+			"dc2": 1,
+			"dc3": 1,
+		},
+		targetAttribute: "${node.datacenter}",
+	}
+
+	opt := &structs.Node{
+		Datacenter: "dc2",
+	}
+	boost := evenSpreadScoreBoost(pset, opt)
+	require.False(t, math.IsInf(boost, 1))
+}

From 5709bf7b546b8f13ea552ccda30eb073e0306e7a Mon Sep 17 00:00:00 2001
From: Nick Ethier <nethier@hashicorp.com>
Date: Wed, 15 May 2019 13:02:04 -0400
Subject: [PATCH 2/3] fix missing brace

---
 scheduler/spread.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scheduler/spread.go b/scheduler/spread.go
index 36bdcc16bb5..1e4961308e9 100644
--- a/scheduler/spread.go
+++ b/scheduler/spread.go
@@ -194,7 +194,7 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 	for _, value := range combinedUseMap {
 		if minCount == 0 || value < minCount {
 			minCount = value
-
+		}
 		if maxCount == 0 || value > maxCount {
 			maxCount = value
 		}

From 566dd71486107caf3efb516664b28ecd6386d176 Mon Sep 17 00:00:00 2001
From: Preetha Appan <preetha@hashicorp.com>
Date: Wed, 15 May 2019 12:35:57 -0500
Subject: [PATCH 3/3] Fix comment and assert score in test case

---
 scheduler/spread.go      | 3 ++-
 scheduler/spread_test.go | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/scheduler/spread.go b/scheduler/spread.go
index 1e4961308e9..41846382dfa 100644
--- a/scheduler/spread.go
+++ b/scheduler/spread.go
@@ -215,7 +215,8 @@ func evenSpreadScoreBoost(pset *propertySet, option *structs.Node) float64 {
 		// Maximum possible penalty when the distribution is even
 		return -1.0
 	} else if minCount == 0 {
-		// Maximum possible boost
+		// Current attribute count is equal to min and both are zero. This means no allocations
+		// were placed for this attribute value yet. Should get the maximum possible boost.
 		return 1.0
 	}
 
diff --git a/scheduler/spread_test.go b/scheduler/spread_test.go
index bc7532314f0..9b6d6309dc6 100644
--- a/scheduler/spread_test.go
+++ b/scheduler/spread_test.go
@@ -566,4 +566,5 @@ func Test_evenSpreadScoreBoost(t *testing.T) {
 	}
 	boost := evenSpreadScoreBoost(pset, opt)
 	require.False(t, math.IsInf(boost, 1))
+	require.Equal(t, 1.0, boost)
 }