Ensure that the in-cluster is always scheduled on replica-0

api/autoscaler/common/load_index.go

@@ -43,6 +43,8 @@ func (s LoadIndexesDesc) Swap(i, j int) {
 	s[i], s[j] = s[j], s[i]
 }
 
+// Less returns true if the value of the LoadIndex at index i is greater than the value of the LoadIndex at index j.
+// Note that this is reversed because this is a descending sort implementation.
 func (s LoadIndexesDesc) Less(i, j int) bool {
 	return s[i].Value.AsApproximateFloat64() > s[j].Value.AsApproximateFloat64()
 }

partitioners/longestprocessingtime/longestprocessingtime.go

@@ -42,11 +42,10 @@ func (r *PartitionerImpl) Partition(ctx context.Context,
 		return replicas, nil
 	}
 
-	sort.Sort(common.LoadIndexesDesc(shards))
-	bucketSize := shards[0].Value.AsApproximateFloat64()
+	sortedShards, bucketSize := r.Sort(shards)
 
 	replicaCount := int32(0)
-	for _, shard := range shards {
+	for _, shard := range sortedShards {
 		// Find the replica with the least current load.
 		minLoad := float64(0)
 		selectedReplicaIndex := -1
@@ -89,3 +88,27 @@ func (r *PartitionerImpl) Partition(ctx context.Context,
 
 	return replicas, nil
 }
+
+func (r *PartitionerImpl) Sort(shards []common.LoadIndex) ([]common.LoadIndex, float64) {
+	if len(shards) == 0 {
+		return shards, 0
+	}
+
+	sortedShards := common.LoadIndexesDesc(shards)
+	sort.Sort(sortedShards)
+	biggestLoad := float64(sortedShards[0].Value.AsApproximateFloat64())
+
+	inClusterCondition := func(loadIndex common.LoadIndex) bool {
+		return loadIndex.Shard.Name == "in-cluster"
+	}
+	inClusterIndex := sort.Search(len(sortedShards), func(i int) bool {
+		return inClusterCondition(sortedShards[i])
+	})
+	if inClusterIndex < len(sortedShards) && inClusterCondition(sortedShards[inClusterIndex]) {
+		inClusterShard := sortedShards[inClusterIndex]
+		copy(sortedShards[inClusterIndex:], sortedShards[inClusterIndex+1:])
+		sortedShards = sortedShards[:len(sortedShards)-1]
+		return append(common.LoadIndexesDesc{inClusterShard}, sortedShards...), biggestLoad
+	}
+	return sortedShards, biggestLoad
+}

partitioners/longestprocessingtime/longestprocessingtime_test.go

@@ -0,0 +1,100 @@
+package longestprocessingtime
+
+import (
+	"context"
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	"github.com/plumber-cd/argocd-autoscaler/api/autoscaler/common"
+	"k8s.io/apimachinery/pkg/api/resource"
+)
+
+func TestControllers(t *testing.T) {
+	RegisterFailHandler(Fail)
+
+	RunSpecs(t, "LongestProcessingTimePartitioner Suite")
+}
+
+var _ = Describe("LongestProcessingTimePartitioner", func() {
+	Context("when unsorted list of shards", func() {
+		It("should sort", func() {
+			shards := []common.LoadIndex{
+				{Shard: common.Shard{Name: "shard1"}, Value: resource.MustParse("5")},
+				{Shard: common.Shard{Name: "shard2"}, Value: resource.MustParse("3")},
+				{Shard: common.Shard{Name: "shard3"}, Value: resource.MustParse("8")},
+				{Shard: common.Shard{Name: "shard4"}, Value: resource.MustParse("6")},
+				{Shard: common.Shard{Name: "shard5"}, Value: resource.MustParse("7")},
+			}
+			partitioner := PartitionerImpl{}
+			sortedShards, bucketSize := partitioner.Sort(shards)
+			Expect(bucketSize).To(Equal(float64(8)))
+			Expect(len(sortedShards)).To(Equal(len(shards)))
+			Expect(sortedShards[0].Shard.Name).To(Equal("shard3"))
+			Expect(sortedShards[1].Shard.Name).To(Equal("shard5"))
+			Expect(sortedShards[2].Shard.Name).To(Equal("shard4"))
+			Expect(sortedShards[3].Shard.Name).To(Equal("shard1"))
+			Expect(sortedShards[4].Shard.Name).To(Equal("shard2"))
+		})
+
+		It("should put in-cluster first", func() {
+			shards := []common.LoadIndex{
+				{Shard: common.Shard{Name: "shard1"}, Value: resource.MustParse("5")},
+				{Shard: common.Shard{Name: "shard2"}, Value: resource.MustParse("3")},
+				{Shard: common.Shard{Name: "shard3"}, Value: resource.MustParse("8")},
+				{Shard: common.Shard{Name: "in-cluster"}, Value: resource.MustParse("6")},
+				{Shard: common.Shard{Name: "shard5"}, Value: resource.MustParse("7")},
+			}
+			partitioner := PartitionerImpl{}
+			sortedShards, bucketSize := partitioner.Sort(shards)
+			Expect(bucketSize).To(Equal(float64(8)))
+			Expect(len(sortedShards)).To(Equal(len(shards)))
+			Expect(sortedShards[0].Shard.Name).To(Equal("in-cluster"))
+			Expect(sortedShards[1].Shard.Name).To(Equal("shard3"))
+			Expect(sortedShards[2].Shard.Name).To(Equal("shard5"))
+			Expect(sortedShards[3].Shard.Name).To(Equal("shard1"))
+			Expect(sortedShards[4].Shard.Name).To(Equal("shard2"))
+		})
+	})
+
+	Context("when partitioning", func() {
+		It("should partition", func() {
+			shards := []common.LoadIndex{
+				{Shard: common.Shard{Name: "shard1"}, Value: resource.MustParse("5")},
+				{Shard: common.Shard{Name: "shard2"}, Value: resource.MustParse("3")},
+				{Shard: common.Shard{Name: "shard3"}, Value: resource.MustParse("10")},
+				{Shard: common.Shard{Name: "in-cluster"}, Value: resource.MustParse("6")},
+				{Shard: common.Shard{Name: "shard5"}, Value: resource.MustParse("7")},
+			}
+			partitioner := PartitionerImpl{}
+			replicas, err := partitioner.Partition(context.TODO(), shards)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(replicas).To(HaveLen(4))
+
+			Expect(replicas[0].ID).To(Equal(int32(0)))
+			Expect(replicas[0].LoadIndexes).To(HaveLen(1))
+			Expect(replicas[0].LoadIndexes[0].Shard.Name).To(Equal("in-cluster"))
+			Expect(replicas[0].TotalLoad.AsApproximateFloat64()).To(Equal(float64(6)))
+			Expect(replicas[0].TotalLoadDisplayValue).To(Equal("6"))
+
+			Expect(replicas[1].ID).To(Equal(int32(1)))
+			Expect(replicas[1].LoadIndexes).To(HaveLen(1))
+			Expect(replicas[1].LoadIndexes[0].Shard.Name).To(Equal("shard3"))
+			Expect(replicas[1].TotalLoad.AsApproximateFloat64()).To(Equal(float64(10)))
+			Expect(replicas[1].TotalLoadDisplayValue).To(Equal("10"))
+
+			Expect(replicas[2].ID).To(Equal(int32(2)))
+			Expect(replicas[2].LoadIndexes).To(HaveLen(1))
+			Expect(replicas[2].LoadIndexes[0].Shard.Name).To(Equal("shard5"))
+			Expect(replicas[2].TotalLoad.AsApproximateFloat64()).To(Equal(float64(7)))
+			Expect(replicas[2].TotalLoadDisplayValue).To(Equal("7"))
+
+			Expect(replicas[3].ID).To(Equal(int32(3)))
+			Expect(replicas[3].LoadIndexes).To(HaveLen(2))
+			Expect(replicas[3].LoadIndexes[0].Shard.Name).To(Equal("shard1"))
+			Expect(replicas[3].LoadIndexes[1].Shard.Name).To(Equal("shard2"))
+			Expect(replicas[3].TotalLoad.AsApproximateFloat64()).To(Equal(float64(8)))
+			Expect(replicas[3].TotalLoadDisplayValue).To(Equal("8"))
+		})
+	})
+})