perf: Cache list of nodes instead of retrieving the full list every time

go.mod

@@ -3,6 +3,7 @@ module github.com/TwiN/aws-eks-asg-rolling-update-handler
 go 1.16
 
 require (
+	github.com/TwiN/gocache/v2 v2.0.0
 	github.com/aws/aws-sdk-go v1.36.5
 	github.com/google/gofuzz v1.2.0 // indirect
 	github.com/googleapis/gnostic v0.5.3 // indirect

go.sum

@@ -57,6 +57,8 @@ github.com/PuerkitoBio/purell v1.1.1/go.mod h1:c11w/QuzBsJSee3cPx9rAFu61PvFxuPbt
 github.com/PuerkitoBio/urlesc v0.0.0-20160726150825-5bd2802263f2/go.mod h1:uGdkoq3SwY9Y+13GIhn11/XLaGBb4BfwItxLd5jeuXE=
 github.com/PuerkitoBio/urlesc v0.0.0-20170810143723-de5bf2ad4578 h1:d+Bc7a5rLufV/sSk/8dngufqelfh6jnri85riMAaF/M=
 github.com/PuerkitoBio/urlesc v0.0.0-20170810143723-de5bf2ad4578/go.mod h1:uGdkoq3SwY9Y+13GIhn11/XLaGBb4BfwItxLd5jeuXE=
+github.com/TwiN/gocache/v2 v2.0.0 h1:CPbDNKdSJpmBkh7aWcO7D3KK1yWaMlwX+3dsBPE8/so=
+github.com/TwiN/gocache/v2 v2.0.0/go.mod h1:j4MABVaia2Tp53ERWc/3l4YxkswtPjB2hQzmL/kD/VQ=
 github.com/alecthomas/template v0.0.0-20160405071501-a0175ee3bccc/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/template v0.0.0-20190718012654-fb15b899a751/go.mod h1:LOuyumcjzFXgccqObfd/Ljyb9UuFJ6TxHnclSeseNhc=
 github.com/alecthomas/units v0.0.0-20151022065526-2efee857e7cf/go.mod h1:ybxpYRFXyAe+OPACYpWeL0wqObRcbAqCMya13uyzqw0=

k8s/client.go

@@ -6,6 +6,7 @@ import (
 	"log"
 	"time"
 
+	"github.com/TwiN/gocache/v2"
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/autoscaling"
 	"k8s.io/api/core/v1"
@@ -18,6 +19,12 @@ const (
 	RollingUpdateStartedTimestampAnnotationKey    = "aws-eks-asg-rolling-update-handler/started-at"
 	RollingUpdateDrainedTimestampAnnotationKey    = "aws-eks-asg-rolling-update-handler/drained-at"
 	RollingUpdateTerminatedTimestampAnnotationKey = "aws-eks-asg-rolling-update-handler/terminated-at"
+
+	nodesCacheKey = "nodes"
+)
+
+var (
+	cache = gocache.NewCache().WithMaxSize(1000).WithEvictionPolicy(gocache.LeastRecentlyUsed)
 )
 
 type KubernetesClientApi interface {
@@ -42,10 +49,21 @@ func NewKubernetesClient(client *kubernetes.Clientset) *KubernetesClient {
 
 // GetNodes retrieves all nodes from the cluster
 func (k *KubernetesClient) GetNodes() ([]v1.Node, error) {
+	nodes, exists := cache.Get(nodesCacheKey)
+	if exists {
+		if v1Nodes, ok := nodes.([]v1.Node); ok {
+			// Return cached nodes
+			return v1Nodes, nil
+		} else {
+			log.Println("[k8s.GetNodes] Failed to cast cached nodes to []v1.Node; retrieving nodes from API instead")
+			cache.Delete(nodesCacheKey)
+		}
+	}
 	nodeList, err := k.client.CoreV1().Nodes().List(context.TODO(), metav1.ListOptions{})
 	if err != nil {
 		return nil, err
 	}
+	cache.SetWithTTL(nodesCacheKey, nodeList.Items, 10*time.Second)
 	return nodeList.Items, nil
 }