Add a SharedIndexInformer for services and deployments to NewDeploy executor (#2061)

* Add a SharedIndexInformer for services and deployments to NewDeploy executor.

This brings the NewDeploy executor behaviour into sync with GenericPoolManager behaviour
by caching Kubernetes services and deployments used in per-request function validation.

* Create informers in executer by executor label

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>

Co-authored-by: James Sinclair <irgeek@btc.com.au>

pkg/utils/informer.go

@@ -0,0 +1,24 @@
+package utils
+
+import (
+	v1 "github.com/fission/fission/pkg/apis/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/labels"
+	"k8s.io/apimachinery/pkg/selection"
+	k8sInformers "k8s.io/client-go/informers"
+	"k8s.io/client-go/kubernetes"
+)
+
+func GetInformerFacoryByExecutor(client *kubernetes.Clientset, executorType v1.ExecutorType) (k8sInformers.SharedInformerFactory, error) {
+	executorLabel, err := labels.NewRequirement(v1.EXECUTOR_TYPE, selection.DoubleEquals, []string{string(executorType)})
+	if err != nil {
+		return nil, err
+	}
+	labelSelector := labels.NewSelector()
+	labelSelector.Add(*executorLabel)
+	informerFactory := k8sInformers.NewSharedInformerFactoryWithOptions(client, 0,
+		k8sInformers.WithTweakListOptions(func(options *metav1.ListOptions) {
+			options.LabelSelector = labelSelector.String()
+		}))
+	return informerFactory, nil
+}