Issue #2258 Reafctor ready pod conroller to use lister and cache sync checks (#2259)

Reactored ready pod controller code to user lister and cache sync checks,
so that we avoid querying lister if cache is not synced in choodPod function.
Also, as noticied in #2258 we were initializing workqueue in goroutine
which was causing nil pointer reference. We have moved it out of goroutine
and kept specific parts in goroutine.

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

pkg/utils/informer.go

@@ -13,6 +13,16 @@ import (
 	v1 "github.com/fission/fission/pkg/apis/core/v1"
 )
 
+func GetInformerFactoryByReadyPod(client *kubernetes.Clientset, namespace string, labelSelector *metav1.LabelSelector) (k8sInformers.SharedInformerFactory, error) {
+	informerFactory := k8sInformers.NewSharedInformerFactoryWithOptions(client, 0,
+		k8sInformers.WithNamespace(namespace),
+		k8sInformers.WithTweakListOptions(func(options *metav1.ListOptions) {
+			options.LabelSelector = labels.Set(labelSelector.MatchLabels).AsSelector().String()
+			options.FieldSelector = "status.phase=Running"
+		}))
+	return informerFactory, nil
+}
+
 func GetInformerFactoryByExecutor(client *kubernetes.Clientset, executorType v1.ExecutorType, defaultResync time.Duration) (k8sInformers.SharedInformerFactory, error) {
 	executorLabel, err := labels.NewRequirement(v1.EXECUTOR_TYPE, selection.DoubleEquals, []string{string(executorType)})
 	if err != nil {