Allow namespace configuration for different CRD resources in Fission (#2539)

* Allow multiple namespaces for builder manager
* Enable multiple namespaces for executor informers
* Added missing context
* helm chart support for multiple namespaces
* Directly consume map type from GetInformerForNamespaces fn
* Optimize function resolver by choosing namespace-specific informer
* helm chart support for multiple namespaces
* consider default namespace and move duplicate code to helm template
* Improve documentation for fission namespace values

Signed-off-by: Sanket Sudake <sanketsudake@gmail.com>
Co-authored-by: shubham bansal <shubhambansaliimtgn@gmail.com>

pkg/utils/informer.go

@@ -1,6 +1,8 @@
 package utils
 
 import (
+	"os"
+	"strings"
 	"time"
 
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -8,11 +10,65 @@ import (
 	"k8s.io/apimachinery/pkg/selection"
 	k8sInformers "k8s.io/client-go/informers"
 	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/tools/cache"
 	metricsapi "k8s.io/metrics/pkg/apis/metrics"
 
 	v1 "github.com/fission/fission/pkg/apis/core/v1"
+
+	fv1 "github.com/fission/fission/pkg/apis/core/v1"
+	"github.com/fission/fission/pkg/generated/clientset/versioned"
+	genInformer "github.com/fission/fission/pkg/generated/informers/externalversions"
 )
 
+const additionalNamespaces string = "FISSION_RESOURCE_NAMESPACES"
+
+func GetNamespaces() []string {
+	envValue := os.Getenv(additionalNamespaces)
+	if len(envValue) == 0 {
+		return []string{
+			metav1.NamespaceAll,
+		}
+	}
+
+	informerNS := make([]string, 0)
+	lstNamespaces := strings.Split(envValue, ",")
+	for _, namespace := range lstNamespaces {
+		//check to handle string with additional comma at the end of string. eg- ns1,ns2,
+		if namespace != "" {
+			informerNS = append(informerNS, namespace)
+		}
+	}
+	return informerNS
+}
+
+func GetInformersForNamespaces(client versioned.Interface, defaultSync time.Duration, kind string) map[string]cache.SharedIndexInformer {
+	informers := make(map[string]cache.SharedIndexInformer)
+	for _, ns := range GetNamespaces() {
+		factory := genInformer.NewFilteredSharedInformerFactory(client, defaultSync, ns, nil).Core().V1()
+		switch kind {
+		case fv1.CanaryConfigResource:
+			informers[ns] = factory.CanaryConfigs().Informer()
+		case fv1.EnvironmentResource:
+			informers[ns] = factory.Environments().Informer()
+		case fv1.FunctionResource:
+			informers[ns] = factory.Functions().Informer()
+		case fv1.HttpTriggerResource:
+			informers[ns] = factory.HTTPTriggers().Informer()
+		case fv1.KubernetesWatchResource:
+			informers[ns] = factory.KubernetesWatchTriggers().Informer()
+		case fv1.MessageQueueResource:
+			informers[ns] = factory.MessageQueueTriggers().Informer()
+		case fv1.PackagesResource:
+			informers[ns] = factory.Packages().Informer()
+		case fv1.TimeTriggerResource:
+			informers[ns] = factory.TimeTriggers().Informer()
+		default:
+			panic("Unknown kind: " + kind)
+		}
+	}
+	return informers
+}
+
 func GetInformerFactoryByReadyPod(client kubernetes.Interface, namespace string, labelSelector *metav1.LabelSelector) (k8sInformers.SharedInformerFactory, error) {
 	informerFactory := k8sInformers.NewSharedInformerFactoryWithOptions(client, 0,
 		k8sInformers.WithNamespace(namespace),