Allow empty namespace for fission function and builder (#2621)

Currently, we create Fission resources in the default namespace, function-related resources are created in the fission-function namespace, whereas builder resources are created in the fission-builder namespace. This causes confusion for a lot of users.
In this fix, we allow the user to set the function and builder namespace empty so that function and builder resources are created in the same namespace as the function resource always.

If the user desires older behaviour they can functionNamespace and builderNamespace the same previous before the upgrade.

* use default namespace for fission  function and builder
* support for existing fission namespaces
* Replace builder and function namespace with template
* Fix namespace creation template

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

pkg/buildermgr/pkgwatcher.go

@@ -37,29 +37,29 @@ import (
 
 type (
 	packageWatcher struct {
-		logger           *zap.Logger
-		fissionClient    versioned.Interface
-		k8sClient        kubernetes.Interface
-		podInformer      k8sCache.SharedIndexInformer
-		pkgInformer      map[string]k8sCache.SharedIndexInformer
-		builderNamespace string
-		storageSvcUrl    string
-		buildCache       *cache.Cache
+		logger        *zap.Logger
+		fissionClient versioned.Interface
+		nsResolver    *utils.NamespaceResolver
+		k8sClient     kubernetes.Interface
+		podInformer   k8sCache.SharedIndexInformer
+		pkgInformer   map[string]k8sCache.SharedIndexInformer
+		storageSvcUrl string
+		buildCache    *cache.Cache
 	}
 )
 
 func makePackageWatcher(logger *zap.Logger, fissionClient versioned.Interface, k8sClientSet kubernetes.Interface,
-	builderNamespace string, storageSvcUrl string, podInformer k8sCache.SharedIndexInformer,
+	storageSvcUrl string, podInformer k8sCache.SharedIndexInformer,
 	pkgInformer map[string]k8sCache.SharedIndexInformer) *packageWatcher {
 	pkgw := &packageWatcher{
-		logger:           logger.Named("package_watcher"),
-		fissionClient:    fissionClient,
-		k8sClient:        k8sClientSet,
-		podInformer:      podInformer,
-		pkgInformer:      pkgInformer,
-		builderNamespace: builderNamespace,
-		storageSvcUrl:    storageSvcUrl,
-		buildCache:       cache.MakeCache(0, 0),
+		logger:        logger.Named("package_watcher"),
+		fissionClient: fissionClient,
+		k8sClient:     k8sClientSet,
+		nsResolver:    utils.DefaultNSResolver(),
+		podInformer:   podInformer,
+		pkgInformer:   pkgInformer,
+		storageSvcUrl: storageSvcUrl,
+		buildCache:    cache.MakeCache(0, 0),
 	}
 	return pkgw
 }
@@ -137,12 +137,7 @@ func (pkgw *packageWatcher) build(ctx context.Context, srcpkg *fv1.Package) {
 		for _, item := range items {
 			pod := item.(*apiv1.Pod)
 
-			// In order to support backward compatibility, for all builder images created in default env,
-			// the pods will be created in fission-builder namespace
-			builderNs := pkgw.builderNamespace
-			if env.ObjectMeta.Namespace != metav1.NamespaceDefault {
-				builderNs = env.ObjectMeta.Namespace
-			}
+			builderNs := pkgw.nsResolver.GetBuilderNS(env.ObjectMeta.Namespace)
 
 			// Filter non-matching pods
 			if pod.ObjectMeta.Labels[LABEL_ENV_NAME] != env.ObjectMeta.Name ||