Plugin code refactoring

The plugin code has been refactored to
implement a common interface.
This will allow us to do plugin validation
at loadtime of the plugin instead of at runtime.
This also makes the code calling the plugins cleaner
and easier to read.

Issue-ID: MULTICLOUD-557
Change-Id: Ice2bcc9b850d7c0e1707dcc42132c63dd77472a7
Signed-off-by: Kiran Kamineni <kiran.k.kamineni@intel.com>

3 files changed, 127 insertions, 148 deletions

diff --git a/src/k8splugin/internal/app/client.go b/src/k8splugin/internal/app/client.go
index 158d21de..9a5aa9e9 100644
--- a/src/k8splugin/internal/app/client.go
+++ b/src/k8splugin/internal/app/client.go
@@ -16,15 +16,16 @@ package app
 import (
 	"log"
 	"os"
-	"strings"
+	"time"
 
-	utils "k8splugin/internal"
 	"k8splugin/internal/config"
 	"k8splugin/internal/connection"
 	"k8splugin/internal/helm"
+	"k8splugin/internal/plugin"
 
 	pkgerrors "github.com/pkg/errors"
 	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/client-go/discovery"
 	"k8s.io/client-go/dynamic"
 	"k8s.io/client-go/kubernetes"
@@ -32,16 +33,12 @@ import (
 	"k8s.io/client-go/tools/clientcmd"
 )
 
-// PluginReference is the interface that is implemented
-type PluginReference interface {
-	Create(yamlFilePath string, namespace string, client *KubernetesClient) (string, error)
-	Delete(resource helm.KubernetesResource, namespace string, client *KubernetesClient) error
-}
-
+// KubernetesClient encapsulates the different clients' interfaces
+// we need when interacting with a Kubernetes cluster
 type KubernetesClient struct {
-	clientSet      *kubernetes.Clientset
+	clientSet      kubernetes.Interface
 	dynamicClient  dynamic.Interface
-	discoverClient *discovery.DiscoveryClient
+	discoverClient discovery.CachedDiscoveryInterface
 	restMapper     meta.RESTMapper
 }
 
@@ -86,40 +83,35 @@ func (k *KubernetesClient) init(cloudregion string) error {
 		return pkgerrors.Wrap(err, "Creating dynamic client")
 	}
 
-	k.discoverClient, err = discovery.NewDiscoveryClientForConfig(config)
+	k.discoverClient, err = discovery.NewCachedDiscoveryClientForConfig(config, os.TempDir(), "", 10*time.Minute)
 	if err != nil {
 		return pkgerrors.Wrap(err, "Creating discovery client")
 	}
 
+	k.restMapper = restmapper.NewDeferredDiscoveryRESTMapper(k.discoverClient)
 	return nil
 }
 
 func (k *KubernetesClient) ensureNamespace(namespace string) error {
-	namespacePlugin, ok := utils.LoadedPlugins["namespace"]
-	if !ok {
-		return pkgerrors.New("No plugin for namespace resource found")
-	}
 
-	symGetNamespaceFunc, err := namespacePlugin.Lookup("Get")
+	pluginImpl, err := plugin.GetPluginByKind("Namespace")
 	if err != nil {
-		return pkgerrors.Wrap(err, "Error fetching get namespace function")
+		return pkgerrors.Wrap(err, "Loading Namespace Plugin")
 	}
 
-	ns, _ := symGetNamespaceFunc.(func(string, string, kubernetes.Interface) (string, error))(
-		namespace, namespace, k.clientSet)
+	ns, err := pluginImpl.Get(helm.KubernetesResource{
+		Name: namespace,
+		GVK: schema.GroupVersionKind{
+			Group:   "",
+			Version: "v1",
+			Kind:    "Namespace",
+		},
+	}, namespace, k)
 
 	if ns == "" {
 		log.Println("Creating " + namespace + " namespace")
-		symGetNamespaceFunc, err := namespacePlugin.Lookup("Create")
-		if err != nil {
-			return pkgerrors.Wrap(err, "Error fetching create namespace plugin")
-		}
-		namespaceResource := &utils.ResourceData{
-			Namespace: namespace,
-		}
 
-		_, err = symGetNamespaceFunc.(func(*utils.ResourceData, kubernetes.Interface) (string, error))(
-			namespaceResource, k.clientSet)
+		_, err = pluginImpl.Create("", namespace, k)
 		if err != nil {
 			return pkgerrors.Wrap(err, "Error creating "+namespace+" namespace")
 		}
@@ -127,50 +119,6 @@ func (k *KubernetesClient) ensureNamespace(namespace string) error {
 	return nil
 }
 
-func (k *KubernetesClient) createGeneric(resTempl helm.KubernetesResourceTemplate,
-	namespace string) (helm.KubernetesResource, error) {
-
-	log.Println("Processing Kind: " + resTempl.GVK.Kind)
-
-	//Check if have the mapper before loading the plugin
-	err := k.updateMapper()
-	if err != nil {
-		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "Unable to create RESTMapper")
-	}
-
-	pluginObject, ok := utils.LoadedPlugins["generic"]
-	if !ok {
-		return helm.KubernetesResource{}, pkgerrors.New("No generic plugin found")
-	}
-
-	symbol, err := pluginObject.Lookup("ExportedVariable")
-	if err != nil {
-		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "No ExportedVariable symbol found")
-	}
-
-	//Assert if it implements the PluginReference interface
-	genericPlugin, ok := symbol.(PluginReference)
-	if !ok {
-		return helm.KubernetesResource{}, pkgerrors.New("ExportedVariable is not PluginReference type")
-	}
-
-	if _, err := os.Stat(resTempl.FilePath); os.IsNotExist(err) {
-		return helm.KubernetesResource{}, pkgerrors.New("File " + resTempl.FilePath + "does not exists")
-	}
-
-	log.Println("Processing file: " + resTempl.FilePath)
-
-	name, err := genericPlugin.Create(resTempl.FilePath, namespace, k)
-	if err != nil {
-		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "Error in generic plugin")
-	}
-
-	return helm.KubernetesResource{
-		GVK:  resTempl.GVK,
-		Name: name,
-	}, nil
-}
-
 func (k *KubernetesClient) createKind(resTempl helm.KubernetesResourceTemplate,
 	namespace string) (helm.KubernetesResource, error) {
 
@@ -182,28 +130,16 @@ func (k *KubernetesClient) createKind(resTempl helm.KubernetesResourceTemplate,
 
 	log.Println("Processing file: " + resTempl.FilePath)
 
-	//Populate the namespace from profile instead of instance body
-	genericKubeData := &utils.ResourceData{
-		YamlFilePath: resTempl.FilePath,
-		Namespace:    namespace,
-	}
-
-	typePlugin, ok := utils.LoadedPlugins[strings.ToLower(resTempl.GVK.Kind)]
-	if !ok {
-		log.Println("No plugin for kind " + resTempl.GVK.Kind + " found. Using generic Plugin")
-		return k.createGeneric(resTempl, namespace)
-	}
-
-	symCreateResourceFunc, err := typePlugin.Lookup("Create")
+	pluginImpl, err := plugin.GetPluginByKind(resTempl.GVK.Kind)
 	if err != nil {
-		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "Error fetching "+resTempl.GVK.Kind+" plugin")
+		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "Error loading plugin")
 	}
 
-	createdResourceName, err := symCreateResourceFunc.(func(*utils.ResourceData, kubernetes.Interface) (string, error))(
-		genericKubeData, k.clientSet)
+	createdResourceName, err := pluginImpl.Create(resTempl.FilePath, namespace, k)
 	if err != nil {
 		return helm.KubernetesResource{}, pkgerrors.Wrap(err, "Error in plugin "+resTempl.GVK.Kind+" plugin")
 	}
+
 	log.Print(createdResourceName + " created")
 	return helm.KubernetesResource{
 		GVK:  resTempl.GVK,
@@ -231,58 +167,18 @@ func (k *KubernetesClient) createResources(sortedTemplates []helm.KubernetesReso
 	return createdResources, nil
 }
 
-func (k *KubernetesClient) deleteGeneric(resource helm.KubernetesResource, namespace string) error {
-	log.Println("Deleting Kind: " + resource.GVK.Kind)
-
-	pluginObject, ok := utils.LoadedPlugins["generic"]
-	if !ok {
-		return pkgerrors.New("No generic plugin found")
-	}
-
-	//Check if have the mapper before loading the plugin
-	err := k.updateMapper()
-	if err != nil {
-		return pkgerrors.Wrap(err, "Unable to create RESTMapper")
-	}
-
-	symbol, err := pluginObject.Lookup("ExportedVariable")
-	if err != nil {
-		return pkgerrors.Wrap(err, "No ExportedVariable symbol found")
-	}
-
-	//Assert that it implements the PluginReference interface
-	genericPlugin, ok := symbol.(PluginReference)
-	if !ok {
-		return pkgerrors.New("ExportedVariable is not PluginReference type")
-	}
-
-	err = genericPlugin.Delete(resource, namespace, k)
-	if err != nil {
-		return pkgerrors.Wrap(err, "Error in generic plugin")
-	}
-
-	return nil
-}
-
 func (k *KubernetesClient) deleteKind(resource helm.KubernetesResource, namespace string) error {
 	log.Println("Deleting Kind: " + resource.GVK.Kind)
 
-	typePlugin, ok := utils.LoadedPlugins[strings.ToLower(resource.GVK.Kind)]
-	if !ok {
-		log.Println("No plugin for kind " + resource.GVK.Kind + " found. Using generic Plugin")
-		return k.deleteGeneric(resource, namespace)
-	}
-
-	symDeleteResourceFunc, err := typePlugin.Lookup("Delete")
+	pluginImpl, err := plugin.GetPluginByKind(resource.GVK.Kind)
 	if err != nil {
-		return pkgerrors.Wrap(err, "Error finding Delete symbol in plugin")
+		return pkgerrors.Wrap(err, "Error loading plugin")
 	}
 
 	log.Println("Deleting resource: " + resource.Name)
-	err = symDeleteResourceFunc.(func(string, string, kubernetes.Interface) error)(
-		resource.Name, namespace, k.clientSet)
+	err = pluginImpl.Delete(resource, namespace, k)
 	if err != nil {
-		return pkgerrors.Wrap(err, "Error destroying "+resource.Name)
+		return pkgerrors.Wrap(err, "Error deleting "+resource.Name)
 	}
 
 	return nil
@@ -300,21 +196,6 @@ func (k *KubernetesClient) deleteResources(resources []helm.KubernetesResource,
 	return nil
 }
 
-func (k *KubernetesClient) updateMapper() error {
-	//Create restMapper if not already done
-	if k.restMapper != nil {
-		return nil
-	}
-
-	groupResources, err := restmapper.GetAPIGroupResources(k.discoverClient)
-	if err != nil {
-		return pkgerrors.Wrap(err, "Get GroupResources")
-	}
-
-	k.restMapper = restmapper.NewDiscoveryRESTMapper(groupResources)
-	return nil
-}
-
 //GetMapper returns the RESTMapper that was created for this client
 func (k *KubernetesClient) GetMapper() meta.RESTMapper {
 	return k.restMapper
@@ -325,3 +206,9 @@ func (k *KubernetesClient) GetMapper() meta.RESTMapper {
 func (k *KubernetesClient) GetDynamicClient() dynamic.Interface {
 	return k.dynamicClient
 }
+
+// GetStandardClient returns the standard client that can be used to handle
+// standard kubernetes kinds
+func (k *KubernetesClient) GetStandardClient() kubernetes.Interface {
+	return k.clientSet
+}
diff --git a/src/k8splugin/internal/app/client_test.go b/src/k8splugin/internal/app/client_test.go
index 4bfbcb18..e52aa7f8 100644
--- a/src/k8splugin/internal/app/client_test.go
+++ b/src/k8splugin/internal/app/client_test.go
@@ -42,7 +42,7 @@ func LoadMockPlugins(krdLoadedPlugins map[string]*plugin.Plugin) error {
 	}
 
 	krdLoadedPlugins["namespace"] = mockPlugin
-	krdLoadedPlugins["deployment"] = mockPlugin
+	krdLoadedPlugins["generic"] = mockPlugin
 	krdLoadedPlugins["service"] = mockPlugin
 
 	return nil
diff --git a/src/k8splugin/internal/plugin/helpers.go b/src/k8splugin/internal/plugin/helpers.go
new file mode 100644
index 00000000..efcd18c1
--- /dev/null
+++ b/src/k8splugin/internal/plugin/helpers.go
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2019 Intel Corporation, Inc
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package plugin
+
+import (
+	"log"
+	"strings"
+
+	utils "k8splugin/internal"
+	"k8splugin/internal/helm"
+
+	pkgerrors "github.com/pkg/errors"
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/kubernetes"
+)
+
+// KubernetesConnector is an interface that is expected to be implemented
+// by any code that calls the plugin framework functions.
+// It implements methods that are needed by the plugins to get Kubernetes
+// clients and other information needed to interface with Kubernetes
+type KubernetesConnector interface {
+	//GetMapper returns the RESTMapper that was created for this client
+	GetMapper() meta.RESTMapper
+
+	//GetDynamicClient returns the dynamic client that is needed for
+	//unstructured REST calls to the apiserver
+	GetDynamicClient() dynamic.Interface
+
+	// GetStandardClient returns the standard client that can be used to handle
+	// standard kubernetes kinds
+	GetStandardClient() kubernetes.Interface
+}
+
+// Reference is the interface that is implemented
+type Reference interface {
+	//Create a kubernetes resource described by the yaml in yamlFilePath
+	Create(yamlFilePath string, namespace string, client KubernetesConnector) (string, error)
+
+	//Get a kubernetes resource based on the groupVersionKind and resourceName provided in resource
+	Get(resource helm.KubernetesResource, namespace string, client KubernetesConnector) (string, error)
+
+	//List all resources of the specified GroupVersionKind in the given namespace
+	//If gvk is empty, the plugin will return all supported objects in the namespace
+	List(gvk schema.GroupVersionKind, namespace string, client KubernetesConnector) ([]helm.KubernetesResource, error)
+
+	//Delete a kubernetes resource described in the provided namespace
+	Delete(resource helm.KubernetesResource, namespace string, client KubernetesConnector) error
+}
+
+// GetPluginByKind returns a plugin by the kind name
+// If plugin does not exist, it will return the generic plugin
+// TODO: Change this once we have a plugin registration mechanism
+func GetPluginByKind(kind string) (Reference, error) {
+
+	typePlugin, ok := utils.LoadedPlugins[strings.ToLower(kind)]
+	if !ok {
+		log.Println("No plugin for kind " + kind + " found. Using generic Plugin")
+		typePlugin, ok = utils.LoadedPlugins["generic"]
+		if !ok {
+			return nil, pkgerrors.New("No generic plugin found")
+		}
+	}
+
+	symbol, err := typePlugin.Lookup("ExportedVariable")
+	if err != nil {
+		return nil, pkgerrors.Wrap(err, "No ExportedVariable symbol found")
+	}
+
+	//Assert if it implements the PluginReference interface
+	pluginImpl, ok := symbol.(Reference)
+	if !ok {
+		return nil, pkgerrors.New("ExportedVariable does not implement plugins.Reference interface type")
+	}
+
+	return pluginImpl, nil
+}