fix(backend): Allow initializing the Kubernetes client with a kubeconfig

backend/src/apiserver/client/argo.go

@@ -23,7 +23,6 @@ import (
 	"github.com/golang/glog"
 	"github.com/kubeflow/pipelines/backend/src/common/util"
 	"github.com/pkg/errors"
-	"k8s.io/client-go/rest"
 )
 
 type ArgoClientInterface interface {
@@ -41,7 +40,7 @@ func (argoClient *ArgoClient) Workflow(namespace string) argoprojv1alpha1.Workfl
 func NewArgoClientOrFatal(initConnectionTimeout time.Duration, clientParams util.ClientParameters) *ArgoClient {
 	var argoProjClient argoprojv1alpha1.ArgoprojV1alpha1Interface
 	operation := func() error {
-		restConfig, err := rest.InClusterConfig()
+		restConfig, err := util.GetKubernetesConfig()
 		if err != nil {
 			return errors.Wrap(err, "Failed to initialize the RestConfig")
 		}

backend/src/apiserver/client/swf.go

@@ -25,7 +25,6 @@ import (
 	swfclient "github.com/kubeflow/pipelines/backend/src/crd/pkg/client/clientset/versioned"
 	"github.com/kubeflow/pipelines/backend/src/crd/pkg/client/clientset/versioned/typed/scheduledworkflow/v1beta1"
 	"github.com/pkg/errors"
-	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 	"k8s.io/client-go/util/homedir"
 )
@@ -46,7 +45,7 @@ func (swfClient *SwfClient) ScheduledWorkflow(namespace string) v1beta1.Schedule
 func NewScheduledWorkflowClientOrFatal(initConnectionTimeout time.Duration, clientParams util.ClientParameters) *SwfClient {
 	var swfClient v1beta1.ScheduledworkflowV1beta1Interface
 	operation := func() error {
-		restConfig, err := rest.InClusterConfig()
+		restConfig, err := util.GetKubernetesConfig()
 		if err != nil {
 			return err
 		}

backend/src/apiserver/client/util.go

@@ -15,15 +15,15 @@
 package client
 
 import (
+	"os"
+
 	"github.com/kubeflow/pipelines/backend/src/common/util"
 	"github.com/pkg/errors"
 	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/rest"
-	"os"
 )
 
 func getKubernetesClientset(clientParams util.ClientParameters) (*kubernetes.Clientset, error) {
-	restConfig, err := rest.InClusterConfig()
+	restConfig, err := util.GetKubernetesConfig()
 	if err != nil {
 		return nil, errors.Wrap(err, "Failed to initialize kubernetes client")
 	}

backend/src/cache/client/kubernetes_core.go

@@ -9,7 +9,6 @@ import (
 	"github.com/pkg/errors"
 	"k8s.io/client-go/kubernetes"
 	v1 "k8s.io/client-go/kubernetes/typed/core/v1"
-	"k8s.io/client-go/rest"
 )
 
 type KubernetesCoreInterface interface {
@@ -25,7 +24,7 @@ func (c *KubernetesCore) PodClient(namespace string) v1.PodInterface {
 }
 
 func createKubernetesCore(clientParams util.ClientParameters) (KubernetesCoreInterface, error) {
-	restConfig, err := rest.InClusterConfig()
+	restConfig, err := util.GetKubernetesConfig()
 	if err != nil {
 		return nil, errors.Wrap(err, "Failed to initialize kubernetes client.")
 	}

backend/src/common/util/execution_client.go

@@ -28,7 +28,6 @@ import (
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/labels"
 	"k8s.io/apimachinery/pkg/types"
-	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/cache"
 )
 
@@ -87,7 +86,7 @@ func NewExecutionClientOrFatal(execType ExecutionType, initConnectionTimeout tim
 	case ArgoWorkflow:
 		var argoProjClient *argoclient.Clientset
 		operation := func() error {
-			restConfig, err := rest.InClusterConfig()
+			restConfig, err := GetKubernetesConfig()
 			if err != nil {
 				return errors.Wrap(err, "Failed to initialize the RestConfig")
 			}
@@ -106,8 +105,8 @@ func NewExecutionClientOrFatal(execType ExecutionType, initConnectionTimeout tim
 		return &WorkflowClient{client: argoProjClient}
 	case TektonPipelineRun:
 		var prClient *prclientset.Clientset
-		var operation = func() error {
-			restConfig, err := rest.InClusterConfig()
+		operation := func() error {
+			restConfig, err := GetKubernetesConfig()
 			if err != nil {
 				return errors.Wrap(err, "Failed to initialize the RestConfig")
 			}
@@ -139,7 +138,7 @@ func NewExecutionInformerOrFatal(execType ExecutionType, namespace string,
 	case ArgoWorkflow:
 		var argoInformer argoinformer.SharedInformerFactory
 		operation := func() error {
-			restConfig, err := rest.InClusterConfig()
+			restConfig, err := GetKubernetesConfig()
 			if err != nil {
 				return errors.Wrap(err, "Failed to initialize the RestConfig")
 			}
@@ -167,8 +166,8 @@ func NewExecutionInformerOrFatal(execType ExecutionType, namespace string,
 	case TektonPipelineRun:
 		var prInformer prinformer.SharedInformerFactory
 		var prClient *prclientset.Clientset
-		var operation = func() error {
-			restConfig, err := rest.InClusterConfig()
+		operation := func() error {
+			restConfig, err := GetKubernetesConfig()
 			if err != nil {
 				return errors.Wrap(err, "Failed to initialize the RestConfig")
 			}

backend/src/common/util/service.go

@@ -50,6 +50,26 @@ func WaitForAPIAvailable(initializeTimeout time.Duration, basePath string, apiAd
 	return errors.Wrapf(err, "Waiting for ml pipeline API server failed after all attempts.")
 }
 
+// GetKubernetesConfig will first try an in-cluster configuration but fallback to using a kubeconfig.
+func GetKubernetesConfig() (*rest.Config, error) {
+	restConfig, errInCluster := rest.InClusterConfig()
+	if errInCluster == nil {
+		return restConfig, nil
+	}
+
+	// Fallback to using a kubeconfig
+	clientConfig := clientcmd.NewNonInteractiveDeferredLoadingClientConfig(
+		clientcmd.NewDefaultClientConfigLoadingRules(), &clientcmd.ConfigOverrides{},
+	)
+
+	restConfig, errKubeconfig := clientConfig.ClientConfig()
+	if errKubeconfig != nil {
+		return nil, fmt.Errorf("%w; %w", errInCluster, errKubeconfig)
+	}
+
+	return restConfig, nil
+}
+
 func GetKubernetesClientFromClientConfig(clientConfig clientcmd.ClientConfig) (
 	*kubernetes.Clientset, *rest.Config, string, error,
 ) {

backend/src/v2/driver/driver.go

@@ -21,6 +21,7 @@ import (
 	"strconv"
 	"time"
 
+	"github.com/kubeflow/pipelines/backend/src/common/util"
 	"github.com/kubeflow/pipelines/backend/src/v2/objectstore"
 
 	"github.com/golang/glog"
@@ -41,7 +42,6 @@ import (
 	k8sres "k8s.io/apimachinery/pkg/api/resource"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/client-go/kubernetes"
-	"k8s.io/client-go/rest"
 )
 
 var dummyImages = map[string]string{
@@ -136,7 +136,7 @@ func RootDAG(ctx context.Context, opts Options, mlmd *metadata.Client) (executio
 	// TODO(v2): in pipeline spec, rename GCS output directory to pipeline root.
 	pipelineRoot := opts.RuntimeConfig.GetGcsOutputDirectory()
 
-	restConfig, err := rest.InClusterConfig()
+	restConfig, err := util.GetKubernetesConfig()
 	if err != nil {
 		return nil, fmt.Errorf("failed to initialize kubernetes client: %w", err)
 	}
@@ -1922,7 +1922,7 @@ func deletePVC(
 
 func createK8sClient() (*kubernetes.Clientset, error) {
 	// Initialize Kubernetes client set
-	restConfig, err := rest.InClusterConfig()
+	restConfig, err := util.GetKubernetesConfig()
 	if err != nil {
 		return nil, fmt.Errorf("failed to initialize kubernetes client: %w", err)
 	}