util: NewK8sClient() should not panic on non-Kubernetes clusters

When NewK8sClient() detects and error, it used to call FatalLogMsg()
which causes a panic. There are additional features that can be used on
Kubernetes clusters, but these are not a requirement for most
functionalities of the driver.

Instead of causing a panic, returning an error should suffice. This
allows using the driver on non-Kubernetes clusters again.

Fixes: #2452
Signed-off-by: Niels de Vos <ndevos@redhat.com>
(cherry picked from commit 60c2afb)

internal/rbd/rbd_healer.go

@@ -125,7 +125,13 @@ func callNodeStageVolume(ns *NodeServer, c *k8s.Clientset, pv *v1.PersistentVolu
 
 // runVolumeHealer heal the volumes attached on a node.
 func runVolumeHealer(ns *NodeServer, conf *util.Config) error {
-	c := util.NewK8sClient()
+	c, err := util.NewK8sClient()
+	if err != nil {
+		util.ErrorLogMsg("failed to connect to Kubernetes: %v", err)
+
+		return err
+	}
+
 	val, err := c.StorageV1().VolumeAttachments().List(context.TODO(), metav1.ListOptions{})
 	if err != nil {
 		util.ErrorLogMsg("list volumeAttachments failed, err: %v", err)

internal/rbd/rbd_util.go

@@ -1060,7 +1060,11 @@ func genVolFromVolID(
 	// be the same in the PV.Spec.CSI.VolumeHandle. Check the PV annotation for
 	// the new volumeHandle. If the new volumeHandle is found, generate the RBD
 	// volume structure from the new volumeHandle.
-	c := util.NewK8sClient()
+	c, cErr := util.NewK8sClient()
+	if cErr != nil {
+		return vol, cErr
+	}
+
 	listOpt := metav1.ListOptions{
 		LabelSelector: PVReplicatedLabelKey,
 	}

internal/util/aws_metadata.go

@@ -123,7 +123,12 @@ func initAWSMetadataKMS(args KMSInitializerArgs) (EncryptionKMS, error) {
 }
 
 func (kms *AWSMetadataKMS) getSecrets() (map[string]interface{}, error) {
-	c := NewK8sClient()
+	c, err := NewK8sClient()
+	if err != nil {
+		return nil, fmt.Errorf("failed to connect to Kubernetes to "+
+			"get Secret %s/%s: %w", kms.namespace, kms.secretName, err)
+	}
+
 	secret, err := c.CoreV1().Secrets(kms.namespace).Get(context.TODO(),
 		kms.secretName, metav1.GetOptions{})
 	if err != nil {

internal/util/k8s.go

@@ -17,33 +17,34 @@ limitations under the License.
 package util
 
 import (
+	"fmt"
 	"os"
 
-	k8s "k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/kubernetes"
 	"k8s.io/client-go/rest"
 	"k8s.io/client-go/tools/clientcmd"
 )
 
 // NewK8sClient create kubernetes client.
-func NewK8sClient() *k8s.Clientset {
+func NewK8sClient() (*kubernetes.Clientset, error) {
 	var cfg *rest.Config
 	var err error
 	cPath := os.Getenv("KUBERNETES_CONFIG_PATH")
 	if cPath != "" {
 		cfg, err = clientcmd.BuildConfigFromFlags("", cPath)
 		if err != nil {
-			FatalLogMsg("Failed to get cluster config with error: %v\n", err)
+			return nil, fmt.Errorf("failed to get cluster config from %q: %w", cPath, err)
 		}
 	} else {
 		cfg, err = rest.InClusterConfig()
 		if err != nil {
-			FatalLogMsg("Failed to get cluster config with error: %v\n", err)
+			return nil, fmt.Errorf("failed to get cluster config: %w", err)
 		}
 	}
-	client, err := k8s.NewForConfig(cfg)
+	client, err := kubernetes.NewForConfig(cfg)
 	if err != nil {
-		FatalLogMsg("Failed to create client with error: %v\n", err)
+		return nil, fmt.Errorf("failed to create client: %w", err)
 	}
 
-	return client
+	return client, nil
 }

internal/util/kms.go

@@ -146,7 +146,12 @@ func getKMSConfigMap() (map[string]interface{}, error) {
 	}
 	cmName := getKMSConfigMapName()
 
-	c := NewK8sClient()
+	c, err := NewK8sClient()
+	if err != nil {
+		return nil, fmt.Errorf("can not get ConfigMap %q, failed to "+
+			"connect to Kubernetes: %w", cmName, err)
+	}
+
 	cm, err := c.CoreV1().ConfigMaps(ns).Get(context.Background(),
 		cmName, metav1.GetOptions{})
 	if err != nil {

internal/util/secretskms.go

@@ -155,7 +155,12 @@ func (kms SecretsMetadataKMS) fetchEncryptionPassphrase(
 		secretNamespace = defaultNamespace
 	}
 
-	c := NewK8sClient()
+	c, err := NewK8sClient()
+	if err != nil {
+		return "", fmt.Errorf("can not get Secret %s/%s, failed to "+
+			"connect to Kubernetes: %w", secretNamespace, secretName, err)
+	}
+
 	secret, err := c.CoreV1().Secrets(secretNamespace).Get(context.TODO(),
 		secretName, metav1.GetOptions{})
 	if err != nil {

internal/util/topology.go

@@ -32,7 +32,12 @@ const (
 )
 
 func k8sGetNodeLabels(nodeName string) (map[string]string, error) {
-	client := NewK8sClient()
+	client, err := NewK8sClient()
+	if err != nil {
+		return nil, fmt.Errorf("can not get node %q information, failed "+
+			"to connect to Kubernetes: %w", nodeName, err)
+	}
+
 	node, err := client.CoreV1().Nodes().Get(context.TODO(), nodeName, metav1.GetOptions{})
 	if err != nil {
 		return nil, fmt.Errorf("failed to get node %q information: %w", nodeName, err)

internal/util/vault_sa.go

@@ -260,7 +260,12 @@ func (kms *VaultTenantSA) setServiceAccountName(config map[string]interface{}) e
 // getServiceAccount returns the Tenants ServiceAccount with the name
 // configured in the VaultTenantSA.
 func (kms *VaultTenantSA) getServiceAccount() (*corev1.ServiceAccount, error) {
-	c := kms.getK8sClient()
+	c, err := kms.getK8sClient()
+	if err != nil {
+		return nil, fmt.Errorf("can not get ServiceAccount %s/%s, "+
+			"failed to connect to Kubernetes: %w", kms.Tenant, kms.tenantSAName, err)
+	}
+
 	sa, err := c.CoreV1().ServiceAccounts(kms.Tenant).Get(context.TODO(),
 		kms.tenantSAName, metav1.GetOptions{})
 	if err != nil {
@@ -279,7 +284,13 @@ func (kms *VaultTenantSA) getToken() (string, error) {
 		return "", err
 	}
 
-	c := kms.getK8sClient()
+	c, err := kms.getK8sClient()
+	if err != nil {
+		return "", fmt.Errorf("can not get ServiceAccount %s/%s, failed "+
+			"to connect to Kubernetes: %w", kms.Tenant,
+			kms.tenantSAName, err)
+	}
+
 	for _, secretRef := range sa.Secrets {
 		secret, err := c.CoreV1().Secrets(kms.Tenant).Get(context.TODO(), secretRef.Name, metav1.GetOptions{})
 		if err != nil {

internal/util/vault_tokens.go

@@ -433,12 +433,16 @@ func (vtc *vaultTenantConnection) initCertificates(config map[string]interface{}
 	return nil
 }
 
-func (vtc *vaultTenantConnection) getK8sClient() *kubernetes.Clientset {
+func (vtc *vaultTenantConnection) getK8sClient() (*kubernetes.Clientset, error) {
 	if vtc.client == nil {
-		vtc.client = NewK8sClient()
+		client, err := NewK8sClient()
+		if err != nil {
+			return nil, err
+		}
+		vtc.client = client
 	}
 
-	return vtc.client
+	return vtc.client, nil
 }
 
 // FetchDEK returns passphrase from Vault. The passphrase is stored in a
@@ -488,7 +492,11 @@ func (vtc *vaultTenantConnection) RemoveDEK(key string) error {
 }
 
 func (kms *VaultTokensKMS) getToken() (string, error) {
-	c := kms.getK8sClient()
+	c, err := kms.getK8sClient()
+	if err != nil {
+		return "", err
+	}
+
 	secret, err := c.CoreV1().Secrets(kms.Tenant).Get(context.TODO(), kms.TokenName, metav1.GetOptions{})
 	if err != nil {
 		return "", err
@@ -503,7 +511,11 @@ func (kms *VaultTokensKMS) getToken() (string, error) {
 }
 
 func (vtc *vaultTenantConnection) getCertificate(tenant, secretName, key string) (string, error) {
-	c := vtc.getK8sClient()
+	c, err := vtc.getK8sClient()
+	if err != nil {
+		return "", err
+	}
+
 	secret, err := c.CoreV1().Secrets(tenant).Get(context.TODO(), secretName, metav1.GetOptions{})
 	if err != nil {
 		return "", err
@@ -545,7 +557,11 @@ func (vtc *vaultTenantConnection) parseTenantConfig() (map[string]interface{}, e
 	}
 
 	// fetch the ConfigMap from the tenants namespace
-	c := vtc.getK8sClient()
+	c, err := vtc.getK8sClient()
+	if err != nil {
+		return nil, err
+	}
+
 	cm, err := c.CoreV1().ConfigMaps(vtc.Tenant).Get(context.TODO(),
 		vtc.ConfigName, metav1.GetOptions{})
 	if apierrs.IsNotFound(err) {