pkg/k8sutil: add new NewClientset function

This commit adds NewClientset exported function, which allows creating
Kubernetes Clientset from content of kubeconfig file, which allows to
create it from sources differant than file on local file system.

This is required for being able to execute 'lokoctl health' without
having kubeconfig file present in local assets directory, as it can be
pulled from other places, e.g. Terraform state.

See #608 for more details.

Signed-off-by: Mateusz Gozdek <mateusz@kinvolk.io>

pkg/k8sutil/client.go

@@ -15,6 +15,8 @@
 package k8sutil
 
 import (
+	"fmt"
+
 	"k8s.io/client-go/kubernetes"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/oidc"
 	"k8s.io/client-go/tools/clientcmd"
@@ -35,3 +37,19 @@ func NewClientsetFromFile(kubeconfigPath string) (*kubernetes.Clientset, error)
 
 	return apiclientset, nil
 }
+
+// NewClientset creates new Kubernetes Client set object from given kubeconfig
+// file content.
+func NewClientset(data []byte) (*kubernetes.Clientset, error) {
+	c, err := clientcmd.NewClientConfigFromBytes(data)
+	if err != nil {
+		return nil, fmt.Errorf("creating client config failed: %w", err)
+	}
+
+	restConfig, err := c.ClientConfig()
+	if err != nil {
+		return nil, fmt.Errorf("converting client config to rest client config failed: %w", err)
+	}
+
+	return kubernetes.NewForConfig(restConfig)
+}

pkg/k8sutil/client_test.go

@@ -0,0 +1,54 @@
+// Copyright 2020 The Lokomotive Authors
+//
+// 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 k8sutil_test
+
+import (
+	"testing"
+
+	"github.com/kinvolk/lokomotive/pkg/k8sutil"
+)
+
+const (
+	validKubeconfig = `
+apiVersion: v1
+kind: Config
+clusters:
+- name: admin
+  cluster:
+    server: https://nonexistent:6443
+users:
+- name: admin
+  user:
+    token: "foo.bar"
+current-context: admin
+contexts:
+- name: admin
+  context:
+    cluster: admin
+    user: admin
+`
+)
+
+func TestNewClientset(t *testing.T) {
+	if _, err := k8sutil.NewClientset([]byte(validKubeconfig)); err != nil {
+		t.Fatalf("Creating clientset from valid kubeconfig should succeed, got: %v", err)
+	}
+}
+
+func TestNewClientsetInvalidKubeconfig(t *testing.T) {
+	if _, err := k8sutil.NewClientset([]byte("foo")); err == nil {
+		t.Fatalf("Creating clientset from invalid kubeconfig should fail")
+	}
+}