Adding initial version of Kubernetes backend (#552)

Co-authored-by: laszlocph <laszlo@laszlo.cloud>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: Rynoxx <rynoxx@grid-servers.net>

pipeline/backend/kubernetes/utils.go

@@ -0,0 +1,53 @@
+package kubernetes
+
+import (
+	"os"
+	"strings"
+
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/client-go/kubernetes"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/tools/clientcmd"
+)
+
+func dnsName(i string) string {
+	return strings.Replace(i, "_", "-", -1)
+}
+
+func isImagePullBackOffState(pod *v1.Pod) bool {
+	for _, containerState := range pod.Status.ContainerStatuses {
+		if containerState.State.Waiting != nil {
+			if containerState.State.Waiting.Reason == "ImagePullBackOff" {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// getClientOutOfCluster returns a k8s clientset to the request from outside of cluster
+func getClientOutOfCluster() (kubernetes.Interface, error) {
+	kubeconfigPath := os.Getenv("KUBECONFIG")
+	if kubeconfigPath == "" {
+		kubeconfigPath = os.Getenv("HOME") + "/.kube/config"
+	}
+
+	// use the current context in kubeconfig
+	config, err := clientcmd.BuildConfigFromFlags("", kubeconfigPath)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	return kubernetes.NewForConfig(config)
+}
+
+// getClient returns a k8s clientset to the request from inside of cluster
+func getClientInsideOfCluster() (kubernetes.Interface, error) {
+	config, err := rest.InClusterConfig()
+	if err != nil {
+		return nil, err
+	}
+
+	return kubernetes.NewForConfig(config)
+}