Initial package

knabben · Feb 3, 2022 · c315f4b · c315f4b
1 parent 38e1b87
commit c315f4b
Showing 1 changed file with 191 additions and 0 deletions.
diff --git a/main.go b/main.go
@@ -0,0 +1,191 @@
+package main
+
+import (
+	"bytes"
+	"context"
+	"flag"
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/goccy/go-graphviz"
+	"github.com/goccy/go-graphviz/cgraph"
+	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/restmapper"
+
+	"k8s.io/apimachinery/pkg/api/meta"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/client-go/dynamic"
+	"k8s.io/client-go/tools/clientcmd"
+)
+
+var (
+	kubeconfig *string
+
+	group    *string
+	version  *string
+	resource *string
+
+	name      *string
+	namespace *string
+)
+
+type Graphz struct {
+	client dynamic.Interface
+	mapper meta.RESTMapper
+	graph  *cgraph.Graph
+}
+
+func init() {
+	kubeconfig = flag.String("kubeconfig", "kubeconfig", "(optional) absolute path to the kubeconfig file")
+
+	// object GVR flags
+	group = flag.String("group", "", "Group of the object")
+	version = flag.String("version", "v1", "Version of the object")
+	resource = flag.String("resource", "pods", "Resource of the object")
+
+	// object details flags
+	name = flag.String("name", "coredns", "Name of the object")
+	namespace = flag.String("namespace", "default", "Namespace of the object")
+}
+
+// fetchOnwerReferences return the references to the owners of a particular object
+func (g *Graphz) fetchOnwerReferences(group, version, resource, namespace, name string) ([]interface{}, error) {
+	scheme := schema.GroupVersionResource{Group: group, Version: version, Resource: resource}
+	res, err := g.client.Resource(scheme).Namespace(namespace).Get(context.TODO(), name, metav1.GetOptions{})
+	if err != nil {
+		return nil, err
+	}
+
+	metadata, exists, err := unstructured.NestedMap(res.Object, "metadata")
+	if err != nil && !exists {
+		panic(err)
+	}
+
+	owners := metadata["ownerReferences"]
+	if owners != nil { // typecase on owners existence
+		return owners.([]interface{}), nil
+	}
+	return nil, nil
+}
+
+// fetchRecursiveOwners traverse with bfs and create edges between nodes
+func (g *Graphz) fetchRecursiveOwners(owners []interface{}, node *cgraph.Node) {
+	for _, n := range owners {
+		owner := n.(map[string]interface{})
+
+		apiVersion := owner["apiVersion"].(string)
+		avSplit := strings.Split(apiVersion, "/")
+		ownerKind := owner["kind"].(string)
+		ownerName := owner["name"].(string)
+
+		// create owner node
+		gnode, err := g.graph.CreateNode(generateNodeName(ownerName, apiVersion, ownerKind))
+		if err != nil {
+			panic(err.Error())
+		}
+
+		// create owner node and node edge
+		_, err = g.graph.CreateEdge("", node, gnode)
+		if err != nil {
+			panic(err.Error())
+		}
+
+		// convert GVK to GVR, so it's possible to fetch object owners
+		gk := schema.ParseGroupKind(fmt.Sprintf("%s.%s", ownerKind, avSplit[0]))
+		mapping, err := g.mapper.RESTMapping(gk)
+		if err != nil {
+			panic(err)
+		}
+
+		owners, err := g.fetchOnwerReferences(mapping.Resource.Group, mapping.Resource.Version, mapping.Resource.Resource, *namespace, ownerName)
+		if err != nil {
+			panic(err.Error())
+		}
+		if owners != nil {
+			g.fetchRecursiveOwners(owners, gnode)
+		}
+	}
+}
+
+// NewClients return dynamic and discovery clients
+func NewClients(kubeconfig *string) (*discovery.DiscoveryClient, dynamic.Interface, error) {
+	// use the current context in kubeconfig
+	config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	client, err := dynamic.NewForConfig(config)
+	if err != nil {
+		return nil, nil, err
+	}
+
+	return discovery.NewDiscoveryClientForConfigOrDie(config), client, nil
+}
+
+// generateNodeName return GRV/GRK formatted name
+func generateNodeName(name, group, resource string) string {
+	return fmt.Sprintf("%s\n%s\n%s", resource, group, name)
+}
+
+func main() {
+	var (
+		owners []interface{}
+		buf    bytes.Buffer
+	)
+
+	flag.Parse()
+
+	// create graphviz setup
+	g := graphviz.New()
+	graph, err := g.Graph()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	defer func() {
+		if err := graph.Close(); err != nil {
+			log.Fatal(err)
+		}
+		g.Close()
+	}()
+
+	// return discovery and dynamic clients
+	discovery, client, err := NewClients(kubeconfig)
+	if err != nil {
+		panic(err.Error())
+	}
+
+	// setup initial mapper from gvr -> gvk
+	groupResources, err := restmapper.GetAPIGroupResources(discovery)
+	if err != nil {
+		panic(err.Error())
+	}
+	mapper := restmapper.NewDiscoveryRESTMapper(groupResources)
+
+	// add initial node from passed parameter
+	gz := &Graphz{
+		client: client,
+		mapper: mapper,
+		graph:  graph,
+	}
+	node, err := graph.CreateNode(generateNodeName(*name, *group, *resource))
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// fetch initial parent owners of the object
+	if owners, err = gz.fetchOnwerReferences(*group, *version, *resource, *namespace, *name); err != nil {
+		panic(err.Error())
+	}
+	gz.fetchRecursiveOwners(owners, node)
+
+	// print out diagram
+	if err := g.Render(graph, "dot", &buf); err != nil {
+		log.Fatalf("%+v", err)
+	}
+	fmt.Println(buf.String())
+}