Only start datagatherer if its API resource is available

Signed-off-by: Richard Wall <richard.wall@venafi.com>

pkg/agent/run.go

@@ -24,7 +24,9 @@ import (
 	corev1 "k8s.io/api/core/v1"
 	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
 	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/apimachinery/pkg/util/sets"
 	"k8s.io/client-go/kubernetes"
 	clientgocorev1 "k8s.io/client-go/kubernetes/typed/core/v1"
 	"k8s.io/client-go/tools/record"
@@ -161,11 +163,44 @@ func Run(cmd *cobra.Command, args []string) (returnErr error) {
 	if err != nil {
 		return fmt.Errorf("failed to create event recorder: %v", err)
 	}
+	// Data gatherers are loaded depending on what the Kubernetes API supports.
+	// First, let's do a /api discovery to see what the API supports.
+	discoveryClient, err := k8s.NewDiscoveryClient("")
+	if err != nil {
+		return fmt.Errorf("failed to create a discovery client: %v", err)
+	}
 
+	_, resources, err := discoveryClient.ServerGroupsAndResources()
+	if err != nil {
+		return fmt.Errorf("failed to get server resources: %v", err)
+	}
+	supported := sets.NewString()
+	for _, r := range resources {
+		gv, err := schema.ParseGroupVersion(r.GroupVersion)
+		if err != nil {
+			log.Error(err, "Failed to parse group version")
+		}
+		for _, r2 := range r.APIResources {
+			supported.Insert(gv.WithResource(r2.Name).String())
+		}
+	}
+	log.V(logs.Debug).Info("Supported", "resources", supported.List())
 	dataGatherers := map[string]datagatherer.DataGatherer{}
 
 	// load datagatherer config and boot each one
 	for _, dgConfig := range config.DataGatherers {
+		if c, ok := dgConfig.Config.(*k8s.ConfigDynamic); ok {
+			gvr := c.GroupVersionResource
+			if !supported.Has(gvr.String()) {
+				log.Info(
+					"Skipping DataGatherer",
+					"name", dgConfig.Name,
+					"reason", "GroupVersionResource not installed",
+					"groupVersionResource", gvr,
+				)
+				continue
+			}
+		}
 		kind := dgConfig.Kind
 		if dgConfig.DataPath != "" {
 			kind = "local"
@@ -213,17 +248,16 @@ func Run(cmd *cobra.Command, args []string) (returnErr error) {
 	// too, it will backoff and retry of its own accord. Initial boot
 	// will only be delayed by a max of 5 seconds.
 	bootCtx, bootCancel := context.WithTimeout(gctx, 5*time.Second)
-	defer bootCancel()
-	for _, dgConfig := range config.DataGatherers {
-		dg := dataGatherers[dgConfig.Name]
+	for dgName, dg := range dataGatherers {
 		// wait for the informer to complete an initial sync, we do this to
 		// attempt to have an initial set of data for the first upload of
 		// the run.
 		if err := dg.WaitForCacheSync(bootCtx.Done()); err != nil {
 			// log sync failure, this might recover in future
-			log.Error(err, "Failed to complete initial sync of DataGatherer", "kind", dgConfig.Kind, "name", dgConfig.Name)
+			log.Error(err, "Failed to complete initial sync of DataGatherer", "name", dgName)
 		}
 	}
+	bootCancel()
 
 	// begin the datagathering loop, periodically sending data to the
 	// configured output using data in datagatherer caches or refreshing from