From ab1b2218b8d8e8e1b5c94ef029800952dd0f9ae4 Mon Sep 17 00:00:00 2001
From: Dan Winship <danw@gnome.org>
Date: Sun, 10 Feb 2019 14:32:57 -0500
Subject: [PATCH] Replace the controller manager's RESTMapper with a dynamic
 one

---
 cmd/cluster-network-operator/main.go |   6 +-
 pkg/util/k8s/dynamicrestmapper.go    | 110 +++++++++++++++++++++++++++
 2 files changed, 115 insertions(+), 1 deletion(-)
 create mode 100644 pkg/util/k8s/dynamicrestmapper.go

diff --git a/cmd/cluster-network-operator/main.go b/cmd/cluster-network-operator/main.go
index 938cdbd0e4..055079dd19 100644
--- a/cmd/cluster-network-operator/main.go
+++ b/cmd/cluster-network-operator/main.go
@@ -10,6 +10,7 @@ import (
 
 	"github.com/openshift/cluster-network-operator/pkg/apis"
 	"github.com/openshift/cluster-network-operator/pkg/controller"
+	k8sutil "github.com/openshift/cluster-network-operator/pkg/util/k8s"
 	"github.com/operator-framework/operator-sdk/pkg/leader"
 	sdkVersion "github.com/operator-framework/operator-sdk/version"
 	_ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
@@ -82,7 +83,10 @@ func main() {
 	}
 
 	// Create a new Cmd to provide shared dependencies and start components
-	mgr, err := manager.New(cfg, manager.Options{Namespace: namespace})
+	mgr, err := manager.New(cfg, manager.Options{
+		Namespace:      namespace,
+		MapperProvider: k8sutil.NewDynamicRESTMapper,
+	})
 	if err != nil {
 		log.Fatal(err)
 	}
diff --git a/pkg/util/k8s/dynamicrestmapper.go b/pkg/util/k8s/dynamicrestmapper.go
new file mode 100644
index 0000000000..d4bab0dc25
--- /dev/null
+++ b/pkg/util/k8s/dynamicrestmapper.go
@@ -0,0 +1,110 @@
+package k8s
+
+import (
+	"k8s.io/apimachinery/pkg/api/meta"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	utilruntime "k8s.io/apimachinery/pkg/util/runtime"
+	"k8s.io/client-go/discovery"
+	"k8s.io/client-go/rest"
+	"k8s.io/client-go/restmapper"
+)
+
+type DynamicRESTMapper struct {
+	client   discovery.DiscoveryInterface
+	delegate meta.RESTMapper
+}
+
+// NewDynamicRESTMapper returns a RESTMapper that dynamically discovers resource
+// types at runtime. This is in contrast to controller-manager's default RESTMapper, which
+// only checks resource types at startup, and so can't handle the case of first creating a
+// CRD and then creating an instance of that CRD.
+func NewDynamicRESTMapper(cfg *rest.Config) (meta.RESTMapper, error) {
+	client, err := discovery.NewDiscoveryClientForConfig(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	drm := &DynamicRESTMapper{client: client}
+	if err := drm.reload(); err != nil {
+		return nil, err
+	}
+	return drm, nil
+}
+
+func (drm *DynamicRESTMapper) reload() error {
+	gr, err := restmapper.GetAPIGroupResources(drm.client)
+	if err != nil {
+		return err
+	}
+	drm.delegate = restmapper.NewDiscoveryRESTMapper(gr)
+	return nil
+}
+
+// reloadOnError checks if an error indicates that the delegated RESTMapper needs to be
+// reloaded, and if so, reloads it and returns true.
+func (drm *DynamicRESTMapper) reloadOnError(err error) bool {
+	if _, matches := err.(*meta.NoKindMatchError); !matches {
+		return false
+	}
+	err = drm.reload()
+	if err != nil {
+		utilruntime.HandleError(err)
+	}
+	return err == nil
+}
+
+func (drm *DynamicRESTMapper) KindFor(resource schema.GroupVersionResource) (schema.GroupVersionKind, error) {
+	gvk, err := drm.delegate.KindFor(resource)
+	if drm.reloadOnError(err) {
+		gvk, err = drm.delegate.KindFor(resource)
+	}
+	return gvk, err
+}
+
+func (drm *DynamicRESTMapper) KindsFor(resource schema.GroupVersionResource) ([]schema.GroupVersionKind, error) {
+	gvks, err := drm.delegate.KindsFor(resource)
+	if drm.reloadOnError(err) {
+		gvks, err = drm.delegate.KindsFor(resource)
+	}
+	return gvks, err
+}
+
+func (drm *DynamicRESTMapper) ResourceFor(input schema.GroupVersionResource) (schema.GroupVersionResource, error) {
+	gvr, err := drm.delegate.ResourceFor(input)
+	if drm.reloadOnError(err) {
+		gvr, err = drm.delegate.ResourceFor(input)
+	}
+	return gvr, err
+}
+
+func (drm *DynamicRESTMapper) ResourcesFor(input schema.GroupVersionResource) ([]schema.GroupVersionResource, error) {
+	gvrs, err := drm.delegate.ResourcesFor(input)
+	if drm.reloadOnError(err) {
+		gvrs, err = drm.delegate.ResourcesFor(input)
+	}
+	return gvrs, err
+}
+
+func (drm *DynamicRESTMapper) RESTMapping(gk schema.GroupKind, versions ...string) (*meta.RESTMapping, error) {
+	m, err := drm.delegate.RESTMapping(gk, versions...)
+	if drm.reloadOnError(err) {
+		m, err = drm.delegate.RESTMapping(gk, versions...)
+	}
+	return m, err
+}
+
+func (drm *DynamicRESTMapper) RESTMappings(gk schema.GroupKind, versions ...string) ([]*meta.RESTMapping, error) {
+	ms, err := drm.delegate.RESTMappings(gk, versions...)
+	if drm.reloadOnError(err) {
+		ms, err = drm.delegate.RESTMappings(gk, versions...)
+	}
+	return ms, err
+}
+
+func (drm *DynamicRESTMapper) ResourceSingularizer(resource string) (singular string, err error) {
+	s, err := drm.delegate.ResourceSingularizer(resource)
+	if drm.reloadOnError(err) {
+		s, err = drm.delegate.ResourceSingularizer(resource)
+	}
+	return s, err
+}