plugin/kubernetes: allow trimming down of cached items. (#2128)

* Convert to runtime.Object to smaller structs

This adds conversion for all the objects we want to keep in the cache.
It keeps the minimum for CoreDNS to function and throws away the rest.

The conversion:
api.Endpoints -> object.Endpoints
api.Pod       -> object.Pod
api.Serivce   -> object.Service

We needed to copy some client-go stuff to insert a conversion function
into NewIndexInformers.

Some unrelated cleanups in the watch functionality as that needed to be
touched because of the above translation of objects.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Reduce test line-count

Signed-off-by: Miek Gieben <miek@miek.nl>

* ....and fix test

Signed-off-by: Miek Gieben <miek@miek.nl>

* Drop use of append

Signed-off-by: Miek Gieben <miek@miek.nl>

* cosmetic changes

Signed-off-by: Miek Gieben <miek@miek.nl>

* that was a typo

Signed-off-by: Miek Gieben <miek@miek.nl>

* re-introduce append here

We can't really use len() here because we don't know the number before
hand.

Signed-off-by: Miek Gieben <miek@miek.nl>

* comment in better place

Signed-off-by: Miek Gieben <miek@miek.nl>

* Make the timestamp a bool; thats where it is used for

Signed-off-by: Miek Gieben <miek@miek.nl>

* Set incoming object to nil

Explicataliy discard the converted object; we did a deep copy it's
not needed anymore.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Per Chris's comment

Signed-off-by: Miek Gieben <miek@miek.nl>

1 files changed, 72 insertions, 0 deletions

diff --git a/plugin/kubernetes/object/pod.go b/plugin/kubernetes/object/pod.go
new file mode 100644
index 000000000..9f0ba48ad
--- /dev/null
+++ b/plugin/kubernetes/object/pod.go
@@ -0,0 +1,72 @@
+package object
+
+import (
+	api "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/runtime"
+)
+
+// Pod is a stripped down api.Pod with only the items we need for CoreDNS.
+type Pod struct {
+	Version   string
+	PodIP     string
+	Name      string
+	Namespace string
+	Deleting  bool
+
+	*Empty
+}
+
+// ToPod converts an api.Pod to a *Pod.
+func ToPod(obj interface{}) interface{} {
+	pod, ok := obj.(*api.Pod)
+	if !ok {
+		return nil
+	}
+
+	p := &Pod{
+		Version:   pod.GetResourceVersion(),
+		PodIP:     pod.Status.PodIP,
+		Namespace: pod.GetNamespace(),
+		Name:      pod.GetName(),
+	}
+	t := pod.ObjectMeta.DeletionTimestamp
+	if t != nil {
+		p.Deleting = !(*t).Time.IsZero()
+	}
+
+	*pod = api.Pod{}
+
+	return p
+}
+
+var _ runtime.Object = &Pod{}
+
+// DeepCopyObject implements the ObjectKind interface.
+func (p *Pod) DeepCopyObject() runtime.Object {
+	p1 := &Pod{
+		Version:   p.Version,
+		PodIP:     p.PodIP,
+		Namespace: p.Namespace,
+		Name:      p.Name,
+		Deleting:  p.Deleting,
+	}
+	return p1
+}
+
+// GetNamespace implements the metav1.Object interface.
+func (p *Pod) GetNamespace() string { return p.Namespace }
+
+// SetNamespace implements the metav1.Object interface.
+func (p *Pod) SetNamespace(namespace string) {}
+
+// GetName implements the metav1.Object interface.
+func (p *Pod) GetName() string { return p.Name }
+
+// SetName implements the metav1.Object interface.
+func (p *Pod) SetName(name string) {}
+
+// GetResourceVersion implements the metav1.Object interface.
+func (p *Pod) GetResourceVersion() string { return p.Version }
+
+// SetResourceVersion implements the metav1.Object interface.
+func (p *Pod) SetResourceVersion(version string) {}