Add the resource version to api.*List items from etcd

Allows clients to watch more easily (can invoke Get, then
Watch).

pkg/tools/etcd_tools.go

@@ -117,22 +117,29 @@ func etcdErrorIndex(err error) (uint64, bool) {
 	return 0, false
 }
 
-func (h *EtcdHelper) listEtcdNode(key string) ([]*etcd.Node, error) {
+func (h *EtcdHelper) listEtcdNode(key string) ([]*etcd.Node, uint64, error) {
 	result, err := h.Client.Get(key, false, true)
 	if err != nil {
+		index, ok := etcdErrorIndex(err)
+		if !ok {
+			index = 0
+		}
 		nodes := make([]*etcd.Node, 0)
 		if IsEtcdNotFound(err) {
-			return nodes, nil
+			return nodes, index, nil
 		} else {
-			return nodes, err
+			return nodes, index, err
 		}
 	}
-	return result.Node.Nodes, nil
+	return result.Node.Nodes, result.EtcdIndex, nil
 }
 
-// Extract a go object per etcd node into a slice.
-func (h *EtcdHelper) ExtractList(key string, slicePtr interface{}) error {
-	nodes, err := h.listEtcdNode(key)
+// Extract a go object per etcd node into a slice with the resource version.
+func (h *EtcdHelper) ExtractList(key string, slicePtr interface{}, resourceVersion *uint64) error {
+	nodes, index, err := h.listEtcdNode(key)
+	if resourceVersion != nil {
+		*resourceVersion = index
+	}
 	if err != nil {
 		return err
 	}

pkg/tools/etcd_tools_test.go

@@ -66,6 +66,7 @@ func TestExtractList(t *testing.T) {
 	fakeClient := NewFakeEtcdClient(t)
 	fakeClient.Data["/some/key"] = EtcdResponseWithError{
 		R: &etcd.Response{
+			EtcdIndex: 10,
 			Node: &etcd.Node{
 				Nodes: []*etcd.Node{
 					{
@@ -92,10 +93,14 @@ func TestExtractList(t *testing.T) {
 
 	var got []api.Pod
 	helper := EtcdHelper{fakeClient, codec, versioner}
-	err := helper.ExtractList("/some/key", &got)
+	resourceVersion := uint64(0)
+	err := helper.ExtractList("/some/key", &got, &resourceVersion)
 	if err != nil {
 		t.Errorf("Unexpected error %#v", err)
 	}
+	if resourceVersion != 10 {
+		t.Errorf("Unexpected resource version %d", resourceVersion)
+	}
 
 	for i := 0; i < len(expect); i++ {
 		if !reflect.DeepEqual(got[i], expect[i]) {