two level json decoding

pkg/controller/controller.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"net/http"
 	"time"
 
@@ -30,9 +29,14 @@ var (
 	}
 )
 
+type rawEvent struct {
+	Type   string
+	Object json.RawMessage
+}
+
 type Event struct {
 	Type   string
-	Object spec.EtcdCluster
+	Object *spec.EtcdCluster
 }
 
 type Controller struct {
@@ -181,51 +185,65 @@ func (c *Controller) createTPR() error {
 }
 
 func monitorEtcdCluster(host, ns string, httpClient *http.Client, watchVersion string) (<-chan *Event, <-chan error) {
-	events := make(chan *Event)
+	eventCh := make(chan *Event)
 	// On unexpected error case, controller should exit
-	errc := make(chan error, 1)
+	errCh := make(chan error, 1)
 	go func() {
 		for {
 			resp, err := k8sutil.WatchETCDCluster(host, ns, httpClient, watchVersion)
 			if err != nil {
-				errc <- err
+				errCh <- err
 				return
 			}
 			if resp.StatusCode != 200 {
 				resp.Body.Close()
-				errc <- errors.New("Invalid status code: " + resp.Status)
+				errCh <- errors.New("Invalid status code: " + resp.Status)
 				return
 			}
 			log.Printf("watching at %v", watchVersion)
+			decoder := json.NewDecoder(resp.Body)
 			for {
-				decoder := json.NewDecoder(resp.Body)
-				ev := new(Event)
-				err = decoder.Decode(ev)
+				ev, err := pollEvent(decoder)
 				if err != nil {
-					if err == io.EOF {
+					if err == io.EOF { // apiserver will close stream periodically
 						break
 					}
-					b, readErr := ioutil.ReadAll(decoder.Buffered())
-					if readErr != nil {
-						log.Errorf("fail to read from json decoder buffer: %v", readErr)
-					}
-					log.Errorf("failed to decode event (%s) from apiserver: %v", b, err)
-					errc <- err
+					errCh <- err
 					return
 				}
-				if ev.Type == "ERROR" {
-					// TODO: We couldn't decode error status from watch stream on apiserver.
-					//       Working around by restart and go through recover path.
-					//       We strive to fix it in k8s upstream.
-					log.Fatal("unkown watch error from apiserver")
-				}
-				log.Printf("etcd cluster event: %v %#v", ev.Type, ev.Object)
+				log.Printf("etcd cluster event: %v %v", ev.Type, ev.Object.Spec)
 				watchVersion = ev.Object.ObjectMeta.ResourceVersion
-				events <- ev
+				eventCh <- ev
 			}
 			resp.Body.Close()
 		}
 	}()
 
-	return events, errc
+	return eventCh, errCh
+}
+
+func pollEvent(decoder *json.Decoder) (*Event, error) {
+	re := &rawEvent{}
+	err := decoder.Decode(re)
+	if err != nil {
+		if err == io.EOF {
+			return nil, err
+		}
+		log.Errorf("fail to decode raw event from apiserver: %v", err)
+		return nil, err
+	}
+	if re.Type == "ERROR" {
+		log.Fatalf("watch error from apiserver. (TODO: separate transient and fatal error)\n"+
+			"Error message: %s", re.Object)
+	}
+	ev := &Event{
+		Type:   re.Type,
+		Object: &spec.EtcdCluster{},
+	}
+	err = json.Unmarshal(re.Object, ev.Object)
+	if err != nil {
+		log.Errorf("fail to unmarshal EtcdCluster object from data (%s): %v", re.Object, err)
+		return nil, err
+	}
+	return ev, nil
 }