Retry to watch for builds

This fixes a bug when running, e.g.:

  $ oc start-build --wait --follow my-build

In some cases the watcher expires and we need to try again with a new
watcher.

Author: rhcarvalho

pkg/build/registry/rest.go

@@ -6,6 +6,7 @@ import (
 
 	kapi "k8s.io/kubernetes/pkg/api"
 	"k8s.io/kubernetes/pkg/api/rest"
+	"k8s.io/kubernetes/pkg/api/unversioned"
 	"k8s.io/kubernetes/pkg/fields"
 
 	"github.com/openshift/origin/pkg/build/api"
@@ -20,33 +21,44 @@ var ErrUnknownBuildPhase = fmt.Errorf("unknown build phase")
 func WaitForRunningBuild(watcher rest.Watcher, ctx kapi.Context, build *api.Build, timeout time.Duration) (*api.Build, bool, error) {
 	fieldSelector := fields.OneTermEqualSelector("metadata.name", build.Name)
 	options := &kapi.ListOptions{FieldSelector: fieldSelector, ResourceVersion: build.ResourceVersion}
-	w, err := watcher.Watch(ctx, options)
-	if err != nil {
-		return nil, false, err
-	}
-	defer w.Stop()
 
-	ch := w.ResultChan()
-	observed := build
 	expire := time.After(timeout)
-	for {
-		select {
-		case event := <-ch:
-			obj, ok := event.Object.(*api.Build)
-			if !ok {
-				return observed, false, fmt.Errorf("received unknown object while watching for builds")
-			}
-			observed = obj
 
-			switch obj.Status.Phase {
-			case api.BuildPhaseRunning, api.BuildPhaseComplete, api.BuildPhaseFailed, api.BuildPhaseError, api.BuildPhaseCancelled:
-				return observed, true, nil
-			case api.BuildPhaseNew, api.BuildPhasePending:
-			default:
-				return observed, false, ErrUnknownBuildPhase
+watcherLoop:
+	for {
+		w, err := watcher.Watch(ctx, options)
+		if err != nil {
+			return nil, false, err
+		}
+		defer w.Stop()
+		ch := w.ResultChan()
+	eventLoop:
+		for {
+			select {
+			case event := <-ch:
+				switch observed := event.Object.(type) {
+				case *api.Build:
+					switch observed.Status.Phase {
+					case api.BuildPhaseRunning, api.BuildPhaseComplete, api.BuildPhaseFailed, api.BuildPhaseError, api.BuildPhaseCancelled:
+						// Build has started, return it.
+						return observed, true, nil
+					case api.BuildPhaseNew, api.BuildPhasePending:
+						// Build haven't started yet, continue waiting for more events.
+						continue eventLoop
+					default:
+						// Build has an unknown phase.
+						return observed, false, ErrUnknownBuildPhase
+					}
+				case *unversioned.Status:
+					if observed.Reason == unversioned.StatusReasonExpired {
+						// The watcher expired, need to start over with a new watcher.
+						continue watcherLoop
+					}
+				}
+				return build, false, fmt.Errorf("received unknown object while watching for builds: %v", event.Object)
+			case <-expire:
+				return build, false, nil
 			}
-		case <-expire:
-			return observed, false, nil
 		}
 	}
 }