Handle overlapping deployments gracefully

1. When overlapping deployments are discovered, annotate them
2. Expose those overlapping annotations as warnings in kubectl describe
3. Only respect the earliest updated one (skip syncing all other overlapping deployments)
4. Use indexer instead of store for deployment lister

pkg/controller/deployment/util/deployment_util.go

@@ -58,6 +58,12 @@ const (
 	RollbackTemplateUnchanged = "DeploymentRollbackTemplateUnchanged"
 	// RollbackDone is the done rollback event reason
 	RollbackDone = "DeploymentRollback"
+	// OverlapAnnotation marks deployments with overlapping selector with other deployments
+	// TODO: Delete this annotation when we gracefully handle overlapping selectors. See https://github.com/kubernetes/kubernetes/issues/2210
+	OverlapAnnotation = "deployment.kubernetes.io/error-selector-overlapping-with"
+	// SelectorUpdateAnnotation marks the last time deployment selector update
+	// TODO: Delete this annotation when we gracefully handle overlapping selectors. See https://github.com/kubernetes/kubernetes/issues/2210
+	SelectorUpdateAnnotation = "deployment.kubernetes.io/selector-updated-at"
 )
 
 // MaxRevision finds the highest revision in the replica sets
@@ -791,3 +797,42 @@ func DeploymentDeepCopy(deployment *extensions.Deployment) (*extensions.Deployme
 	}
 	return copied, nil
 }
+
+// SelectorUpdatedBefore returns true if the former deployment's selector
+// is updated before the latter, false otherwise
+func SelectorUpdatedBefore(d1, d2 *extensions.Deployment) bool {
+	t1, t2 := LastSelectorUpdate(d1), LastSelectorUpdate(d2)
+	return t1.Before(t2)
+}
+
+// LastSelectorUpdate returns the last time given deployment's selector is updated
+func LastSelectorUpdate(d *extensions.Deployment) unversioned.Time {
+	t := d.Annotations[SelectorUpdateAnnotation]
+	if len(t) > 0 {
+		parsedTime, err := time.Parse(t, time.RFC3339)
+		// If failed to parse the time, use creation timestamp instead
+		if err != nil {
+			return d.CreationTimestamp
+		}
+		return unversioned.Time{Time: parsedTime}
+	}
+	// If it's never updated, use creation timestamp instead
+	return d.CreationTimestamp
+}
+
+// BySelectorLastUpdateTime sorts a list of deployments by the last update time of their selector,
+// first using their creation timestamp and then their names as a tie breaker.
+type BySelectorLastUpdateTime []extensions.Deployment
+
+func (o BySelectorLastUpdateTime) Len() int      { return len(o) }
+func (o BySelectorLastUpdateTime) Swap(i, j int) { o[i], o[j] = o[j], o[i] }
+func (o BySelectorLastUpdateTime) Less(i, j int) bool {
+	ti, tj := LastSelectorUpdate(&o[i]), LastSelectorUpdate(&o[j])
+	if ti.Equal(tj) {
+		if o[i].CreationTimestamp.Equal(o[j].CreationTimestamp) {
+			return o[i].Name < o[j].Name
+		}
+		return o[i].CreationTimestamp.Before(o[j].CreationTimestamp)
+	}
+	return ti.Before(tj)
+}