From 6db9601772c1ef6b14822c98366947ecfa54739e Mon Sep 17 00:00:00 2001
From: Dan Mace <dmace@redhat.com>
Date: Mon, 28 Sep 2015 14:52:01 -0400
Subject: [PATCH] Support asymmetric rolling rollbacks

Improve the rolling updater rollback/abort function by making it aware
of the original replicas annotation: if the rollback target has the
original replica count recorded, prefer it over the desired annotation
since the update from old to new could have been asymmetrical.

For example, when scaling from 5 to 10, aborting should scale back to 5.
---
 pkg/kubectl/cmd/rollingupdate.go |  5 ++++-
 pkg/kubectl/rolling_updater.go   | 16 +++++++++++-----
 2 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/pkg/kubectl/cmd/rollingupdate.go b/pkg/kubectl/cmd/rollingupdate.go
index 1f86bc21b45..7a283c4f179 100644
--- a/pkg/kubectl/cmd/rollingupdate.go
+++ b/pkg/kubectl/cmd/rollingupdate.go
@@ -296,7 +296,10 @@ func RunRollingUpdate(f *cmdutil.Factory, out io.Writer, cmd *cobra.Command, arg
 		MaxSurge:       util.NewIntOrStringFromInt(1),
 	}
 	if cmdutil.GetFlagBool(cmd, "rollback") {
-		kubectl.AbortRollingUpdate(config)
+		err = kubectl.AbortRollingUpdate(config)
+		if err != nil {
+			return err
+		}
 		client.ReplicationControllers(config.NewRc.Namespace).Update(config.NewRc)
 	}
 	err = updater.Update(config)
diff --git a/pkg/kubectl/rolling_updater.go b/pkg/kubectl/rolling_updater.go
index 25ae11e5737..566772e1607 100644
--- a/pkg/kubectl/rolling_updater.go
+++ b/pkg/kubectl/rolling_updater.go
@@ -562,7 +562,7 @@ func CreateNewControllerFromCurrentController(c *client.Client, namespace, oldNa
 	return newRc, nil
 }
 
-func AbortRollingUpdate(c *RollingUpdaterConfig) {
+func AbortRollingUpdate(c *RollingUpdaterConfig) error {
 	// Swap the controllers
 	tmp := c.OldRc
 	c.OldRc = c.NewRc
@@ -572,12 +572,18 @@ func AbortRollingUpdate(c *RollingUpdaterConfig) {
 		c.NewRc.Annotations = map[string]string{}
 	}
 	c.NewRc.Annotations[sourceIdAnnotation] = fmt.Sprintf("%s:%s", c.OldRc.Name, c.OldRc.UID)
-	desiredSize, found := c.OldRc.Annotations[desiredReplicasAnnotation]
-	if found {
-		fmt.Printf("Found desired replicas.")
-		c.NewRc.Annotations[desiredReplicasAnnotation] = desiredSize
+
+	// Use the original value since the replica count change from old to new
+	// could be asymmetric. If we don't know the original count, we can't safely
+	// roll back to a known good size.
+	originalSize, foundOriginal := tmp.Annotations[originalReplicasAnnotation]
+	if !foundOriginal {
+		return fmt.Errorf("couldn't find original replica count of %q", tmp.Name)
 	}
+	fmt.Fprintf(c.Out, "Setting %q replicas to %s\n", c.NewRc.Name, originalSize)
+	c.NewRc.Annotations[desiredReplicasAnnotation] = originalSize
 	c.CleanupPolicy = DeleteRollingUpdateCleanupPolicy
+	return nil
 }
 
 func GetNextControllerAnnotation(rc *api.ReplicationController) (string, bool) {