Updating the semantics of MaxSurge and unavailability

pkg/kubectl/rolling_updater.go

@@ -60,25 +60,27 @@ type RollingUpdaterConfig struct {
 	// CleanupPolicy defines the cleanup action to take after the deployment is
 	// complete.
 	CleanupPolicy RollingUpdaterCleanupPolicy
-	// The maximum number of pods that can be unavailable during the update.
+	// MaxUnavailable is the maximum number of pods that can be unavailable during the update.
-	// Value can be an absolute number (ex: 5) or a percentage of total pods at
+	// Value can be an absolute number (ex: 5) or a percentage of desired pods (ex: 10%).
-	// the start of update (ex: 10%). Absolute number is calculated from
+	// Absolute number is calculated from percentage by rounding up.
-	// percentage by rounding up. This can not be 0 if MaxSurge is 0. By
+	// This can not be 0 if MaxSurge is 0.
-	// default, a fixed value of 1 is used. Example: when this is set to 30%,
+	// By default, a fixed value of 1 is used.
-	// the old RC can be scaled down by 30% immediately when the rolling update
+	// Example: when this is set to 30%, the old RC can be scaled down to 70% of desired pods
-	// starts. Once new pods are ready, old RC can be scaled down further,
+	// immediately when the rolling update starts. Once new pods are ready, old RC
-	// followed by scaling up the new RC, ensuring that at least 70% of original
+	// can be scaled down further, followed by scaling up the new RC, ensuring
-	// number of pods are available at all times during the update.
+	// that the total number of pods available at all times during the update is at
+	// least 70% of desired pods.
 	MaxUnavailable util.IntOrString
-	// The maximum number of pods that can be scheduled above the original
+	// MaxSurge is the maximum number of pods that can be scheduled above the desired number of pods.
-	// number of pods. Value can be an absolute number (ex: 5) or a percentage of total
+	// Value can be an absolute number (ex: 5) or a percentage of desired pods (ex: 10%).
-	// pods at the start of the update (ex: 10%). This can not be 0 if
+	// This can not be 0 if MaxUnavailable is 0.
-	// MaxUnavailable is 0. Absolute number is calculated from percentage by
+	// Absolute number is calculated from percentage by rounding up.
-	// rounding up. By default, a value of 1 is used. Example: when this is set
+	// By default, a value of 1 is used.
-	// to 30%, the new RC can be scaled up by 30% immediately when the rolling
+	// Example: when this is set to 30%, the new RC can be scaled up immediately
-	// update starts. Once old pods have been killed, new RC can be scaled up
+	// when the rolling update starts, such that the total number of old and new pods do not exceed
+	// 130% of desired pods. Once old pods have been killed, new RC can be scaled up
 	// further, ensuring that total number of pods running at any time during
-	// the update is atmost 130% of original pods.
+	// the update is atmost 130% of desired pods.
 	MaxSurge util.IntOrString
 }
 
@@ -197,12 +199,12 @@ func (r *RollingUpdater) Update(config *RollingUpdaterConfig) error {
 			oldRc.Name, originalReplicasAnnotation, oldRc.Annotations[originalReplicasAnnotation])
 	}
 	// The maximum pods which can go unavailable during the update.
-	maxUnavailable, err := extractMaxValue(config.MaxUnavailable, "maxUnavailable", original)
+	maxUnavailable, err := extractMaxValue(config.MaxUnavailable, "maxUnavailable", desired)
 	if err != nil {
 		return err
 	}
 	// The maximum scaling increment.
-	maxSurge, err := extractMaxValue(config.MaxSurge, "maxSurge", original)
+	maxSurge, err := extractMaxValue(config.MaxSurge, "maxSurge", desired)
 	if err != nil {
 		return err
 	}
@@ -480,8 +482,8 @@ func (r *RollingUpdater) cleanupWithClients(oldRc, newRc *api.ReplicationControl
 }
 
 // func extractMaxValue is a helper to extract config max values as either
-// absolute numbers or based on percentages of the original rc.
+// absolute numbers or based on percentages of the given value.
-func extractMaxValue(field util.IntOrString, name string, original int) (int, error) {
+func extractMaxValue(field util.IntOrString, name string, value int) (int, error) {
 	switch field.Kind {
 	case util.IntstrInt:
 		if field.IntVal < 0 {
@@ -497,7 +499,7 @@ func extractMaxValue(field util.IntOrString, name string, original int) (int, er
 		if v < 0 {
 			return 0, fmt.Errorf("%s must be >= 0", name)
 		}
-		return int(math.Ceil(float64(original) * (float64(v)) / 100)), nil
+		return int(math.Ceil(float64(value) * (float64(v)) / 100)), nil
 	}
 	return 0, fmt.Errorf("invalid kind %q for %s", field.Kind, name)
 }

pkg/kubectl/rolling_updater_test.go

@@ -538,7 +538,7 @@ Scaling foo-v1 down to 0
 				down{oldReady: 10, newReady: 20, to: 0},
 			},
 			output: `Created foo-v2
-Scaling up foo-v2 from 0 to 20, scaling down foo-v1 from 10 to 0 (keep 10 pods available, don't exceed 40 pods)
+Scaling up foo-v2 from 0 to 20, scaling down foo-v1 from 10 to 0 (keep 10 pods available, don't exceed 70 pods)
 Scaling foo-v2 up to 20
 Scaling foo-v1 down to 0
 `,