// maxUnavailable returns the maximum unavailable pods a rolling deployment can take.
func maxUnavailable(deployment extensions.Deployment) int32 {
if !deploymentutil.IsRollingUpdate(&deployment) {
return int32(0)
}
// Error caught by validation
_, maxUnavailable, _ := deploymentutil.ResolveFenceposts(&deployment.Spec.Strategy.RollingUpdate.MaxSurge, &deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas)
return maxUnavailable
}
// scaleDownOldReplicaSetsForRollingUpdate scales down old replica sets when deployment strategy is "RollingUpdate".
// Need check maxUnavailable to ensure availability
func (dc *DeploymentController) scaleDownOldReplicaSetsForRollingUpdate(allRSs []*extensions.ReplicaSet, oldRSs []*extensions.ReplicaSet, deployment *extensions.Deployment) (int, error) {
_, maxUnavailable, err := deploymentutil.ResolveFenceposts(&deployment.Spec.Strategy.RollingUpdate.MaxSurge, &deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas)
if err != nil {
return 0, err
}
// Check if we can scale down.
minAvailable := deployment.Spec.Replicas - maxUnavailable
minReadySeconds := deployment.Spec.MinReadySeconds
// Find the number of ready pods.
readyPodCount, err := deploymentutil.GetAvailablePodsForReplicaSets(dc.client, allRSs, minReadySeconds)
if err != nil {
return 0, fmt.Errorf("could not find available pods: %v", err)
}
if readyPodCount <= minAvailable {
// Cannot scale down.
return 0, nil
}
sort.Sort(controller.ReplicaSetsByCreationTimestamp(oldRSs))
totalScaledDown := 0
totalScaleDownCount := readyPodCount - minAvailable
for _, targetRS := range oldRSs {
if totalScaledDown >= totalScaleDownCount {
// No further scaling required.
break
}
if targetRS.Spec.Replicas == 0 {
// cannot scale down this ReplicaSet.
continue
}
// Scale down.
scaleDownCount := integer.IntMin(targetRS.Spec.Replicas, totalScaleDownCount-totalScaledDown)
newReplicasCount := targetRS.Spec.Replicas - scaleDownCount
_, _, err = dc.scaleReplicaSetAndRecordEvent(targetRS, newReplicasCount, deployment)
if err != nil {
return totalScaledDown, err
}
totalScaledDown += scaleDownCount
}
return totalScaledDown, nil
}
// Update all pods for a ReplicationController (oldRc) by creating a new
// controller (newRc) with 0 replicas, and synchronously scaling oldRc and
// newRc until oldRc has 0 replicas and newRc has the original # of desired
// replicas. Cleanup occurs based on a RollingUpdaterCleanupPolicy.
//
// Each interval, the updater will attempt to make progress however it can
// without violating any availability constraints defined by the config. This
// means the amount scaled up or down each interval will vary based on the
// timeliness of readiness and the updater will always try to make progress,
// even slowly.
//
// If an update from newRc to oldRc is already in progress, we attempt to
// drive it to completion. If an error occurs at any step of the update, the
// error will be returned.
//
// A scaling event (either up or down) is considered progress; if no progress
// is made within the config.Timeout, an error is returned.
//
// TODO: make this handle performing a rollback of a partially completed
// rollout.
func (r *RollingUpdater) Update(config *RollingUpdaterConfig) error {
out := config.Out
oldRc := config.OldRc
scaleRetryParams := NewRetryParams(config.Interval, config.Timeout)
// Find an existing controller (for continuing an interrupted update) or
// create a new one if necessary.
sourceId := fmt.Sprintf("%s:%s", oldRc.Name, oldRc.UID)
newRc, existed, err := r.getOrCreateTargetController(config.NewRc, sourceId)
if err != nil {
return err
}
if existed {
fmt.Fprintf(out, "Continuing update with existing controller %s.\n", newRc.Name)
} else {
fmt.Fprintf(out, "Created %s\n", newRc.Name)
}
// Extract the desired replica count from the controller.
desiredAnnotation, err := strconv.Atoi(newRc.Annotations[desiredReplicasAnnotation])
if err != nil {
return fmt.Errorf("Unable to parse annotation for %s: %s=%s",
newRc.Name, desiredReplicasAnnotation, newRc.Annotations[desiredReplicasAnnotation])
}
desired := int32(desiredAnnotation)
// Extract the original replica count from the old controller, adding the
// annotation if it doesn't yet exist.
_, hasOriginalAnnotation := oldRc.Annotations[originalReplicasAnnotation]
if !hasOriginalAnnotation {
existing, err := r.c.ReplicationControllers(oldRc.Namespace).Get(oldRc.Name)
if err != nil {
return err
}
originReplicas := strconv.Itoa(int(existing.Spec.Replicas))
applyUpdate := func(rc *api.ReplicationController) {
if rc.Annotations == nil {
rc.Annotations = map[string]string{}
}
rc.Annotations[originalReplicasAnnotation] = originReplicas
}
if oldRc, err = updateRcWithRetries(r.c, existing.Namespace, existing, applyUpdate); err != nil {
return err
}
}
// maxSurge is the maximum scaling increment and maxUnavailable are the maximum pods
// that can be unavailable during a rollout.
maxSurge, maxUnavailable, err := deployment.ResolveFenceposts(&config.MaxSurge, &config.MaxUnavailable, desired)
if err != nil {
return err
}
// Validate maximums.
if desired > 0 && maxUnavailable == 0 && maxSurge == 0 {
return fmt.Errorf("one of maxSurge or maxUnavailable must be specified")
}
// The minumum pods which must remain available througout the update
// calculated for internal convenience.
minAvailable := int32(integer.IntMax(0, int(desired-maxUnavailable)))
// If the desired new scale is 0, then the max unavailable is necessarily
// the effective scale of the old RC regardless of the configuration
// (equivalent to 100% maxUnavailable).
if desired == 0 {
maxUnavailable = oldRc.Spec.Replicas
minAvailable = 0
}
fmt.Fprintf(out, "Scaling up %s from %d to %d, scaling down %s from %d to 0 (keep %d pods available, don't exceed %d pods)\n",
newRc.Name, newRc.Spec.Replicas, desired, oldRc.Name, oldRc.Spec.Replicas, minAvailable, desired+maxSurge)
// give a caller incremental notification and allow them to exit early
goal := desired - newRc.Spec.Replicas
if goal < 0 {
goal = -goal
}
progress := func(complete bool) error {
if config.OnProgress == nil {
return nil
}
progress := desired - newRc.Spec.Replicas
if progress < 0 {
progress = -progress
}
percentage := 100
if !complete && goal > 0 {
percentage = int((goal - progress) * 100 / goal)
}
return config.OnProgress(oldRc, newRc, percentage)
}
// Scale newRc and oldRc until newRc has the desired number of replicas and
// oldRc has 0 replicas.
progressDeadline := time.Now().UnixNano() + config.Timeout.Nanoseconds()
for newRc.Spec.Replicas != desired || oldRc.Spec.Replicas != 0 {
// Store the existing replica counts for progress timeout tracking.
newReplicas := newRc.Spec.Replicas
oldReplicas := oldRc.Spec.Replicas
// Scale up as much as possible.
scaledRc, err := r.scaleUp(newRc, oldRc, desired, maxSurge, maxUnavailable, scaleRetryParams, config)
if err != nil {
return err
}
newRc = scaledRc
// notify the caller if necessary
if err := progress(false); err != nil {
return err
}
// Wait between scaling operations for things to settle.
time.Sleep(config.UpdatePeriod)
// Scale down as much as possible.
scaledRc, err = r.scaleDown(newRc, oldRc, desired, minAvailable, maxUnavailable, maxSurge, config)
if err != nil {
return err
}
oldRc = scaledRc
// notify the caller if necessary
if err := progress(false); err != nil {
return err
}
// If we are making progress, continue to advance the progress deadline.
// Otherwise, time out with an error.
progressMade := (newRc.Spec.Replicas != newReplicas) || (oldRc.Spec.Replicas != oldReplicas)
if progressMade {
progressDeadline = time.Now().UnixNano() + config.Timeout.Nanoseconds()
} else if time.Now().UnixNano() > progressDeadline {
return fmt.Errorf("timed out waiting for any update progress to be made")
}
}
// notify the caller if necessary
if err := progress(true); err != nil {
return err
}
// Housekeeping and cleanup policy execution.
return r.cleanup(oldRc, newRc, config)
}
func (dc *DeploymentController) reconcileOldReplicaSets(allRSs []*extensions.ReplicaSet, oldRSs []*extensions.ReplicaSet, newRS *extensions.ReplicaSet, deployment *extensions.Deployment) (bool, error) {
oldPodsCount := deploymentutil.GetReplicaCountForReplicaSets(oldRSs)
if oldPodsCount == 0 {
// Can't scale down further
return false, nil
}
minReadySeconds := deployment.Spec.MinReadySeconds
allPodsCount := deploymentutil.GetReplicaCountForReplicaSets(allRSs)
newRSAvailablePodCount, err := deploymentutil.GetAvailablePodsForReplicaSets(dc.client, []*extensions.ReplicaSet{newRS}, minReadySeconds)
if err != nil {
return false, fmt.Errorf("could not find available pods: %v", err)
}
_, maxUnavailable, err := deploymentutil.ResolveFenceposts(&deployment.Spec.Strategy.RollingUpdate.MaxSurge, &deployment.Spec.Strategy.RollingUpdate.MaxUnavailable, deployment.Spec.Replicas)
if err != nil {
return false, err
}
// Check if we can scale down. We can scale down in the following 2 cases:
// * Some old replica sets have unhealthy replicas, we could safely scale down those unhealthy replicas since that won't further
// increase unavailability.
// * New replica set has scaled up and it's replicas becomes ready, then we can scale down old replica sets in a further step.
//
// maxScaledDown := allPodsCount - minAvailable - newReplicaSetPodsUnavailable
// take into account not only maxUnavailable and any surge pods that have been created, but also unavailable pods from
// the newRS, so that the unavailable pods from the newRS would not make us scale down old replica sets in a further
// step(that will increase unavailability).
//
// Concrete example:
//
// * 10 replicas
// * 2 maxUnavailable (absolute number, not percent)
// * 3 maxSurge (absolute number, not percent)
//
// case 1:
// * Deployment is updated, newRS is created with 3 replicas, oldRS is scaled down to 8, and newRS is scaled up to 5.
// * The new replica set pods crashloop and never become available.
// * allPodsCount is 13. minAvailable is 8. newRSPodsUnavailable is 5.
// * A node fails and causes one of the oldRS pods to become unavailable. However, 13 - 8 - 5 = 0, so the oldRS won't be scaled down.
// * The user notices the crashloop and does kubectl rollout undo to rollback.
// * newRSPodsUnavailable is 1, since we rolled back to the good replica set, so maxScaledDown = 13 - 8 - 1 = 4. 4 of the crashlooping pods will be scaled down.
// * The total number of pods will then be 9 and the newRS can be scaled up to 10.
//
// case 2:
// Same example, but pushing a new pod template instead of rolling back (aka "roll over"):
// * The new replica set created must start with 0 replicas because allPodsCount is already at 13.
// * However, newRSPodsUnavailable would also be 0, so the 2 old replica sets could be scaled down by 5 (13 - 8 - 0), which would then
// allow the new replica set to be scaled up by 5.
minAvailable := deployment.Spec.Replicas - maxUnavailable
newRSUnavailablePodCount := newRS.Spec.Replicas - newRSAvailablePodCount
maxScaledDown := allPodsCount - minAvailable - newRSUnavailablePodCount
if maxScaledDown <= 0 {
return false, nil
}
// Clean up unhealthy replicas first, otherwise unhealthy replicas will block deployment
// and cause timeout. See https://github.com/kubernetes/kubernetes/issues/16737
cleanupCount, err := dc.cleanupUnhealthyReplicas(oldRSs, deployment, maxScaledDown)
if err != nil {
return false, nil
}
// Scale down old replica sets, need check maxUnavailable to ensure we can scale down
scaledDownCount, err := dc.scaleDownOldReplicaSetsForRollingUpdate(allRSs, oldRSs, deployment)
if err != nil {
return false, nil
}
totalScaledDown := cleanupCount + scaledDownCount
return totalScaledDown > 0, nil
}