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Support burst in stateful set scale up and down

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The alpha field podManagementPolicy defines how pods are created,
deleted, and replaced. The new `Parallel` policy will replace pods
as fast as possible, not waiting for the pod to be `Ready` or providing
an order. This allows for advanced clustered software to take advantage
of rapid changes in scale.
This commit is contained in:
Clayton Coleman
2017-04-25 00:39:32 -04:00
parent 95ce463e95
commit 2861ae5eb9
30 changed files with 889 additions and 416 deletions
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43
pkg/controller/statefulset/stateful_set_control.go
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@@ -50,6 +50,12 @@ type defaultStatefulSetControl struct {
podControl StatefulPodControlInterface
}
// UpdateStatefulSet executes the core logic loop for a stateful set, applying the predictable and
// consistent monotonic update strategy by default - scale up proceeds in ordinal order, no new pod
// is created while any pod is unhealthy, and pods are terminated in descending order. The burst
// strategy allows these constraints to be relaxed - pods will be created and deleted eagerly and
// in no particular order. Clients using the burst strategy should be careful to ensure they
// understand the consistency implications of having unpredictable numbers of pods available.
func (ssc *defaultStatefulSetControl) UpdateStatefulSet(set *apps.StatefulSet, pods []*v1.Pod) error {
replicaCount := int(*set.Spec.Replicas)
// slice that will contain all Pods such that 0 <= getOrdinal(pod) < set.Spec.Replicas
@@ -118,6 +124,8 @@ func (ssc *defaultStatefulSetControl) UpdateStatefulSet(set *apps.StatefulSet, p
return nil
}
monotonic := !allowsBurst(set)
// Examine each replica with respect to its ordinal
for i := range replicas {
// delete and recreate failed pods
@@ -128,23 +136,29 @@ func (ssc *defaultStatefulSetControl) UpdateStatefulSet(set *apps.StatefulSet, p
}
replicas[i] = newStatefulSetPod(set, i)
}
// If we find a Pod that has not been created we create the Pod immediately and return
// If we find a Pod that has not been created we create the Pod
if !isCreated(replicas[i]) {
return ssc.podControl.CreateStatefulPod(set, replicas[i])
if err := ssc.podControl.CreateStatefulPod(set, replicas[i]); err != nil {
return err
}
// if the set does not allow bursting, return immediately
if monotonic {
return nil
}
// pod created, no more work possible for this round
continue
}
// If we find a Pod that is currently terminating, we must wait until graceful deletion
// completes before we continue to make progress.
if isTerminating(replicas[i]) {
glog.V(2).Infof("StatefulSet %s is waiting for Pod %s to Terminate",
set.Name, replicas[i].Name)
// completes before we continue to make progress.
if isTerminating(replicas[i]) && monotonic {
glog.V(2).Infof("StatefulSet %s is waiting for Pod %s to Terminate", set.Name, replicas[i].Name)
return nil
}
// If we have a Pod that has been created but is not running and ready we can not make progress.
// We must ensure that all for each Pod, when we create it, all of its predecessors, with respect to its
// ordinal, are Running and Ready.
if !isRunningAndReady(replicas[i]) {
glog.V(2).Infof("StatefulSet %s is waiting for Pod %s to be Running and Ready",
set.Name, replicas[i].Name)
if !isRunningAndReady(replicas[i]) && monotonic {
glog.V(2).Infof("StatefulSet %s is waiting for Pod %s to be Running and Ready", set.Name, replicas[i].Name)
return nil
}
// Enforce the StatefulSet invariants
@@ -166,13 +180,18 @@ func (ssc *defaultStatefulSetControl) UpdateStatefulSet(set *apps.StatefulSet, p
// We will wait for all predecessors to be Running and Ready prior to attempting a deletion.
// We will terminate Pods in a monotonically decreasing order over [len(pods),set.Spec.Replicas).
// Note that we do not resurrect Pods in this interval.
if unhealthy > 0 {
if unhealthy > 0 && monotonic {
glog.V(2).Infof("StatefulSet %s is waiting on %d Pods", set.Name, unhealthy)
return nil
}
if target := len(condemned) - 1; target >= 0 {
for target := len(condemned) - 1; target >= 0; target-- {
glog.V(2).Infof("StatefulSet %s terminating Pod %s", set.Name, condemned[target])
return ssc.podControl.DeleteStatefulPod(set, condemned[target])
if err := ssc.podControl.DeleteStatefulPod(set, condemned[target]); err != nil {
return err
}
if monotonic {
return nil
}
}
return nil
}