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PVC protection controller: clarify pod shutdown #99626

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merged 1 commit into from Mar 4, 2021
Merged

PVC protection controller: clarify pod shutdown #99626

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23 changes: 8 additions & 15 deletions pkg/controller/volume/pvcprotection/pvc_protection_controller.go
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Expand Up @@ -311,23 +311,16 @@ func (c *Controller) podUsesPVC(pod *v1.Pod, pvc *v1.PersistentVolumeClaim) bool
// podIsShutDown returns true if kubelet is done with the pod or
// it was force-deleted.
func podIsShutDown(pod *v1.Pod) bool {
// The following text is based on how pod shutdown was
// initially described to me. During PR review, it was pointed out
// that this is not correct: "deleteGracePeriodSeconds tells
// kubelet when it can start force terminating the
// containers. Volume teardown only starts after containers
// are termianted. So there is an additional time period after
// the grace period where volume teardown is happening."
//
// TODO (https://github.com/kubernetes/enhancements/issues/1698#issuecomment-655344680):
// investigate what kubelet really does and if necessary,
// add some other signal for "kubelet is done". For now the check
// is used only for ephemeral volumes, because it
// is needed to avoid the deadlock.
//
// A pod that has a deletionTimestamp and a zero
// deletionGracePeriodSeconds
// a) has been processed by kubelet and is ready for deletion or
// a) has been processed by kubelet and was set up for deletion
// by the apiserver:
// - canBeDeleted has verified that volumes were unpublished
// https://github.com/kubernetes/kubernetes/blob/5404b5a28a2114299608bab00e4292960dd864a0/pkg/kubelet/kubelet_pods.go#L980
// - deletionGracePeriodSeconds was set via a delete
// with zero GracePeriodSeconds
// https://github.com/kubernetes/kubernetes/blob/5404b5a28a2114299608bab00e4292960dd864a0/pkg/kubelet/status/status_manager.go#L580-L592
// or
// b) was force-deleted.
//
// It's now just waiting for garbage collection. We could wait
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