Prevent Kubelet from incorrectly interpreting "not yet started" pods as "ready to terminate pods" by unifying responsibility for pod lifecycle into pod worker
As of now, we allow PDBs to be applied to pods via
selectors, so there can be unmanaged pods(pods that
don't have backing controllers) but still have PDBs associated.
Such pods are to be logged instead of immediately throwing
a sync error. This ensures disruption controller is
not frequently updating the status subresource and thus
preventing excessive and expensive writes to etcd.
A number of race conditions exist when pods are terminated early in
their lifecycle because components in the kubelet need to know "no
running containers" or "containers can't be started from now on" but
were relying on outdated state.
Only the pod worker knows whether containers are being started for
a given pod, which is required to know when a pod is "terminated"
(no running containers, none coming). Move that responsibility and
podKiller function into the pod workers, and have everything that
was killing the pod go into the UpdatePod loop. Split syncPod into
three phases - setup, terminate containers, and cleanup pod - and
have transitions between those methods be visible to other
components. After this change, to kill a pod you tell the pod worker
to UpdatePod({UpdateType: SyncPodKill, Pod: pod}).
Several places in the kubelet were incorrect about whether they
were handling terminating (should stop running, might have
containers) or terminated (no running containers) pods. The pod worker
exposes methods that allow other loops to know when to set up or tear
down resources based on the state of the pod - these methods remove
the possibility of race conditions by ensuring a single component is
responsible for knowing each pod's allowed state and other components
simply delegate to checking whether they are in the window by UID.
Removing containers now no longer blocks final pod deletion in the
API server and are handled as background cleanup. Node shutdown
no longer marks pods as failed as they can be restarted in the
next step.
See https://docs.google.com/document/d/1Pic5TPntdJnYfIpBeZndDelM-AbS4FN9H2GTLFhoJ04/edit# for details
Co-Authored-By: Riaan Kleinhans <riaan@ii.coop>
e2e test validates the following 3 extra endpoints
- patchAppsV1NamespacedStatefulSet
- listAppsV1StatefulSetForAllNamespaces
- deleteAppsV1CollectionNamespacedStatefulSet
e2e test validates the following 3 extra endpoints
- replaceAppsV1NamespacedDaemonSetStatus
- readAppsV1NamespacedDaemonSetStatus
- patchAppsV1NamespacedDaemonSetStatus
e2e test validates the following 3 extra endpoints
- replaceAppsV1NamespacedReplicaSetStatus
- readAppsV1NamespacedReplicaSetStatus
- patchAppsV1NamespacedReplicaSetStatus
e2e test validates the following 3 endpoints
- readAppsV1NamespacedDeploymentStatus
- replaceAppsV1NamespacedDeploymentStatus
- patchAppsV1NamespacedDeploymentStatus
e2e test validates the following 3 endpoints
- patchAppsV1NamespacedStatefulSetStatus
- readAppsV1NamespacedStatefulSetStatus
- replaceAppsV1NamespacedStatefulSetStatus
