This commit wires together the graceful delete option for pods
on the Kubelet. When a pod is deleted on the API server, a
grace period is calculated that is based on the
Pod.Spec.TerminationGracePeriodInSeconds, the user's provided grace
period, or a default. The grace period can only shrink once set.
The value provided by the user (or the default) is set onto metadata
as DeletionGracePeriod.
When the Kubelet sees a pod with DeletionTimestamp set, it uses the
value of ObjectMeta.GracePeriodSeconds as the grace period
sent to Docker. When updating status, if the pod has DeletionTimestamp
set and all containers are terminated, the Kubelet will update the
status one last time and then invoke Delete(pod, grace: 0) to
clean up the pod immediately.
In order to support graceful deletion, the resource object will
need access to the TTL value in etcd. Also, in the future we
may want to get the creation index (distinct from modifiedindex)
and expose it to clients. Change EtcdResourceVersioner to be
more type specific (objects vs lists) and provide a default
implementation that relies on the internal API convention.
Also, rename etcd_tools.go to etcd_helper.go and split a few
things up.
Create a new MetadataAccessor interface that combines both
and use it where previously latest.ResourceVersioner and SelfLinker
were being used.
Adds Namespace to the get/set interface. Adds TODO about future
fast path for metadata (as per thockin's comment)
