Add an intermediate API layer that uses containers/storage, and a
containers/image that has been patched to use it, to manage images and
containers, storing the data that we need to know about containers and
pods in the metadata fields provided by containers/storage.
While ocid manages pods and containers as different types of items, with
disjoint sets of IDs and names, it remains true that every pod includes
at least one container. When a container's only purpose is to serve as
a home for namespaces that are shared with the other containers in the
pod, it is referred to as the pod's infrastructure container.
At the storage level, a pod is stored as its set of containers. We keep
track of both pod IDs and container IDs in the metadata field of
Container objects that the storage library manages for us. Containers
which bear the same pod ID are members of the pod which has that ID.
Other information about the pod, which ocid needs to remember in order
to answer requests for information about the pod, is also kept in the
metadata field of its member containers.
The container's runtime configuration should be stored in the
container's ContainerDirectory, and used as a template. Each time the
container is about to be started, its layer should be mounted, that
configuration template should be read, the template's rootfs location
should be replaced with the mountpoint for the container's layer, and
the result should be saved to the container's ContainerRunDirectory,
for use as the configuration for the container.
Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>
