Block the synchronization of registering NRI plugins during
CRI events to avoid the plugin ending up in an inconsistent
starting state after initial sync (missing pods, containers
or missed events for some pods or containers).
Signed-off-by: Krisztian Litkey <krisztian.litkey@intel.com>
A nil CRIImplementation field can cause a nil pointer dereference and
panic during startup recovery.
Prior to this change, the nri.API struct would have a nil cri
(CRIImplementation) field after nri.NewAPI until nri.Register was
called. Register is called mid-way through initialization of the CRI
plugin, but recovery for containers occurs prior to that. Container
recovery includes establishing new exit monitors for existing containers
that were discovered. When a container exits, NRI plugins are given the
opportunity to be notified about the lifecycle event, and this is done
by accessing that CRIImplementation field inside the nri.API. If a
container exits prior to nri.Register being called, access to the
CRIImplementation field can cause a panic.
Here's the call-path:
* The CRI plugin starts running
[here](ae71819c4f/pkg/cri/server/service.go (L222))
* It then [calls into](ae71819c4f/pkg/cri/server/service.go (L227))
`recover()` to recover state from previous runs of containerd
* `recover()` then attempts to recover all containers through
[`loadContainer()`](ae7d74b9e2/internal/cri/server/restart.go (L175))
* When `loadContainer()` finds a container that is still running, it waits
for the task (internal containerd object) to exit and sets up
[exit monitoring](ae7d74b9e2/internal/cri/server/restart.go (L391))
* Any exit that then happens must be
[handled](ae7d74b9e2/internal/cri/server/events.go (L145))
* Handling an exit includes
[deleting the Task](ae7d74b9e2/internal/cri/server/events.go (L188))
and specifying [`nri.WithContainerExit`](ae7d74b9e2/internal/cri/nri/nri_api_linux.go (L348))
to [notify](ae7d74b9e2/internal/cri/nri/nri_api_linux.go (L356))
any subscribed NRI plugins
* NRI plugins need to know information about the pod (not just the sandbox),
so before a plugin is notified the NRI API package
[queries the Sandbox Store](ae7d74b9e2/internal/cri/nri/nri_api_linux.go (L232))
through the CRI implementation
* The `cri` implementation member field in the `nri.API` struct is set as part of the
[`Register()`](ae7d74b9e2/internal/cri/nri/nri_api_linux.go (L66)) method
* The `nri.Register()` method is only called
[much further down in the CRI `Run()` method](ae71819c4f/pkg/cri/server/service.go (L279))
Signed-off-by: Samuel Karp <samuelkarp@google.com>
NRI is still newer and mostly used by CRI plugin. Keep the package in
internal to allow for interfaces as the project matures.
Signed-off-by: Derek McGowan <derek@mcg.dev>
