There are two approaches for making new versioned CEL features available in the
release where they get introduced:
- Always use the environment for "StoredExpressions".
- Use an older version (typically 1.0) and only bump it up later.
The second approach was used before, so this is now also done here.
Storing a modified claim with allocation and the original resource version in
the assume cache was not reliable: if an update was received, it replaced the
modified claim and the resource that was reserved for the claim might have been
used for some other claim.
To fix this, the in-flight claims are now stored in the map instead of just a
boolean and the status stored there overrides whatever is in the assume cache.
Logging got extended to diagnose this problem better. It started to occur in
E2E tests after splitting the claim update so that first the finalizer is set
and then the status, because setting the finalizer triggered an update.
While currently those objects only get published by the kubelet for node-local
resources, this could change once we also support network-attached
resources. Dropping the "Node" prefix enables such a future extension.
The NodeName in ResourceSlice and StructuredResourceHandle then becomes
optional. The kubelet still needs to provide one and it must match its own node
name, otherwise it doesn't have permission to access ResourceSlice objects.
This adds support for semantic version comparison to the CEL support in the
"named resources" structured parameter model. For example, it can be used to
check that an instance supports a certain API level.
To minimize the risk, the new "semver" type is only defined in the CEL
environment for DRA expressions, not in the base library. See
https://github.com/kubernetes/kubernetes/pull/123664 for a PR which
adds it to the base library.
Validation of semver strings is done with the regular expression from
semver.org. The actual evaluation at runtime then uses semver/v4.
The information is received from the DRA driver plugin through a new gRPC
streaming interface. This is backwards compatible with old DRA driver kubelet
plugins, their gRPC server will return "not implemented" and that can be
handled by kubelet. Therefore no API break is needed.
However, DRA drivers need to be updated because the Go API changed. They can
return
status.New(codes.Unimplemented, "no node resource support").Err()
if they don't support the new ListAndWatchResources method and
structured parameters.
The controller in kubelet then synchronizes this information from the driver
with NodeResourceSlice objects, creating, updating and deleting them as needed.
When allocation was done by the scheduler, the controller needs to do the
deallocation because there is no control-plane controller which could react to
"DeallocationRequested".
If the resource handle has data from a structured parameter model, then we need
to pass that to the DRA driver kubelet plugin. Because Kubernetes uses
gogo/protobuf, we cannot use "optional" for that new optional field and have to
resort to "repeated" with a single repetition if present.
This is a new, backwards-compatible field.
That extending the resource.k8s.io changes the checksum of a kubelet checkpoint
is unfortunate. Updating the test cases is a stop-gap measure, the actual
solution will have to be something else before beta.
Like the current device plugin interface, a DRA driver using this model
announces a list of resource instances. In contrast to device plugins, this
list is made available to the scheduler together with attributes that can be
used to select suitable instances when they are not all alike.
Because this is the first structured parameter model, some checks that
previously were not possible, in particular "is one structured parameter field
set", now gets enabled. Adding another structured parameter model will be
similar.
The applyconfigs code generator assumes that all types in an API are defined in
a single package. If it wasn't for that, it would be possible to place the
"named resources" types in separate packages, which makes their names in the Go
code more natural and provides an indication of their stability level because
the package name could include a version.
When a claim uses structured parameters, as indicated by the resource class
flag, the scheduler is responsible for allocating it. To do this it needs to
gather information about available node resources by watching
NodeResourceSlices and then match the in-tree claim parameters against those
resources.
The kubelet running on one node should not be allowed to access
NodeResourceSlice objects belonging to some other node, as defined by the
NodeResourceSlice.NodeName field.
NodeResourceSlice will be used by kubelet to publish resource information on
behalf of DRA drivers on the node. NodeName and DriverName in
NodeResourceSlice must be immutable. This simplifies tracking the different
objects because what they are for cannot change after creation.
The new field in ResourceClass tells scheduler and autoscaler that they are
expected to handle allocation.
ResourceClaimParameters and ResourceClassParameters are new types for telling
in-tree components how to handle claims.
The assume cache in the volumbinding plugin can be created with no separate
index, but List then failed because it tried to use the empty index name
instead of using the store's List function.
