Use cases
A new module is added to the cluster
The operator lists all nodes required to build the module and looks at their kernels. It uses the Module’s .spec.kernelMappings to create DaemonSets for each of those kernels.
If an image for one of these DaemonSets requires an in-cluster build, it creates the build object (build system TBD).
The Module owns the build object, so that it is deleted when the Module is deleted.
Module update: kernel $kernel should run a new DriverContainer image
The OOTO would be triggered by an update to any Module instance.
That reconciliation generates a list of DaemonSets that need to be reconciled.
For each DaemonSet belonging to Module, we set the following labels:
| key | value |
|---|---|
kmm.node.kubernetes.io/module.name |
$moduleName |
kmm.node.kubernetes.io/kernel-version.full |
$kernel |
We either create those DaemonSets (if they do not already exist) or update them (if a DaemonSet already exists with
the same labels).
If a DaemonSet already exists for $moduleName and $kernel, it is updated with the new DriverContainer image.
If that image requires a build, we create the build object and wait for its completion before we modify the DaemonSet.
A new node joins the cluster (or is modified)
The OOTO lists all Modules and checks which ones should run on the node.
For each Module that should run on the node (determined by the .spec.selector field), the operator tries to find a suitable DriverContainer image for the node’s kernel.
It creates a DaemonSet that runs that DriverContainer on all nodes running that kernel.
A node leaves the cluster
If that node was targeted by one of the DaemonSets, said DaemonSet’s .status.desiredNumberScheduled is decremented.
The operator watches changes to those objects; if that field reaches 0, the DaemonSet is deleted.
A node’s kernel is updated
Depending on the Kubernetes distribution used, this is functionally equivalent to either:
- Deleting the node and creating a new one, or;
- Modifying an existing node.
That use case is thus covered above.
A node matches a Module’s .spec.selector, but not any of its kernel mappings
No DaemonSet is scheduled for this module and this kernel. The OOT kernel module will not be deployed on that node.