YuniKorn Concepts

Internal

• YuniKorn

YuniKorn Core

YuniKorn Core Concepts

Kuberentes Implementation

• A namespace can have a "queue" if annotated with "yunikorn.apache.org/queue". A namespace can have a "parent queue" is annotated with "yunikorn.apache.org/parentqueue".
• An allocation can be in one of two states ("Pending" and "In-Progress"). A pending allocation is one which has been decided upon by YuniKorn but has not yet been communicated to the default scheduler via PreFilter()/Filter(). Once PreFilter()/Filter() pass, the allocation transitions to "In-Progress" to signify that the default scheduler is responsible for fulfilling the allocation. Once PostBind() is called in the plugin to signify completion of the allocation, it is removed.
• When a new pod annotated with schedulerName: yunikorn needs scheduling, the API server (admission controller (?)) calls the "admission-webhook.yunikorn.mutate-pods" webhook with a POST https://yunikorn-admission-controller-service.yunikorn.svc:443/mutate?timeout=10s. Service "yunikorn-admission-controller-service". When running locally, the service does not get deployed, yet the pods get scheduled. This is how: there's a Kubernetes mechanism involving "informers" that periodically updates the state of the resources is interested in. There are "update", "add" and "delete" notifications. When a new pod shows up, general.Manager.AddPod() is invoked, which creates and Application and Task using the pod metadata → PodEventHandler.addPod() → cache.Context.AddApplication(). At the same time, there's the main KubernetesShim scheduling loop that finds the new application and so the scheduling process begins.