volcano/docs/design/node-priority.md

Node Priority in Kube-Batch

This feature allows kube-batch to schedule workloads based on the priority of the Nodes, Workloads will be scheduled on Nodes with higher priority and these priorities will be calculated based on different parameters like ImageLocality, Most/Least Requested Nodes...etc. A basic flow for the Node priority functions is depicted below.

Currently in kube-batch Session is opened every 1 sec and the workloads which are there in Queue goes through Predicate to find a suitable set of Nodes where workloads can be scheduled and after that it goes through Allocate function to assign the Pods to the Nodes and then goes to Preempt if applicable.

Node Priority can be introduced in the current flow for Allocate and Preempt function. Once we have set of Nodes where we can scheduled the workloads then flow will go through Prioritize function which will do the following things :

• Run all the priority functions on all the list Nodes which is given by Predicate function in a parallel go-routine.
• Score the Node based on whether the Priority Rule satisfies the Workload scheduling criteria.
• Once the scores are returned from all the PriorityFn then aggregate the scoring and identify the Node with highest scoring.
• Delegate this selected Node in last step to AllocateFn to Bind the workload to the Node.

Currently there are multiple PriorityFn available with default Scheduler of Kubernetes. Going forward with each release we will implement all the priority functions in kube-batch based on their importance to batch scheduling.