The Pod Scheduling Process

The scheduler works in a three-step process: filtering, scoring, and assigning. Let's take a look at what happens during the execution of each of these steps. An overview of the process is described in the following diagram:

Figure 17.1: An overview of how the Kubernetes Scheduler selects a suitable node

Filtering

Filtering is a process in which the Kubernetes Scheduler runs a series of checks or filters to see which nodes are not suitable to run the target Pod. An example of a filter is to see if the node has enough CPU and memory to host the Pod, or if the storage volume requested by the Pod can be mounted on the host. If the cluster has no node that's suitable to meet the requirements of the Pod, then the Pod is deemed un-schedulable and is not executed on the cluster.

Scoring

Once the Kubernetes Scheduler has a list of feasible nodes, the second step is to score the nodes and find the best node(s) to host the...