How does the scheduler find out how many resources are available on a node?

The Scheduler in Kubernetes learns about available resources on a node through the kubelet component, which periodically sends information about the node's status (Node Status) to the API server. This information includes available CPU, memory, disk, and other resources. The Scheduler requests this data from the API server to decide which node to assign a pod to, considering the current load and requested resources.

Thus, the process looks like this:

• kubelet collects metrics and the node's state
• kubelet updates the Node object in the API server with current resources
• The Scheduler reads this data from the API server and makes a decision about pod placement

This allows the scheduler to have up-to-date information about the resources of each node in the cluster.