Kubernetes scheduler will usually run at every master node, but that might not be the case. It could be executed as a host process or an in-cluster pod.
If host process (for example, systemd), metricbeat should be running at that same node gathering data from the scheduler.
If executing as a pod:
A metricbeat instance can be also executed using the same affinity and deployment object (deployment, daemonset, ...) as the kubernetes scheduler.
A metricbeat instance can be launched as a sidecar container