As the foundation of cloud-bursting, users can work with built-in metrics for VMs and scaling groups. See VM monitoring and metrics.
For physical datacenters, we gather some metrics from KVM and there’s a collectd plugin for vCenter.
Users can also work with custom metrics throughout the cloud, i.e. for VMs, scaling groups, virtual appliances, virtual datacenters, machines, racks, datacenters, and public cloud regions, using the API. See Custom Metrics Resources
The endpoints for custom metrics also support collectd format. See Use collectd plugin for custom metrics