Hypervisor

Source Code

github.com/cobaltcore-dev/openstack-hypervisor-operator

The hypervisor is the bare metal node that runs virtual machines. CobaltCore manages hypervisors through a set of Kubernetes operators and containerized agents that handle configuration, health reporting, and VM lifecycle - without requiring direct access to the node.

Component stack

Each hypervisor node runs the following components on top of GardenLinux:

Agent	Role
Node Agent	Manages node lifecycle and exposes hardware state to Kubernetes
Nova Agent	Handles compute scheduling and VM creation via libvirt
Neutron Agent	Manages VM network interfaces via OVN/OVS
HA Agent	Monitors libvirt events and reports telemetry to the HA Service

Interactions

Components communicate through Unix domain sockets or TCP. Key system dependencies:

KVM Node Agent

Source Code

github.com/cobaltcore-dev/kvm-node-agent

The Node Agent runs on each hypervisor and exposes the node's hardware state and VM inventory to the Kubernetes API through two CRDs:

hypervisors.kvm.cloud.sap

Represents a hypervisor node. Tracks hardware model, CPU/memory topology, GardenLinux version, running VMs, and systemd service status.

$ kubectl get hypervisors.kvm.cloud.sap
NAME            NODE            VERSION               INSTANCES   HARDWARE               KERNEL          AGE
node001-bb234   node001-bb234   Garden Linux 1933.0   11          PowerEdge R860         6.12.38-amd64   4d8h
node006-bb123   node006-bb123   Garden Linux 1933.0   0           ProLiant DL560 Gen11   6.12.38-amd64   27h

See the API Reference for the full spec.

migrations.kvm.cloud.sap

Tracks live migration operations between hypervisors - source, destination, progress (data transferred, memory iteration, elapsed time).

$ kubectl get migrations.kvm.cloud.sap
NAME                                   ORIGIN          DESTINATION     TYPE        OPERATION       STARTED   ELAPSED     DATA TOTAL
12e479eb-6bef-4fdb-bfdc-0388df68bed9   node002-bb086   node008-bb086   completed   migration_in    74d       2.755s      4.0 GiB
1552e60a-bdba-4850-84da-07dd635bce2c   node006-bb086   node003-bb087   completed   migration_out   22d       35.078s     64.0 GiB

See the API Reference for the full spec.

KVM HA Agent

Source Code

github.com/cobaltcore-dev/kvm-ha-agent

The HA Agent subscribes to libvirt domain events and periodically reports instance state and host uptime to the central HA Service. The HA Service uses this telemetry to detect unhealthy nodes and trigger evacuation.

Monitored libvirt events include: lifecycle changes, reboots, watchdog triggers, I/O errors, control errors, agent lifecycle, and memory failures.