Liveness Probes will effectively stop the VirtualMachineInstance if they
fail, which will allow higher level controllers, like VirtualMachine or
VirtualMachineInstanceReplicaSet to spawn new instances, which will
hopefully be responsive again.
Readiness Probes are an indicator for Services and Endpoints if the
VirtualMachineInstance is ready to receive traffic from Services. If
Readiness Probes fail, the VirtualMachineInstance will be removed from
the Endpoints which back services until the probe recovers.
Define a HTTP Liveness Probe
The following VirtualMachineInstance configures a HTTP Liveness Probe
via spec.livenessProbe.httpGet, which will query port 1500 of the
VirtualMachineInstance, after an initial delay of 120 seconds. The
VirtualMachineInstance itself installs and runs a minimal HTTP server on
port 1500 via cloud-init.
apiVersion: kubevirt.io/v1alpha2
kind: VirtualMachineInstance
metadata:
labels:
special: vmi-fedora
name: vmi-fedora
spec:
domain:
devices:
disks:
- disk:
bus: virtio
name: registrydisk
volumeName: registryvolume
- disk:
bus: virtio
name: cloudinitdisk
volumeName: cloudinitvolume
resources:
requests:
memory: 1024M
livenessProbe:
initialDelaySeconds: 120
periodSeconds: 20
httpGet:
port: 1500
timeoutSeconds: 10
terminationGracePeriodSeconds: 0
volumes:
- name: registryvolume
registryDisk:
image: registry:5000/kubevirt/fedora-cloud-registry-disk-demo:devel
- cloudInitNoCloud:
userData: |-
#cloud-config
password: fedora
chpasswd: { expire: False }
bootcmd:
- setenforce 0
- dnf install -y nmap-ncat
- systemd-run --unit=httpserver nc -klp 1500 -e '/usr/bin/echo -e HTTP/1.1 200 OK\\n\\nHello World!'
name: cloudinitvolume
Define a TCP Liveness Probe
The following VirtualMachineInstance configures a TCP Liveness Probe via
spec.livenessProbe.tcpSocket, which will query port 1500 of the
VirtualMachineInstance, after an initial delay of 120 seconds. The
VirtualMachineInstance itself installs and runs a minimal HTTP server on
port 1500 via cloud-init.
apiVersion: kubevirt.io/v1alpha2
kind: VirtualMachineInstance
metadata:
labels:
special: vmi-fedora
name: vmi-fedora
spec:
domain:
devices:
disks:
- disk:
bus: virtio
name: registrydisk
volumeName: registryvolume
- disk:
bus: virtio
name: cloudinitdisk
volumeName: cloudinitvolume
resources:
requests:
memory: 1024M
livenessProbe:
initialDelaySeconds: 120
periodSeconds: 20
tcpSocket:
port: 1500
timeoutSeconds: 10
terminationGracePeriodSeconds: 0
volumes:
- name: registryvolume
registryDisk:
image: registry:5000/kubevirt/fedora-cloud-registry-disk-demo:devel
- cloudInitNoCloud:
userData: |-
#cloud-config
password: fedora
chpasswd: { expire: False }
bootcmd:
- setenforce 0
- dnf install -y nmap-ncat
- systemd-run --unit=httpserver nc -klp 1500 -e '/usr/bin/echo -e HTTP/1.1 200 OK\\n\\nHello World!'
name: cloudinitvolume
Define Readiness Probes
Readiness Probes are configured in a similar way like liveness probes.
Instead of spec.livenessProbe, spec.readinessProbe needs to be
filled:
apiVersion: kubevirt.io/v1alpha2
kind: VirtualMachineInstance
metadata:
labels:
special: vmi-fedora
name: vmi-fedora
spec:
domain:
devices:
disks:
- disk:
bus: virtio
name: registrydisk
volumeName: registryvolume
- disk:
bus: virtio
name: cloudinitdisk
volumeName: cloudinitvolume
resources:
requests:
memory: 1024M
readinessProbe:
httpGet:
port: 1500
initialDelaySeconds: 120
periodSeconds: 20
timeoutSeconds: 10
failureThreshold: 3
successThreshold: 3
terminationGracePeriodSeconds: 0
volumes:
- name: registryvolume
registryDisk:
image: registry:5000/kubevirt/fedora-cloud-registry-disk-demo:devel
- cloudInitNoCloud:
userData: |-
#cloud-config
password: fedora
chpasswd: { expire: False }
bootcmd:
- setenforce 0
- dnf install -y nmap-ncat
- systemd-run --unit=httpserver nc -klp 1500 -e '/usr/bin/echo -e HTTP/1.1 200 OK\\n\\nHello World!'
name: cloudinitvolume
Note that in the case of Readiness Probes, it is also possible to set a
failureThreshold and a successThreashold to only flip between ready
and non-ready state if the probe succeeded or failed multiple times.
