You are viewing documentation for a release that is no longer supported. The latest supported version of version 3 is [3.11]. For the most recent version 4, see [4]
You are viewing documentation for a release that is no longer supported. The latest supported version of version 3 is [3.11]. For the most recent version 4, see [4]

Use this procedure to create liveness and readiness probes to monitor virtual machine health.

About liveness and readiness probes

When a VirtualMachineInstance (VMI) fails, liveness probes stop the VMI. Controllers such as VirtualMachine then spawn other VMIs, restoring virtual machine responsiveness.

Readiness probes tell services and endpoints that the VirtualMachineInstance is ready to receive traffic from services. If readiness probes fail, the VirtualMachineInstance is removed from applicable endpoints until the probe recovers.

Define an HTTP liveness probe

This procedure provides an example configuration file for defining HTTP liveness probes.

Procedure
  1. Customize a YAML configuration file to create an HTTP liveness probe, using the following code block as an example. In this example:

    • You configure a probe using spec.livenessProbe.httpGet, which queries port 1500 of the VirtualMachineInstance, after an initial delay of 120 seconds.

    • The VirtualMachineInstance installs and runs a minimal HTTP server on port 1500 using cloud-init.

      apiVersion: kubevirt.io/v1alpha3
      kind: VirtualMachineInstance
      metadata:
        labels:
          special: vmi-fedora
        name: vmi-fedora
      spec:
        domain:
          devices:
            disks:
            - disk:
                bus: virtio
              name: containerdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          resources:
            requests:
              memory: 1024M
        livenessProbe:
          initialDelaySeconds: 120
          periodSeconds: 20
          httpGet:
            port: 1500
          timeoutSeconds: 10
        terminationGracePeriodSeconds: 0
        volumes:
        - name: containerdisk
          registryDisk:
            image: kubevirt/fedora-cloud-registry-disk-demo
        - 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: cloudinitdisk
  2. Create the VirtualMachineInstance by running the following command:

    $ oc create -f <file name>.yaml

Define a TCP liveness probe

This procedure provides an example configuration file for defining TCP liveness probes.

Procedure
  1. Customize a YAML configuration file to create an TCP liveness probe, using this code block as an example. In this example:

    • You configure a probe using spec.livenessProbe.tcpSocket, which queries port 1500 of the VirtualMachineInstance, after an initial delay of 120 seconds.

    • The VirtualMachineInstance installs and runs a minimal HTTP server on port 1500 using cloud-init.

      apiVersion: kubevirt.io/v1alpha3
      kind: VirtualMachineInstance
      metadata:
        labels:
          special: vmi-fedora
        name: vmi-fedora
      spec:
        domain:
          devices:
            disks:
            - disk:
                bus: virtio
              name: containerdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          resources:
            requests:
              memory: 1024M
        livenessProbe:
          initialDelaySeconds: 120
          periodSeconds: 20
          tcpSocket:
            port: 1500
          timeoutSeconds: 10
        terminationGracePeriodSeconds: 0
        volumes:
        - name: containerdisk
          registryDisk:
            image: kubevirt/fedora-cloud-registry-disk-demo
        - 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: cloudinitdisk
  2. Create the VirtualMachineInstance by running the following command:

    $ oc create -f <file name>.yaml

Define a readiness probe

This procedure provides an example configuration file for defining readiness probes.

Procedure
  1. Customize a YAML configuration file to create a readiness probe. Readiness probes are configured in a similar manner to liveness probes. However, note the following differences in this example:

    • Readiness probes are saved using a different spec name. For example, you create a readiness probe as spec.readinessProbe instead of as spec.livenessProbe.<type-of-probe>.

    • When creating a readiness probe, you optionally set a failureThreshold and a successThreshold to switch between ready and non-ready states, should the probe succeed or fail multiple times.

      apiVersion: kubevirt.io/v1alpha3
      kind: VirtualMachineInstance
      metadata:
        labels:
          special: vmi-fedora
        name: vmi-fedora
      spec:
        domain:
          devices:
            disks:
            - disk:
                bus: virtio
              name: containerdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          resources:
            requests:
              memory: 1024M
        readinessProbe:
          httpGet:
            port: 1500
          initialDelaySeconds: 120
          periodSeconds: 20
          timeoutSeconds: 10
          failureThreshold: 3
          successThreshold: 3
        terminationGracePeriodSeconds: 0
        volumes:
        - name: containerdisk
          registryDisk:
            image: kubevirt/fedora-cloud-registry-disk-demo
        - 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: cloudinitdisk
  2. Create the VirtualMachineInstance by running the following command:

    $ oc create -f <file name>.yaml