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Health Check

When configuring the liveness and readiness probes for a cloud host, the process is similar to that of Kubernetes configuration. This article will introduce how to configure health check parameters for a cloud host using YAML.

However, it is important to note that the configuration must be done when the cloud host has been successfully created and is in a powered-off state.

Configuring HTTP Liveness Probe

  1. Configure livenessProbe.httpGet in spec.template.spec.

  2. Modify cloudInitNoCloud to start an HTTP server.

    Click to view YAML example 
    apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  annotations:
    kubevirt.io/latest-observed-api-version: v1
    kubevirt.io/storage-observed-api-version: v1
    virtnest.io/alias-name: ''
    virtnest.io/image-secret: ''
    virtnest.io/image-source: docker
    virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  creationTimestamp: '2024-10-15T02:39:45Z'
  finalizers:
    - kubevirt.io/virtualMachineControllerFinalize
  generation: 1
  labels:
    virtnest.io/os-family: Ubuntu
    virtnest.io/os-version: '22.04'
  name: test-probe
  namespace: amamba-team
  resourceVersion: '254032135'
  uid: 6d92779d-7415-4721-8c7b-a2dde163d758
spec:
  dataVolumeTemplates:
    - metadata:
        creationTimestamp: null
        name: test-probe-rootdisk
        namespace: amamba-team
      spec:
        pvc:
          accessModes:
            - ReadWriteOnce
          resources:
            requests:
              storage: 10Gi
          storageClassName: hwameistor-storage-lvm-hdd
        source:
          registry:
            url: >-
          docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  runStrategy: Halted
  template:
    metadata:
      creationTimestamp: null
    spec:
      architecture: amd64
      domain:
        cpu:
          cores: 1
          sockets: 1
          threads: 1
        devices:
          disks:
            - bootOrder: 1
              disk:
                bus: virtio
              name: rootdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          interfaces:
            - masquerade: {}
              name: default
        machine:
          type: q35
        memory:
          guest: 2Gi
        resources:
          requests:
            memory: 2Gi
      networks:
        - name: default
          pod: {}
      livenessProbe:
        initialDelaySeconds: 120
        periodSeconds: 20
        httpGet:
          port: 1500
        timeoutSeconds: 10
      volumes:
        - dataVolume:
            name: test-probe-rootdisk
          name: rootdisk
        - cloudInitNoCloud:
            userData: |
              #cloud-config
              ssh_pwauth: true
              disable_root: false
              chpasswd: {"list": "root:dangerous", expire: False}
              runcmd:
                - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                - systemctl restart ssh.service
                - dhclient -r && dhclient
                - apt-get update && apt-get install -y ncat
                - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
          name: cloudinitdisk

  3. The configuration of userData may vary depending on the operating system (such as Ubuntu/Debian or CentOS). The main differences are:

    • Package manager:

      Ubuntu/Debian uses apt-get as the package manager. CentOS uses yum as the package manager.

    • SSH service restart command:

      Ubuntu/Debian uses systemctl restart ssh.service. CentOS uses systemctl restart sshd.service (note that for CentOS 7 and earlier versions, it uses service sshd restart).

    • Installed packages:

      Ubuntu/Debian installs ncat. CentOS installs nmap-ncat (because ncat may not be available in the default repository for CentOS).

Configuring TCP Liveness Probe

Configure livenessProbe.tcpSocket in spec.template.spec.

Click to view YAML example configuration 
apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  annotations:
    kubevirt.io/latest-observed-api-version: v1
    kubevirt.io/storage-observed-api-version: v1
    virtnest.io/alias-name: ''
    virtnest.io/image-secret: ''
    virtnest.io/image-source: docker
    virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  creationTimestamp: '2024-10-15T02:39:45Z'
  finalizers:
    - kubevirt.io/virtualMachineControllerFinalize
  generation: 1
  labels:
    virtnest.io/os-family: Ubuntu
    virtnest.io/os-version: '22.04'
  name: test-probe
  namespace: amamba-team
  resourceVersion: '254032135'
  uid: 6d92779d-7415-4721-8c7b-a2dde163d758
spec:
  dataVolumeTemplates:
    - metadata:
        creationTimestamp: null
        name: test-probe-rootdisk
        namespace: amamba-team
      spec:
        pvc:
          accessModes:
            - ReadWriteOnce
          resources:
            requests:
              storage: 10Gi
          storageClassName: hwameistor-storage-lvm-hdd
        source:
          registry:
            url: >-
          docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  runStrategy: Halted
  template:
    metadata:
      creationTimestamp: null
    spec:
      architecture: amd64
      domain:
        cpu:
          cores: 1
          sockets: 1
          threads: 1
        devices:
          disks:
            - bootOrder: 1
              disk:
                bus: virtio
              name: rootdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          interfaces:
            - masquerade: {}
              name: default
        machine:
          type: q35
        memory:
          guest: 2Gi
        resources:
          requests:
            memory: 2Gi
      networks:
        - name: default
          pod: {}
      livenessProbe:
        initialDelaySeconds: 120
        periodSeconds: 20
        tcpSocket:
          port: 1500
        timeoutSeconds: 10
      volumes:
        - dataVolume:
            name: test-probe-rootdisk
          name: rootdisk
        - cloudInitNoCloud:
            userData: |
              #cloud-config
              ssh_pwauth: true
              disable_root: false
              chpasswd: {"list": "root:dangerous", expire: False}
              runcmd:
                - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                - systemctl restart ssh.service
                - dhclient -r && dhclient
                - apt-get update && apt-get install -y ncat
                - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
          name: cloudinitdisk

Configuring Readiness Probes

Configure readiness in spec.template.spec.

Click to view YAML example configuration 
apiVersion: kubevirt.io/v1
kind: VirtualMachine
metadata:
  annotations:
    kubevirt.io/latest-observed-api-version: v1
    kubevirt.io/storage-observed-api-version: v1
    virtnest.io/alias-name: ''
    virtnest.io/image-secret: ''
    virtnest.io/image-source: docker
    virtnest.io/os-image: release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  creationTimestamp: '2024-10-15T02:39:45Z'
  finalizers:
    - kubevirt.io/virtualMachineControllerFinalize
  generation: 1
  labels:
    virtnest.io/os-family: Ubuntu
    virtnest.io/os-version: '22.04'
  name: test-probe
  namespace: amamba-team
  resourceVersion: '254032135'
  uid: 6d92779d-7415-4721-8c7b-a2dde163d758
spec:
  dataVolumeTemplates:
    - metadata:
        creationTimestamp: null
        name: test-probe-rootdisk
        namespace: amamba-team
      spec:
        pvc:
          accessModes:
            - ReadWriteOnce
          resources:
            requests:
              storage: 10Gi
          storageClassName: hwameistor-storage-lvm-hdd
        source:
          registry:
            url: >-
          docker://release-ci.daocloud.io/virtnest/system-images/ubuntu-22.04-x86_64:v1
  runStrategy: Halted
  template:
    metadata:
      creationTimestamp: null
    spec:
      architecture: amd64
      domain:
        cpu:
          cores: 1
          sockets: 1
          threads: 1
        devices:
          disks:
            - bootOrder: 1
              disk:
                bus: virtio
              name: rootdisk
            - disk:
                bus: virtio
              name: cloudinitdisk
          interfaces:
            - masquerade: {}
              name: default
        machine:
          type: q35
        memory:
          guest: 2Gi
        resources:
          requests:
            memory: 2Gi
      networks:
        - name: default
          pod: {}
      readiness:
        initialDelaySeconds: 120
        periodSeconds: 20
        httpGet:
          port: 1500
        timeoutSeconds: 10
      volumes:
        - dataVolume:
            name: test-probe-rootdisk
          name: rootdisk
        - cloudInitNoCloud:
            userData: |
              #cloud-config
              ssh_pwauth: true
              disable_root: false
              chpasswd: {"list": "root:dangerous", expire: False}
              runcmd:
                - sed -i "/#\?PermitRootLogin/s/^.*$/PermitRootLogin yes/g" /etc/ssh/sshd_config
                - systemctl restart ssh.service
                - dhclient -r && dhclient
                - apt-get update && apt-get install -y ncat
                - ["systemd-run", "--unit=httpserver", "ncat", "-klp", "1500", "-e", '/usr/bin/echo -e HTTP/1.1 200 OK\nContent-Length: 12\n\nHello World!']
          name: cloudinitdisk