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vm_cluster_expansion_guide.md

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VM cluster expansion guide

VM cluster expansion means that we can add additional vm-work node(s) to existing VM cluster. They can be added on any existing vm_host machines or new vm_host machine(s) can be added as well. By default VM cluster expansion feature won't re-create existing VMs, which are in 'running' state. They will remain untouched during VM creation phase, nevertheless standard ansible deployment tasks will run on them as well. Corresponding ansible playbooks should be idempotent to ensure that running tasks again won't corrupt target system. Group vars for VM case contain new variable vm_recreate_existing with value set to false. In order to expand VM cluster, the original VM cluster have to be up and running.

vm_recreate_existing: false

For VM cluster expansion deployment we should use the same ansible host, which was used for original VM cluster deployment. Deployment configuration can't be changed except adding definitions for new VMs. Configuration of existing VMs have to remain the same.

NOTE: If you want to add new vm-work node to existing vm_host then the vm_host needs to have enough free available resources for it.

NOTE: VM cluster expansion deployment is not intended for any kind of configuration update on existing VMs.

NOTE: VM cluster reduction - removing vm-work node(s) from VM cluster - is not supported at all.

Adding new vm-work to existing vm_host

To add new vm-work to existing vm-host you need to update vms definition in host_vars file for corresponding vm_host. In example bellow we've added new vm-work node definition with name vm-work-4

vms:
  ...
  ...
  ...
  - type: "work"
    name: "vm-work-4"
    cpu_total: 16
    memory: 20480
    vxlan: 128
    pci:
      - "18:02.0"
      - "18:02.1"
      - "18:02.6"
      - "18:02.7"
      - "b1:01.3"
      - "b3:01.3"
# Or in case with auto-configuration of SRIOV NIC and SRIOV QAT
  - type: "work"
    name: "vm-work-4"
    cpu_total: 16
    memory: 20480
    vxlan: 128
    pci: []
    nic_devices_count: 4
    qat_devices_count: 2

New host_vars file needs to be created for added vm-work node. In our case host_vars/vm-work-4.yml. Existing host_vars/vm-work-1.yml can be used as a template.

Adding new vm_host machine with new vm-work

To add new vm_host machine you need to follow point 6 and point 8 in README To be more precise we need to do three steps:

  1. add new vm_host to inventory
  • Add vm_host info to section [all]
  • Add vm_host name to the end of section [vm_host]
  1. create host_vars file for that vm_host from template host_vars/host-for-vms-2.yml
  • Update host specific params like dataplane_interfaces and qat_devices
  • Fill vms section with new vm-work node(s)
  1. create new host_vars file for added vm-work node. In our case host_vars/vm-work-5.yml. Existing host_vars/vm-work-1.yml can be used as a template.
vms:
  - type: "work"
    name: "vm-work-5"
    cpu_total: 16
    memory: 20480
    vxlan: 128
    pci:
      - "18:02.0"
      - "18:02.1"
      - "18:02.6"
      - "18:02.7"
      - "b1:01.3"
      - "b3:01.3"
# Or in case with auto-configuration of SRIOV NIC and SRIOV QAT
  - type: "work"
    name: "vm-work-5"
    cpu_total: 16
    memory: 20480
    vxlan: 128
    pci: []
    nic_devices_count: 4
    qat_devices_count: 2

Run VM cluster expansion deployment

Once we have prepared configuration for new VMs, we can run deployment via following command:

ansible-playbook -i inventory.ini playbooks/vm.yml -e scale=true
or
ansible-playbook -i inventory.ini playbooks/vm.yml -e scale=true --flush-cache -vv 2>&1 | tee vm_cluster_expansion.log

Other options

If you want to update VM cluster including current VMs then vm_recreate_existing parameter can be switched to true In that case all existing VMs will be destroyed and re-created again.

NOTE: All data, configurations and logs stored on VMs will be lost. Re-created VMs will get new IPs. NOTE: If vm_recreate_existing is set to true then following two lists vm_recreate_listed_vms and vm_keep_listed_vms are not evaluated.

vm_recreate_existing: true

If you want to update just specific VM(s) then keep vm_recreate_existing parameter on false and use another configuration parameter vm_recreate_listed_vms and insert VM names, which should be re-created, there. Default value for this paramater is empty list []

vm_recreate_listed_vms: []

VMs to be re-created should be provided as list items E.g.:

vm_recreate_listed_vms:
  - vm-work-2
  - vm-1

If you want to keep existing VM, which is not in running state untouched from any reason then keep vm_recreate_existing parameter on false and use another configuration parameter vm_keep_listed_vms and insert VM names, which should be kept, there. Default value for this paramater is empty list []

vm_keep_listed_vms: []

VMs to be kept should be provided as list items E.g.:

vm_keep_listed_vms:
  - vm-work-3
  - vm-1

NOTE: If the same VM name appears in both lists vm_recreate_listed_vms and vm_keep_listed_vms then vm_keep_listed_vms has precedence and VM will be kept. NOTE: Deployment procedure tries to start not running VMs, which were kept. Nevertheless subsequent ansible plays can fail if VM start was not successful or if they are in some inconsistent state.

To run those options use following command:

ansible-playbook -i inventory.ini playbooks/vm.yml
or
ansible-playbook -i inventory.ini playbooks/vm.yml --flush-cache -vv 2>&1 |tee vm_cluster_recreate.log