VNF scaling¶

TOSCA schema for scaling policy¶

Tacker defines TOSCA schema for the scaling policy as given below:

tosca.policies.tacker.Scaling:
  derived_from: tosca.policies.Scaling
  description: Defines policy for scaling the given targets.
  properties:
    increment:
      type: integer
      required: true
      description: Number of nodes to add or remove during the scale out/in.
    min_instances:
      type: integer
      required: true
      description: Minimum number of instances to scale in.
    max_instances:
      type: integer
      required: true
      description: Maximum number of instances to scale out.
    default_instances:
      type: integer
      required: true
      description: Initial number of instances.
    cooldown:
      type: integer
      required: false
      default: 120
      description: Wait time (in seconds) between consecutive scaling
      operations. During the cooldown period, scaling action will be ignored
  targets:
    type: list
    entry_schema:
      type: string
    required: true
    description: List of Scaling nodes.

Sample TOSCA with scaling policy¶

Following TOSCA snippet shows the scaling policy used in VNFD, in which vdu1 and vdu2 are already defined VDUs.

policies:

  - sp1:

      type: tosca.policies.tacker.Scaling

      description: Simple VDU scaling

      targets: [vdu1, vdu2]

      properties:
        min_instances: 1

        max_instances: 3

        default_instances: 2

        increment: 1

Deploying scaling TOSCA template using Tacker¶

Once OpenStack/Devstack along with Tacker has been successfully installed, deploy a sample scaling template from location given below: https://github.com/openstack/tacker/tree/master/samples/tosca-templates/vnfd

Refer the ‘Getting Started’ link below on how to create a VNFD and deploy a VNF: https://docs.openstack.org/tacker/latest/install/getting_started.html

How to scale VNF using CLI¶

Tacker provides following CLI for scaling.

openstack vnf scale –vnf-id <vnf-id>

–vnf-name <vnf name> –scaling-policy-name <policy name> –scaling-type <type>

Here,

• scaling-policy-name - Policy name defined in scaling VNFD
• scaling-type - in or out
• vnf-id - scaling VNF id
• vnf-name - scaling VNF name

For example, to scale-out policy ‘sp1’ defined above, this cli could be used as below:

openstack vnf scale –vnf-name sample-vnf

–scaling-policy-name sp1 –scaling-type out

How to scale VNF using REST API¶

Tacker provides following REST API for scaling.

POST on v1.0/vnfs/<vnf-id>/actions

with body

{“scale”: { “type”: “<type>”, “policy” : “<scaling-policy-name>”}}

Here,

• scaling-policy-name - Policy name defined in scaling VNFD
• scaling-type - in or out
• vnf-id - scaling VNF id

Response http status codes:

• 202 - Accepted the request for doing the scaling operation
• 404 - Bad request, if given scaling-policy-name and type are invalid
• 500 - Internal server error, on scaling operation failed due to an error
• 401 - Unauthorized

VNF state transitions during scaling operation¶

During the scaling operation, the VNF will be moving in below state transformations:

• ACTIVE -> PENDING_SCALE_IN -> ACTIVE
• ACTIVE -> PENDING_SCALE_IN -> ERROR
• ACTIVE -> PENDING_SCALE_OUT -> ACTIVE
• ACTIVE -> PENDING_SCALE_OUT -> ERROR

Limitations¶

Following features are not supported with scaling:

• Auto-scaling feature is supported only with alarm monitors and it does not work with other monitors such as ping, http_ping.
• When VNF is modelled with scaling requirement in VNFD, any config management requirement in VNFD is not supported.
• Scaling feature does not support to selectively choose the VDU as part of scaling.