Manual Scale Out Use Case

In the Casablanca release, ONAP will support the ability to both manually and automatically scale out a VNF component. Below is the sequence diagram for how scaling will work.



Description of Workflow

At a high level the way Scale Out will work is:

  1. VF_Modules (VNFC’s) may be scaled out with either one of two methods:

    1. Using VID, the operator will choose to scale out a VNFC by picking a VF_Module to scale

    2. An operator may define an operating policy (and associated guard policies) to trigger a scaling operation automatically.

      • As an example, the operating policy may be when the output of an application load balancer crosses a bandwidth threshold, then increase the number of instances of the application.

      • Examples of a guard policies:

        1. If a scaling operation has run within the past X minutes, then do not scale.
        2. If the number of instance is <= MIN_INSTANCES or >= MAX_INSTANCES, then do not scale.
  2. VID or Policy sends the Scale Out Request to SO.

  3. When SO receives the Scaling request it will first send a request to the appropriate controller (APPC or SDNC) to execute a health check on the VNF.

  4. Once the health check has been run, SO executes the Heat Template associated with the VF Module requested by the VID Operator or the operational policy.

  5. After the new component(s) have been instantiated SO calls the responsible controller (via DMaaP) to configure the new instances using Ansible, Chef, or Netconf.

  6. Finally a health check is run to ensure that the entire VNF is Operating as it should.

VNF Impacts

For VNFs to make use of the Manual Scaling Capabilities of ONAP, they must support the following functionality:

  1. VNFs must support a Healthcheck as described in: The Management Section of the ONAP VNF Guidelines.
    1. R-41430 is the requirement dictating the need for VNF Healthchecks.
    2. The health check may be supported using REST, Ansible, or Chef
      • REST health check requirements can be found in the vnf_rest_apis
      • The Ansible health check playbook can be found in the ansible_playbook_requirements
  2. R-43413 states that a “VNF MUST utilize a modular Heat Orchestration Template design to support scaling”. The description of this design may be found in the ONAP VNF Modularity Overview of the Heat Requirements.
    1. The VF_Module to be scaled must be built according to the VNF Modularity Rules for Incremental Modules
  3. Configuration of the VNF must be done via NETCONF, Chef, or Ansible as described in the Configuration Management