1. Manual Scale Out Use Case

1.1. Overview

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.

1.1.1. Design Time Diagram

@startuml

title Message Style - Scale Out Sequence Diagram - Design Time

skinparam sequenceMessageAlign center

Participant "Service Designer" as SD
Participant SDC
Participant CLAMP
Participant CDT
Participant APPC
Participant SDNC
Participant Policy
Participant SO
Participant DCAE

SD -> SDC: <back:white>Onboarding Package</back>
SD -> SDC: <back:white>Set Scaling Parameters</back>

SDC -> SO: <back:white>Send Heat Templates and Image Files</back>
SDC -> SDNC: <back:white>Send Heat Templates and Image Files</back>
SDC -> SDNC: <back:white>Send Preload files</back>
SDC -> DCAE: <back:white>Threshold Scaling Events</back>

SD -> CLAMP: <back:white>Gaurd Policies</back>
SD -> CLAMP: <back:white>Operational Policies</back>
SD -> CLAMP: <back:white>Configuration Data</back>

CLAMP -> Policy: <back:white>Send Policies to Policy Engine Including VNF Configuration Data and VF_Module Name</back>

SD -> CDT: <back:white>Parameter definition template for each LCM action (ConfigScaleOut, Healthcheck)</back>

CDT -> APPC: <back:white>Save Parameter Definition Template to APPC</back>

@enduml

Scale Out Sequence Diagram - Design Time

1.1.2. Run Time Diagram

@startuml

title Message Style - Scaling Use Case Sequence Diagram - Run Time

skinparam sequenceMessageAlign center

Participant DCAE
Participant Policy
Participant VID
Participant SO
Participant Controller
Participant SDNC
Participant AAI
Participant VNF

group Manual Scaling
    VID -> SO: Manual Scale Out Request\n(Via DMaaP)
end

group Closed Loop Scaling
    DCAE -> Policy: Trigger Scale Out Event
    activate Policy
    |||
    Policy -> Policy: Sanity Check (Guard Policies)
    |||
    Policy -> SO: <back:white>Closed Loop Scale Out Request</back>
    deactivate Policy
    activate SO
end

group Healthcheck
    SO -> AAI: <back:white>Retrieve VNF Level ipv4-oam-address</back>
    note left
        Prerequisite: Heatbridge will update
        AAI with all IP addresses on initial
        instantiation
    end note
    AAI -> SO: <back:white>Return VNF Level ipv4-oam-address</back>
    |||
    SO -> SO: Controller Look up
    activate Controller
    SO -> Controller: Healthcheck
    Controller -> VNF: Healthcheck (REST)
    deactivate Controller
end

group Instantiation
    SO -> AAI: Create VF-Module in AAI
    note left
        Homing and Capacity is
        not shown in this
        diagram. If H&C check is
        done then SO will call
        OOF prior to calling
        SDNC for resource
        assignment.
    end note
    activate AAI
    deactivate AAI
    SO -> SDNC: <back:white>VF-Module Resource Assignment</back>
    activate SDNC
    SDNC -> SDNC: Heat & Resource Assignment
    |||
    SDNC -> AAI: Create VF-Module Relationship & Retrieve Networks
    deactivate SDNC
    SO -> VNF: <back:white>Create VF_Module in Cloud environment via Heatstack</back>
    note left
        SO will call the Rainy Day
        Handling and/or Manual
        Handling building blocks
        whenever it detects a
        failure in the WorkFlow
    end note
    SO -> AAI: Update the Heatstack ID
end

group Configuration
    SO -> SDNC: <back:white>Request Configuration Parameter Values</back>
    SDNC -> SO: <back:white>Return Configuration Parameter Values</back>
    |||
    SO -> SO: Build ConfigScaleOut Payload
    SO -> SO: Contoller Look up
    SO -> Controller: ConfigScaleOut
    activate Controller
    Controller -> Controller: Construct VNF ScaleOut Request
    Controller -> VNF: Configure VNF (Netconf)
    deactivate Controller
end

group Healthcheck
    SO -> AAI: <back:white>Retrieve VNF Level ipv4-oam-address</back>
    AAI -> SO: <back:white>Return VNF Level ipv4-oam-address</back>
    |||
    SO -> SO: Controller Look up
    activate Controller
    SO -> Controller: Healthcheck
    Controller -> VNF: Healthcheck (REST)
    deactivate Controller
    deactivate SO
end

@enduml

Scaling Use Case Sequence Diagram - Run Time

1.2. 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.

1.3. 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: ONAP Management Requirements.
    1. R-41430 is the requirement dictating the need for VNF Healthchecks.
    2. The health check may be supported using REST, Ansible, or Chef
  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