A Control Loop Type is defined in a TOSCA service template. A TOSCA Service Template has two parts: a definition part in the service template itself, which contains the definitions of concepts that can be used to define the types of concepts that can appear on a Toplogy Template and a Topology Template that defines a topology. See the Oasis Open TOSCA web page for more details on TOSCA.

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The TOSCA concepts above may be declared in the TOSCA Service Template of a control loop. If the concepts already exist in the Design Time Catalogue or the Runtime Inventory, they may be omitted from a TOSCA service template that defines a control loop type.

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1.2.1 Policy Control Loop Element

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The Kubernetes Participant runs Kubernetes Control Loop Elements. Each Kubernetes Control Loop Element manages a Kubernetes microservice using Helm. The user defines the Helm chart for the Kubernetes microservice as well as other properties that the microservice requires in order to execute. The Yaml file that holds the Kubernetes Control Loop Element Type defintion is available in Github and is the canonical definition of the Kubernetes Control Loop Element type. For a description of the Kubernetes Control Loop Element and Kubernetes Participant, please see The CLAMP Kubernetes Participant page.

1.2.4 CDS Control Loop Element

The CDS Participant runs CDS Control Loop Elements. Each CDS Control Loop Element manages the deployment of the CDS blueprint specified in the CDS Control Loop Element definition. The Yaml file that holds the CDS Control Loop Element Type definition is available in Github and is the canonical definition of the CDS Control Loop Element type. For a description of the CDS Control Loop Element and CDS Participant, please see The CLAMP CDS Participant page.

1.2.5 DCAE Participant

The DCAE Participant runs DCAE Control Loop Elements. Each DCAE Control Loop Element manages a DCAE microservice on DCAE. The user defines the DCAE blueprint for the DCAE microservice as well as other properties that the microservice requires in order to execute. The Yaml file that holds the DCAE Control Loop Type definition is available in Github and is the canonical definition of the DCAE Control Loop Element type. For a description of the DCAE Control Loop Element and DCAE Participant, please see The CLAMP DCAE Participant page.

2 Common and Instance Specific Properties

Properties are used to define the configuration for Control Loops and Control Loop Elements. At design time, the types, constraints, and descriptions of the properties are specified. The values for properties are specified in the CLAMP GUI at runtime. TOSCA provides support for defining properties, see Section 3.6.10: TOSCA Property Definition in the TOSCA documentation.

2.1 Terminology for Properties

Property: Metadata defined in TOSCA that is associated with a Control Loop, a Control Loop Element, or a Participant.

TOSCA Property Type: The TOSCA definition of the type of a property. A property can have a generic type such as string or integer or can have a user defined TOSCA data type.

TOSCA Property Value: The value of a Property Type. Property values are assigned at run time in CLAMP.

Common Property Type: Property Types that apply to all instances of a Control Loop Type.

Common Property Value: The value of a Property Type. It is assigned at run time once for all instances of a Control Loop Type.

Instance Specific Property Type: Property Types that apply to an individual instance of a Control Loop Type.

Instance Specific Property Value: The value of a Property Type that applies to an individual instance of a Control Loop Type. The value is assigned at run time for each control loop instance.

Control Loop Properties can be common or instance specific. See Section 2 of TOSCA Defined Control Loops: Architecture and Design for a detailed description of the usage of common and instance specific properties.

2.2 Common Properties

Common properties apply to all instances of a control loop. Common properties are identified by a special metadata flag in Control Loop and Control Loop Element definitions. For example, the startPhase parameter on any Control Loop Element has the same value for any instance of that control loop element, so it is defined as shown below in the Definition of TOSCA fundamental Control Loop Types yaml file.

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2 Common and Instance Specific Properties

Properties are used to define the configuration for Control Loops and Control Loop Elements. At design time, the types, constraints, and descriptions of the properties are specified. The values for properties are specified in the CLAMP GUI at runtime. TOSCA provides support for defining properties, see Section 3.6.10: TOSCA Property Definition in the TOSCA documentation.

2.1 Terminology for Properties

Property: Metadata defined in TOSCA that is associated with a Control Loop, a Control Loop Element, or a Participant.

TOSCA Property Type: The TOSCA definition of the type of a property. A property can have a generic type such as string or integer or can have a user defined TOSCA data type.

TOSCA Property Value: The value of a Property Type. Property values are assigned at run time in CLAMP.

Common Property Type: Property Types that apply to all instances of a Control Loop Type.

Common Property Value: The value of a Property Type. It is assigned at run time once for all instances of a Control Loop Type.

Instance Specific Property Type: Property Types that apply to an individual instance of a Control Loop Type.

Instance Specific Property Value: The value of a Property Type that applies to an individual instance of a Control Loop Type. The value is assigned at run time for each control loop instance.

Control Loop Properties can be common or instance specific. See Section 2 of TOSCA Defined Control Loops: Architecture and Design for a detailed description of the usage of common and instance specific properties.

2.2 Common Properties

Common properties apply to all instances of a control loop. Common properties are identified by a special metadata flag in Control Loop and Control Loop Element definitions. For example, the startPhase parameter on any Control Loop Element has the same value for any instance of that control loop element, so it is defined as shown below in the Definition of TOSCA fundamental Control Loop Types yaml file.

startPhase:
  type: integer
  required: false
  constraints:
  - greater-or-equal: 0
  description: A value indicating the start phase in which this control loop element will be started, the
               first start phase is zero. Control Loop Elements are started in their start_phase order and stopped
               in reverse start phase order. Control Loop Elements with the same start phase are started and
               stopped simultaneously
  metadata:
    common: true

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To create a control loop, a user creates a TOSCA Topology Template. In the Topology Template, the user creates a TOSCA Node Template for each Control Loop Element that will be in the Control Loop Definition. Finally, the user creates the Node Template that defines the Control Loop itself, and references the Control Loop Element definitions that make up the Control Loop Definition.

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The example Gentle Guidance control loop is illustrated in the diagram above. The domain logic for the control loop is implemented in a microservice running in Kubernetes, a policy, a CDS blueprint, and some configuration that is passed to the microservice over a REST endpoint. We want to manage the life cycle of the domain logic for our Gentle Guidance control loop using our TOSCA based Control Loop Life Cycle Management approach. To do this we create four Control Loop Element definitions, one for the Kubernetes microservice, one for the policy , one for the CDS blueprint and one or the REST configuration.

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tosca_definitions_version: tosca_simple_yaml_1_3
topology_template:
  node_templates:
    org.onap.domain.gentleguidance.KubernetesControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.KubernetesControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance Kubernetes Microservice
    org.onap.domain.gentleguidance.RestControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.HttpControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance Microservice REST configuration
    org.onap.domain.gentleguidance.PolicyControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.PolicyControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance Operational Policy
 blueprint
    org.onap.domain.gentleguidance.CdsControlLoopElementDefinitionControlLoopDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.CDSControlLoopElementControlLoop
      type_version: 1.0.1
      description: Control loop elementdefinition for the Gentle Guidance domain
CDS blueprint     org.onap.domain.gentleguidance.ControlLoopDefinitionproperties:
      version  elements:
 1.0.0       type:- org.onap.domain.policygentleguidance.clampKubernetesControlLoopElementDefinition:1.controlloop0.ControlLoop0
       type_version: 1.0.1
      description: Control loop definition for the Gentle Guidance domain
      properties:
        elements:
        -  - org.onap.domain.gentleguidance.KubernetesControlLoopElementDefinitionRestControlLoopElementDefinition:1.0.0
        - org.onap.domain.gentleguidance.RestControlLoopElementDefinitionPolicyControlLoopElementDefinition:1.0.0
        - org.onap.domain.gentleguidance.PolicyControlLoopElementDefinition:1.0.0
        - org.onap.domain.gentleguidance.CdsControlLoopElementDefinition:1.0.0

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The code fragment below shows the TOSCA Topology Template for the Gentle Guidance domain when the default values of  parameters are defined. Please refer to the Yaml file in Github for the definitive Yaml specification.

tosca_definitions_version: tosca_simple_yaml_1_3
topology_template:
  node_templates:
    org.onap.domain.gentleguidance.KubernetesControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.KubernetesControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance Kubernetes Microservice
      properties:
        provider: Ericsson
        participantType: org.onap.policy.controlloop.participant.Kubernetes:1.0.0
        startPhase: 2
        uninitializedToPassiveTimeout: 180
        chart:
            chartId: GentleGuidance:1.0.0
            releaseName: Istanbul
            namespace: org.onap.policy.controlloop.gentleguidance
: tosca_simple_yaml_1_3
topology_template:
  node_templates:
    org.onap.domain.gentleguidance.RestControlLoopElementDefinitionKubernetesControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.HttpControlLoopElementKubernetesControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance Kubernetes Microservice
REST configuration       properties:
        provider: Ericsson
        participantType: org.onap.policy.controlloop.participant.HttpKubernetes:1.0.00
        startPhase: 2
        uninitializedToPassiveTimeout: 180
        startPhasechart:
1            baseUrlchartId: httpsGentleGuidance://101.10.10.10:12345/gentleguidancemicroservice0.0
        httpHeaders:    releaseName: Istanbul
     "Content-Type": "application/json"      namespace: org.onap.policy.controlloop.gentleguidance
   "Accept": "application/json" org.onap.domain.gentleguidance.RestControlLoopElementDefinition:
        configurationEntitiesversion: 1.0.0
      type:   org.onap.policy.clamp.controlloop.gentleguidance.setGentleGuidanceConfig:HttpControlLoopElement
      type_version: 1.0.0:1
      description: Control loop element for the Gentle Guidance Microservice configurationEntityId: org.onap.policy.controlloop.gentleguidance.setGentleGuidanceConfig:1.0.0REST configuration
      properties:
     restSequence:   provider: Ericsson
        - restRequestIdparticipantType: org.onap.policy.controlloop.gentleguidanceparticipant.setGentleGuidanceConfig.CreateGentleHttp:1.0.0
        startPhase: 1
    httpMethd: POST    baseUrl: https://10.10.10.10:12345/gentleguidancemicroservice
        httpHeaders:
          path"Content-Type": "gentleapplication/createjson"
              body:"Accept": "application/json"
        configurationEntities:
       gentleLevel: veryGentle  org.onap.policy.controlloop.gentleguidance.setGentleGuidanceConfig:1.0.0:
              gentleType: softAndFurryconfigurationEntityId: org.onap.policy.controlloop.gentleguidance.setGentleGuidanceConfig:1.0.0
               expectedResponse: 200restSequence:
            - restRequestId: org.onap.policy.controlloop.gentleguidance.setGentleGuidanceConfig.CreateGuidanceCreateGentle:1.0.0
              httpMethd: POST
              path: "guidancegentle/create"
              body:
                guidanceLevel: high           gentleLevel: veryGentle
    guidanceType: subtle           gentleType: softAndFurry
  expectedResponse: 200           org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig:1.0.0:expectedResponse: 200
            - configurationEntityIdrestRequestId: org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfigsetGentleGuidanceConfig.CreateGuidance:1.0.0
              restSequencehttpMethd: POST
           -   restRequestId: org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig.CreateGentle:1.0.0path: "guidance/create"
              httpMethdbody:
 PUT               pathguidanceLevel: "gentle/update]"high
                bodyguidanceType: subtle
               gentleLevel: robustexpectedResponse: 200
          org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig:1.0.0:
            gentleTypeconfigurationEntityId: hardAndGrittyorg.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig:1.0.0
              expectedResponserestSequence: 200
            - restRequestId: org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig.CreateGuidanceCreateGentle:1.0.0
              httpMethd: PUT
              path: "guidancegentle/update]"
              body:
                guidanceLevelgentleLevel: lowrobust
                guidanceTypegentleType: tersehardAndGritty
              expectedResponse: 200
    org.onap.domain.gentleguidance.PolicyControlLoopElementDefinition:        - versionrestRequestId: org.onap.policy.controlloop.gentleguidance.updateGentleGuidanceConfig.CreateGuidance:1.0.0
      type: org.onap.policy.clamp.controlloop.PolicyControlLoopElement       type_version: 1.0.1
httpMethd: PUT
     description: Control loop element for the Gentle Guidance Operational Policy
path: "guidance/update"
     properties:         providerbody:
Ericsson             participantType: org.onap.policy.controlloop.participant.Policy:1.0.0  guidanceLevel: low
     startPhase: 0         policyType: onap.policies.controlloop.operational.common.Apex:1.0.0 guidanceType: terse
              policyIdexpectedResponse: org.onap.domain.gentleguidance.policy.GentleGuidanceAssertive:1.0.0200
    org.onap.domain.gentleguidance.CdsControlLoopElementDefinitionPolicyControlLoopElementDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.CDSControlLoopElementPolicyControlLoopElement
      type_version: 1.0.1
      description: Control loop element for the Gentle Guidance CDSOperational blueprintPolicy
      properties:
        provider: Ericsson
        participantType: org.onap.policy.controlloop.participant.CdsPolicy:1.0.0
         startPhase: startPhase: 0
        policyType: onap.policies.controlloop.operational.common.Apex:1.0.0
        cdsBlueprint: "Placeholder for the CDS blueprint"policyId: org.onap.domain.gentleguidance.policy.GentleGuidanceAssertive:1.0.0
     org.onap.domain.gentleguidance.ControlLoopDefinition:
      version: 1.0.0
      type: org.onap.policy.clamp.controlloop.ControlLoop
      type_version: 1.0.1
      description: Control loop definition for the Gentle Guidance domain
      properties:
        provider: Ericsson
        elements:
        - org.onap.domain.gentleguidance.KubernetesControlLoopElementDefinition:1.0.0
        - org.onap.domain.gentleguidance.RestControlLoopElementDefinition:1.0.0
        - org.onap.domain.gentleguidance.PolicyControlLoopElementDefinition:1.0.0
     
  - org.onap.domain.gentleguidance.CdsControlLoopElementDefinition:1.0.0

4. Creating Custom Control Loop Elements

Any organization can include their own component in the framework and use the framework and have the Policy Framework CLAMP manage the lifecycle of domain logic in their component as part of a Control Loop. To do this, a participant for the component must be developed that allows Control Loop Elements for that component to be run. To develop a participant, the participant must comply with the CLAMP Participants framework and in particular comply with The CLAMP Control Loop Automation Composition Participant Protocol. The organization must also specify a new Control Loop Element type definition in TOSCA similar to those supplied in ONAP and described in Section 1.2. This Control Loop Element type tells the CLAMP Control Loop Lifecycle management that the Control Loop Element exists and can be included in control loops. It also specifies the properties that can be specified for the Control Loop Element.

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