The CLAMP Control Loop Participant Protocol

The CLAMP Control Loop Participant protocol is an asynchronous protocol that is used by the CLAMP runtime to coordinate life cycle management of Control Loop instances. The protocol supports the functions described in the sections below.

Protocol Dialogues

The protocol supports the dialogues described below.

Participant Registration and De-Registration

Registration when a participant comes up and update of participant with control loop type information and common parameter values for its control loop types.

De-registration is executed as a participant goes down.

Control Loop Priming and De-Priming

When a control loop is primed, the portion of the Control Loop Type Definition and Common Property values for the participants of each participant type mentioned in the Control Loop Definition are sent to the participants.

When a control loop is de-primed, the portion of the Control Loop Type Definition and Common Property values for the participants of each participant type mentioned in the Control Loop Definition are deleted on participants.

Control Loop Update

Control Loop Update handles creation, change, and deletion of control loops on participants. Change of control loops uses a semantic versioning approach and follow the semantics described on the page 4.1 Management of Control Loop Instance Configurations <management-cl-instance-configs>.

The handling of a ControlLoopUpdate message in each participant is as shown below.

Control Loop State Change

This dialogue is used to change the state of Control Loops and their Control Loop Elements. The CLAMP Runtime sends a Control Loop State Change message on the control loop to all participants. Participants that have Control Loop Elements in that Control Loop attempt an update on the state of the control loop elements they have for that control loop, and report the result back.

The startPhase in the Definition of TOSCA fundamental Control Loop Types is particularly important in control loop state changes because sometime the user wishes to control the order in which the state changes in Control Loop Elements in a control loop. In state changes from UNITITIALISED → PASSIVE and from PASSIVE → RUNNING, control loop elements are started in increasing order of their startPhase. In state changes from RUNNING → PASSIVE and from PASSIVE → UNITITIALISED, control loop elements are started in decreasing order of their startPhase.

The CLAMP runtime controls the state change process described in the diagram below. The CLAMP runtime sends a Control Loop State Change message on DMaaP to all participants in a particular Start Phase so, in each state change multiple Control Loop State Change messages are sent, one for each Start Phase in the control loop. If more than one Control Loop Element has the same Start Phase, those Control Loop Elements receive the same Control Loop State Change message from DMaaP and start in parallel.

The Participant reads each State Change Message it sees on DMaaP. If the Start Phase on the Control Loop State Change message matches the Start Phase of the Control Loop Element, the participant processes the State Change message. Otherwise the participant ignores the message.

The handling of a ControlLoopStateChange message in each participant is as shown below.

Control Loop Monitoring and Reporting

This dialogue is used as a heartbeat mechanism for participants, to monitor the status of Control Loop Elements, and to gather statistics on control loops. The ParticipantStatus message is sent periodically by each participant. The reporting interval for sending the message is configurable.

Messages

The CLAMP Control Loop Participant Protocol uses the following messages. The descriptions below give an overview of each message. For the precise definition of the messages, see the CLAMP code at Github . All messages are carried on DMaaP.

Message	Source	Target	Purpose	Important Fields	Field Descriptions
ParticipantRegister	Participant	CLAMP Runtime	Participant registers with the CLAMP runtime	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
ParticipantRegisterAck	CLAMP Runtime	Participant	Acknowledgement of Participant Registration	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				Result	Success/Fail
				Message	Message indicating reason for failure
ParticipantUpdate	CLAMP Runtime	Participant	CLAMP Runtime sends Control Loop Element Definitions and Common Parameter Values to Participants	ParticipantDefinitionUpdateMap	Map with Participant ID as its key, each value on the map is a ControlLoopElementDefintionMap
				ControlLoopElementDefintionMap	List of ControlLoopElementDefinition values for a particular participant, keyed by its Control Loop Element Definition ID
				ControlLoopElementDefinition	A ControlLoopElementToscaServiceTemplate containing the definition of the Control Loop Element and a CommonPropertiesMap with the values of the common property values for Control Loop Elements of this type
				ControlLoopElementToscaServiceTemplate	The definition of the Control Loop Element in TOSCA
				CommonPropertiesMap	A <String, String> map indexed by the property name. Each map entry is the serialized value of the property, which can be deserialized into an instance of the type of the property.
ParticipantUpdateAck	Participant	CLAMP Runtime	Acknowledgement of Participant Update	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				Result	Success/Fail
				Message	Message indicating reason for failure
ParticipantDeregister	Participant	CLAMP Runtime	Participant deregisters with the CLAMP runtime	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
ParticipantDeregisterAck	CLAMP Runtime	Participant	Acknowledgement of Participant Deegistration	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				Result	Success/Fail
				Message	Message indicating reason for failure
ControlLoopUpdate	CLAMP Runtime	Participant	CLAMP Runtime sends Control Loop Element instances and Instance Specific Parameter Values for a Control Loop Instance to Participants	ControlLoopId	The name and version of the Control Loop
				ParticipantUpdateMap	Map with Participant ID as its key, each value on the map is a ControlLoopElementList
				ControlLoopElementList	List of ControlLoopElement values for the Control Loop
				ControlLoopElement	A ControlLoopElement, which contains among other things a PropertiesMap with the values of the property values for this Control Loop Element instance and a ToscaServiceTemplateFragment with extra concept definitions and instances that a participant may need.
				PropertiesMap	A <String, String> map indexed by the property name. Each map entry is the serialized value of the property, which can be deserialized into an instance of the type of the property.
				ToscaServiceTemplateFragment	A well-formed TOSCA service template containing extra concept definitions and instances that a participant may need. For example, the Policy Participant may need policy type definitions or policy instances to be provided if they are not already stored in the Policy Framework.
ControlLoopUpdateAck	Participant	CLAMP Runtime	Acknowledgement of Control Loop Update	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				ControlLoopId	The name and version of the Control Loop
				ControlLoopResult	Holds a Result and Message for the overall operation on the participant and a map of Result and Message fields for each Control Loop Element of the control loop on this participant
				Result	Success/Fail
				Message	Message indicating reason for failure
ControlLoopStateChange	CLAMP Runtime	Participant	CLAMP Runtime asks Participants to change the state of a Control Loop	ControlLoopId	The name and version of the Control Loop
				currentState	The current state of the Control Loop
				orderedState	The state that the Control Loop should transition to
				startPhase	The start phase to which this ControLoopStateChange message applies
ControlLoopStateChangeAck	Participant	CLAMP Runtime	Acknowledgement of Control Loop State Change	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				ControlLoopId	The name and version of the Control Loop
				startPhase	The start phase to which this ControLoopStateChangeAck message applies
				ControlLoopResult	Holds a Result and Message for the overall operation on the participant and a map of Result and Message fields for each Control Loop Element of the control loop on this participant
				Result	Success/Fail
				Message	Message indicating reason for failure
ParticipantStatusReq	CLAMP Runtime	Participant	Request that the specified participants return a ParticipantStatus message immediately	ParticipantId	The ID of this participant, if not specified, all participants respond.
ParticipantStatus	Participant	CLAMP Runtime	Periodic or on-demand report for heartbeat, Participant Status, Control Loop Status, and Control Loop Statistics	ParticipantId	The ID of this participant
				ParticipantType	The type of the participant, maps to the capabilities of the participant in Control Loop Type Definitions
				ParticipantDefinitionUpdateMap (returned in repsonse to ParticipantStatusReq only)	See ParticipantUpdate message above for definition of this field
				ParticipantStatus	The current status of the participant for monitoring
				ParticipantStatistics	Statistics on the participant such as up time, or messages processed. Can include participant specific data in a string blob that is opaque to CLAMP
				ControlLoopInfoMap	A map of ControlLoopInfo types indexed by ControlLoopId, one entry for each control loop running on the participant
				ControlLoopInfo	The ControlLoopStatus and ControlLoopStatistics for a given control loop
				ControlLoopStatus	The current status of the control loop for monitoring
				ControlLoopStatistics	Statistics on the control loop such as up time, or messages processed. Can include participant specific data in a string blob that is opaque to CLAMP

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