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diff --git a/docs/clamp/acm/controlloop-architecture.rst b/docs/clamp/acm/controlloop-architecture.rst new file mode 100644 index 00000000..1c09bea0 --- /dev/null +++ b/docs/clamp/acm/controlloop-architecture.rst @@ -0,0 +1,468 @@ +.. This work is licensed under a Creative Commons Attribution 4.0 International License. + +.. _clamp-controlloop_architecture-label: + +TOSCA Defined Control Loops: Architecture and Design +#################################################### + + +.. contents:: + :depth: 4 + +The idea of using control loops to automatically (or autonomously) perform network management +has been the subject of much research in the Network Management research community, see +:download:`this paper <files/ControlLoops.pdf>` for some background. However, it is only with +the advent of ONAP that we have a platform that supports control loops for network management. +Before ONAP, Control Loops have been implemented by hard-coding components together and hard +coding logic into components. ONAP has taken a step forward towards automatic implementation +of Control Loops by allowing parameterization of Control Loops that work on the premise that +the Control Loops use a set of analytic, policy, and control components connected together in +set ways. + +The goal of the work is to extend and enhance the current ONAP Control Loop support to provide +a complete open-source framework for Control Loops. This will enhance the current support to +provide TOSCA based Control Loop definition and development, commissioning and run-time management. +The participants that comprise a Control Loop and the metadata needed to link the participants +together to create a Control Loop are specified in a standardized way using the `OASIS TOSCA +modelling language <http://docs.oasis-open.org/tosca/TOSCA-Simple-Profile-YAML/>`_. The TOSCA +description is then used to commission, instantiate, and manage the Control Loops in the run +time system. + +.. image:: images/01-controlloop-overview.png + +1 Terminology +============= + +This section describes the terminology used in the system. + +1.1 Control Loop Terminology +---------------------------- + +**Control Loop Type:** A definition of a Control Loop in the TOSCA language. This definition describes +a certain type of a control loop. The life cycle of instances of a Control Loop Type are managed +by CLAMP. + +**Control Loop Instance:** An instance of a Control Loop Type. The life cycle of a Control Loop +Instance is managed by CLAMP. A Control Loop Instance is a set of executing elements on which +Life Cycle Management (LCM) is executed collectively. For example, a set of microservices may be +spawned and executed together to deliver a service. This collection of services is a control loop. + +**Control Loop Element Type:** A definition of a Control Loop Element in the TOSCA language. This +definition describes a certain type of Control Loop Element for a control loop in a Control +Loop Type. + +**Control Loop Element Instance:** A single entity executing on a participant, with its Life Cycle +being managed as part of the overall control loop. For example, a single microservice that is +executing as one microservice in a service. + +**CLAMP Control Loop Runtime:** The CLAMP server that holds Control Loop Type definitions and manages +the life cycle of Control Loop Instances and their Control Loop Elements in cooperation with +participants. + + +1.2 Participant Terminology +--------------------------- + +**Participant Type:** Definition of a type of system or framework that can take part in control +loops and a definition of the capabilities of that participant type. A participant advertises +its type to the CLAMP Control Loop Runtime. + +**Participant:** A system or framework that takes part in control loops by executing Control Loop +Elements in cooperation with the CLAMP Control Loop Runtime. A participant chooses to partake +in control loops, to manage Control Loop Elements for CLAMP, and to receive, send and act on +LCM messages for the CLAMP runtime. + +1.3 Terminology for Properties +------------------------------ + +**Common Properties:** Properties that apply to all Control Loop Instances of a certain Control +Loop Type and are specified when a Control Loop Type is commissioned. + +**Instance Specific Properties:** Properties that must be specified for each Control Loop Instance +and are specified when a Control Loop Instance is Initialized. + +1.4 Concepts and their relationships +------------------------------------ + +The UML diagram below shows the concepts described in the terminology sections above and how +they are interrelated. + +.. image:: images/02-controlloop-concepts.png + +The Control Loop Definition concepts describe the types of things that are in the system. These +concepts are defined at design time and are passed to the runtime in a TOSCA document. The +concepts in the Control Loop Runtime are created by the runtime part of the system using the +definitions created at design time. + +.. _controlloop-capabilities: + +2 Capabilities +============== + +We consider the capabilities of Control Loops at Design Time and Run Time. + +At Design Time, three capabilities are supported: + +#. **Control Loop Element Definition Specification.** This capability allows users to define Control + Loop Element Types and the metadata that can be used on and configured on a Control Loop Element + Type. Users also define the Participant Type that will run the Control Loop Element when it is + taking part in in a control loop. The post condition of an execution of this capability is that + metadata for a Control Loop Element Type is defined in the Control Loop Design Time Catalogue. + +#. **Control Loop Element Definition Onboarding.** This capability allows external users and systems + (such as SDC or DCAE-MOD) to define the metadata that can be used on and configured on a Control + Loop Element Type and to define the Participant Type that will run the Control Loop Element when + it is taking part in in a control loop. The post condition of an execution of this capability + is that metadata for a Control Loop Element Type is defined in the Control Loop Design Time + Catalogue. + +#. **Control Loop Type Definition.** This capability allows users and other systems to create Control + Loop Type definitions by specifying a set of Control Loop Element Definitions from those that + are available in the Control Loop Design Time Catalogue. These Control Loop Elements will + work together to form Control Loops. In an execution of this capability, a user specifies the + metadata for the Control Loop and specifies the set of Control Loop Elements and their Participant + Types. The user also selects the correct metadata sets for each participant in the Control Loop + Type and defines the overall Control Loop Type metadata. The user also specifies the Common + Property Types that apply to all instances of a control loop type and the Instance Specific + Property Types that apply to individual instances of a Control Loop Type. The post condition for + an execution of this capability is a Control Loop definition in TOSCA stored in the Control Loop + Design Time Catalogue. + +.. note:: + Once a Control Loop Definition is commissioned to the Control Loop Runtime and has been + stored in the Run Time Inventory, it cannot be further edited unless it is decommissioned. + + +At Run Time, the following participant related capabilities are supported: + +#. **System Pre-Configuration.** This capability allows participants to register and deregister + with CLAMP. Participants explicitly register with CLAMP when they start. Control Loop Priming + is performed on each participant once it registers. The post condition for an execution of this + capability is that a participant becomes available (registration) or is no longer available + (deregistration) for participation in a control loop. + +#. **Control Loop Priming on Participants.** A participant is primed to support a Control Loop Type. + Priming a participant means that the definition of a control loop and the values of Common + Property Types that apply to all instances of a control loop type on a participant are sent + to a participant. The participant can then take whatever actions it need to do to support + the control loop type in question. Control Loop Priming takes place at participant + registration and at Control Loop Commissioning. The post condition for an execution of this + capability is that all participants in this control loop type are commissioned, that is they + are prepared to run instances of their Control Loop Element types. + + +At Run Time, the following Control Loop Life Cycle management capabilities are supported: + +#. **Control Loop Commissioning:** This capability allows version controlled Control Loop Type + definitions to be taken from the Control Loop Design Time Catalogue and be placed in the + Commissioned Control Loop Inventory. It also allows the values of Common Property Types + that apply to all instances of a Control Loop Type to be set. Further, the Control Loop + Type is primed on all concerned participants. The post condition for an execution of this + capability is that the Control Loop Type definition is in the Commissioned Control Loop + Inventory and the Control Loop Type is primed on concerned participants. + +#. **Control Loop Instance Life Cycle Management:** This capability allows a Control Loop + Instance to have its life cycle managed. + + #. **Control Loop Instance Creation:** This capability allows a Control Loop Instance to be + created. The Control Loop Type definition is read from the Commissioned Control Loop + Inventory and values are assigned to the Instance Specific Property Types defined for + instances of the Control Loop Type in the same manner as the existing CLAMP client does. + A Control Loop Instance that has been created but has not yet been instantiated on + participants is in state UNINITIALIZED. In this state, the Instance Specific Property Type + values can be revised and updated as often as the user requires. The post condition for an + execution of this capability is that the Control Loop instance is created in the + Instantiated Control Loop Inventory but has not been instantiated on Participants. + + #. **Control Loop Instance Update on Participants:** Once the user is happy with the property + values, the Control Loop Instance is updated on participants and the Control Loop Elements + for this Control Loop Instance are initialized or updated by participants using the control + loop metadata. The post condition for an execution of this capability is that the Control + Loop instance is updated on Participants. + + #. **Control Loop State Change:** The user can now order the participants to change the state + of the Control Loop Instance. If the Control Loop is set to state RUNNING, each participant + begins accepting and processing control loop events and the Control Loop Instance is set + to state RUNNING in the Instantiated Control Loop inventory. The post condition for an + execution of this capability is that the Control Loop instance state is changed on + participants. + + #. **Control Loop Instance Monitoring:** This capability allows Control Loop Instances to be + monitored. Users can check the status of Participants, Control Loop Instances, and Control + Loop Elements. Participants report their overall status and the status of Control Loop + Elements they are running periodically to CLAMP. Clamp aggregates these status reports + into an aggregated Control Loop Instance status record, which is available for monitoring. + The post condition for an execution of this capability is that Control Loop Instances are + being monitored. + + #. **Control Loop Instance Supervision:** This capability allows Control Loop Instances to be + supervised. The CLAMP runtime expects participants to report on Control Loop Elements + periodically. The CLAMP runtime checks that periodic reports are received and that each + Control Loop Element is in the state it should be in. If reports are missed or if a + Control Loop Element is in an incorrect state, remedial action is taken and notifications + are issued. The post condition for an execution of this capability is that Control Loop + Instances are being supervised by the CLAMP runtime. + + #. **Control Loop Instance Removal from Participants:** A user can order the removal of a Control + Loop Instance from participants. The post condition for an execution of this capability is + that the Control Loop instance is removed from Participants. + + #. **Control Loop Instance Deletion:** A user can order the removal of a Control Loop Instance + from the CLAMP runtime. Control Loop Instances that are instantiated on participants cannot + be removed from the CLAMP runtime. The post condition for an execution of this capability + is that the Control Loop instance is removed from Instantiated Control Loop Inventory. + +#. **Control Loop Decommissioning:** This capability allows version controlled Control Loop Type + definitions to be removed from the Commissioned Control Loop Inventory. A Control Loop + Definition that has instances in the Instantiated Control Loop Inventory cannot be removed. + The post condition for an execution of this capability is that the Control Loop Type + definition removed from the Commissioned Control Loop Inventory. + +.. note:: + The system dialogues for run time capabilities are described in detail on the + :ref:`System Level Dialogues <system-level-label>` page. + +.. _controlloop-instance-states: + +2.1 Control Loop Instance States +-------------------------------- + +When a control loop definition has been commissioned, instances of the control loop can be +created, updated, and deleted. The system manages the lifecycle of control loops and control +loop elements following the state transition diagram below. + +.. image:: images/03-controlloop-instance-states.png + +3 Overall Target Architecture +============================= + +The diagram below shows an overview of the architecture of TOSCA based Control Loop +Management in CLAMP. + +.. image:: images/04-overview.png + +Following the ONAP Reference Architecture, the architecture has a Design Time part and +a Runtime part. + +The Design Time part of the architecture allows a user to specify metadata for participants. +It also allows users to compose control loops. The Design Time Catalogue contains the metadata +primitives and control loop definition primitives for composition of control loops. As shown +in the figure above, the Design Time component provides a system where Control Loops can be +designed and defined in metadata. This means that a Control Loop can have any arbitrary +structure and the Control Loop developers can use whatever analytic, policy, or control +participants they like to implement their Control Loop. At composition time, the user +parameterises the Control Loop and stores it in the design time catalogue. This catalogue +contains the primitive metadata for any participants that can be used to compose a Control +Loop. A Control Loop SDK is used to compose a Control Loop by aggregating the metadata for +the participants chosen to be used in a Control Loop and by constructing the references between +the participants. The architecture of the Control Loop Design Time part will be elaborated in +future releases. + +Composed Control Loops are commissioned on the run time part of the system, where they are +stored in the Commissioned Control Loop inventory and are available for instantiation. The +Commissioning component provides a CRUD REST interface for Control Loop Types, and implements +CRUD of Control Loop Types. Commissioning also implements validation and persistence of incoming +Control Loop Types. It also guarantees the integrity of updates and deletions of Control Loop +Types, such as performing updates in accordance with semantic versioning rules and ensuring that +deletions are not allowed on Control Loop Types that have instances defined. + +The Instantiation component manages the Life Cycle Management of Control Loop Instances and +their Control Loop Elements. It publishes a REST interface that is used to create Control Loop +Instances and set values for Common and Instance Specific properties. This REST interface is +public and is used by the CLAMP GUI. It may also be used by any other client via the public +REST interface. the REST interface also allows the state of Control Loop Instances to be changed. +A user can change the state of Control Loop Instances as described in the state transition +diagram shown in section 2 above. The Instantiation component issues update and state change +messages via DMaaP to participants so that they can update and manage the state of the Control +Loop Elements they are responsible for. The Instantiation component also implements persistence +of Control Loop Instances, control loop elements, and their state changes. + +The Monitoring component reads updates sent by participants. Participants report on the +state of their Control Loop Elements periodically and in response to a message they have +received from the Instantiation component. The Monitoring component reads the contents of +the participant messages and persists their state updates and statistics records. It also +publishes a REST interface that publishes the current state of all Participants, Control +Loop Instances and their Control Loop Elements, as well as publishing Participant and +Control Loop statistics. + +The Supervision component is responsible for checking that Control Loop Instances are correctly +instantiated and are in the correct state (UNINITIALIZED/READY/RUNNING). It also handles +timeouts and on state changes to Control Loop Instances, and retries and rolls back state +changes where state changes failed. + +A Participant is an executing component that partakes in control loops. More explicitly, a +Participant is something that implements the Participant Instantiation and Participant +Monitoring messaging protocol over DMaaP for Life Cycle management of Control Loop Elements. +A Participant runs Control Loop Elements and manages and reports on their life cycle +following the instructions it gets from the CLAMP runtime in messages delivered over DMaaP. + +In the figure above, five participants are shown. A Configuration Persistence Participant +manages Control Loop Elements that interact with the `ONAP Configuration Persistence Service +<https://docs.onap.org/projects/onap-cps/en/latest/overview.html>`_ +to store common data. The DCAE Participant runs Control Loop Elements that manage DCAE +microservices. The Kubernetes Participant hosts the Control Loop Elements that are managing +the life cycle of microservices in control loops that are in a Kubernetes ecosystem. The +Policy Participant handles the Control Loop Elements that interact with the Policy Framework +to manage policies for control loops. A Controller Participant such as the CDS Participant +runs Control Loop Elements that load metadata and configure controllers so that they can +partake in control loops. Any third party Existing System Participant can be developed to +run Control Loop Elements that interact with any existing system (such as an operator's +analytic, machine learning, or artificial intelligence system) so that those systems can +partake in control loops. + +4. Other Considerations +======================= + +.. _management-cl-instance-configs: + +4.1 Management of Control Loop Instance Configurations +------------------------------------------------------ + +In order to keep management of versions of the configuration of control loop instances +straightforward and easy to implement, the following version management scheme using +semantic versioning is implemented. Each configuration of a Control Loop Instance and +configuration of a Control Loop Element has a semantic version with 3 digits indicating +the **major.minor.patch** number of the version. + +.. note:: + A **configuration** means a full set of parameter values for a Control Loop Instance. + +.. image:: images/05-upgrade-states.png + +Change constraints: + +#. A Control Loop or Control Loop Element in state **RUNNING** can be changed to a higher patch + level or rolled back to a lower patch level. This means that hot changes that do not + impact the structure of a Control Loop or its elements can be executed. + +#. A Control Loop or Control Loop Element in state **PASSIVE** can be changed to a higher + minor/patch level or rolled back to a lower minor/patch level. This means that structural + changes to Control Loop Elements that do not impact the Control Loop as a whole can be + executed by taking the control loop to state **PASSIVE**. + +#. A Control Loop or Control Loop Element in state **UNINITIALIZED** can be changed to a higher + major/minor/patch level or rolled back to a lower major/minor/patch level. This means + that where the structure of the entire control loop is changed, the control loop must + be uninitialized and reinitialized. + +#. If a Control Loop Element has a **minor** version change, then its Control Loop Instance + must have at least a **minor** version change. + +#. If a Control Loop Element has a **major** version change, then its Control Loop Instance + must have a **major** version change. + +4.2 Scalability +--------------- + +The system is designed to be inherently scalable. The CLAMP runtime is stateless, all state +is preserved in the Instantiated Control Loop inventory in the database. When the user +requests an operation such as an instantiation, activation, passivation, or an uninitialization +on a Control Loop Instance, the CLAMP runtime broadcasts the request to participants over +DMaaP and saves details of the request to the database. The CLAMP runtime does not directly +wait for responses to requests. + +When a request is broadcast on DMaaP, the request is asynchronously picked up by participants +of the types required for the Control Loop Instance and those participants manage the life +cycle of its control loop elements. Periodically, each participant reports back on the status +of operations it has picked up for the Control Loop Elements it controls, together with +statistics on the Control Loop Elements over DMaaP. On reception of these participant messages, +the CLAMP runtime stores this information to its database. + +The participant to use on a control loop can be selected from the registered participants +in either of two ways: + +**Runtime-side Selection:** The CLAMP runtime selects a suitable participant from the list of +participants and sends the participant ID that should be used in the Participant Update message. +In this case, the CLAMP runtime decides on which participant will run the Control Loop Element +based on a suitable algorithm. Algorithms could be round robin based or load based. + +**Participant-side Selection:** The CLAMP runtime sends a list of Participant IDs that may be used +in the Participant Update message. In this case, the candidate participants decide among +themselves which participant should host the Control Loop Element. + +This approach makes it easy to scale Control Loop life cycle management. As Control Loop +Instance counts increase, more than one CLAMP runtime can be deployed and REST/supervision +operations on Control Loop Instances can run in parallel. The number of participants can +scale because an asynchronous broadcast mechanism is used for runtime-participant communication +and there is no direct connection or communication channel between participants and CLAMP +runtime servers. Participant state, Control Loop Instance state, and Control Loop Element +state is held in the database, so any CLAMP runtime server can handle operations for any +participant. Because many participants of a particular type can be deployed and participant +instances can load balance control loop element instances for different Control Loop Instances +of many types across themselves using a mechanism such as a Kubernetes cluster. + + +4.3 Sandboxing and API Gateway Support +-------------------------------------- + +At runtime, interaction between ONAP platform services and application microservices are +relatively unconstrained, so interactions between Control Loop Elements for a given Control +Loop Instance remain relatively unconstrained. A +`proposal to support access-controlled access to and between ONAP services +<https://wiki.onap.org/pages/viewpage.action?pageId=103417456>`_ +will improve this. This can be complemented by intercepting and controlling services +accesses between Control Loop Elements for Control Loop Instances for some/all Control +Loop types. + +API gateways such as `Kong <https://konghq.com/kong/>`_ have emerged as a useful technology +for exposing and controlling service endpoint access for applications and services. When a +Control Loop Type is onboarded, or when Control Loop Instances are created in the Participants, +CLAMP can configure service endpoints between Control Loop Elements to redirect through an +API Gateway. + +Authentication and access-control rules can then be dynamically configured at the API gateway +to support constrained access between Control Loop Elements and Control Loop Instances. + +The diagram below shows the approach for configuring API Gateway access at Control Loop +Instance and Control Loop Element level. + +.. image:: images/06-api-gateway-sandbox.png + +At design time, the Control Loop type definition specifies the type of API gateway configuration +that should be supported at Control Loop and Control Loop Element levels. + +At runtime, the CLAMP can configure the API gateway to enable (or deny) interactions between +Control Loop Instances and individually for each Control Loop Element. All service-level +interactions in/out of a Control Loop Element, except that to/from the API Gateway, can be +blocked by networking policies, thus sandboxing a Control Loop Element and an entire Control +Loop Instance if desired. Therefore, a Control Loop Element will only have access to the APIs +that are configured and enabled for the Control Loop Element/Instance in the API gateway. + +For some Control Loop Element Types the Participant can assist with service endpoint +reconfiguration, service request/response redirection to/from the API Gateway, or +annotation of requests/responses. + +Once the Control Loop instance is instantiated on participants, the participants configure +the API gateway with the Control Loop Instance level configuration and with the specific +configuration for their Control Loop Element. + +Monitoring and logging of the use of the API gateway may also be provided. Information and +statistics on API gateway use can be read from the API gateway and passed back in monitoring +messages to the CLAMP runtime. + +Additional isolation and execution-environment sandboxing can be supported depending on the +Control Loop Element Type. For example: ONAP policies for given Control Loop Instances/Types +can be executed in a dedicated PDP engine instances; DCAE or K8S-hosted services can executed +in isolated namespaces or in dedicated workers/clusters; etc.. + + +5 APIs and Protocols +==================== + +The APIs and Protocols used by CLAMP for Control Loops are described on the pages below: + +#. :ref:`System Level Dialogues <system-level-label>` +#. :ref:`The CLAMP Control Loop Participant Protocol <controlloop-participant-protocol-label>` +#. :ref:`REST APIs for CLAMP Control Loops <controlloop-rest-apis-label>` + + +6 Design and Implementation +=========================== + +The design and implementation of TOSCA Control Loops in CLAMP is described for each executable entity on the pages below: + +#. :ref:`The CLAMP Control Loop Runtime Server <clamp-runtime-acm>` +#. :ref:`CLAMP Control Loop Participants <clamp-controlloop-participants>` +#. :ref:`Managing Control Loops using The CLAMP GUI <clamp-gui-controlloop>` + +End of Document |