1 .. This work is licensed under a
2 .. Creative Commons Attribution 4.0 International License.
3 .. http://creativecommons.org/licenses/by/4.0
6 .. _architecture-label:
8 Policy Framework Architecture
9 #############################
13 This document describes the ONAP Policy Framework. It lays out the architecture of the framework and shows the APIs
14 provided to other components that interwork with the framework. It describes the implementation of the framework,
15 mapping out the components, software structure, and execution ecosystem of the framework.
23 The ONAP Policy Framework is a comprehensive policy design, deployment, and execution environment. The Policy Framework
24 is the decision making component in `an ONAP system
25 <https://www.onap.org/wp-content/uploads/sites/20/2018/11/ONAP_CaseSolution_Architecture_112918FNL.pdf>`__.
26 It allows you to specify, deploy, and execute the governance of the features and functions in your ONAP system, be they
27 closed loop, orchestration, or more traditional open loop use case implementations. The Policy Framework is the
28 component that is the source of truth for all policy decisions.
30 One of the most important goals of the Policy Framework is to support Policy Driven Operational Management during the
31 execution of ONAP control loops at run time. In addition, use case implementations such as orchestration and control
32 benefit from the ONAP policy Framework because they can use the capabilities of the framework to manage and execute
33 their policies rather than embedding the decision making in their applications.
35 The Policy Framework is deployment agnostic, it manages Policy Execution (in PDPs) and Enforcement (in PEPs) regardless
36 of how the PDPs and PEPs are deployed. This allows policy execution and enforcement to be deployed in a manner that
37 meets the performance requirements of a given application or use case. In one deployment, policy execution could be
38 deployed in a separate executing entity in a Docker container. In another, policy execution could be co-deployed with
39 an application to increase performance. An example of co-deployment is the Drools PDP Control Loop image, which is a
40 Docker image that combines the ONAP Drools use case application and dependencies with the Drools PDP engine.
42 The ONAP Policy Framework architecture separates policies from the platform that is supporting them. The framework
43 supports development, deployment, and execution of any type of policy in ONAP. The Policy Framework is metadata (model)
44 driven so that policy development, deployment, and execution is as flexible as possible and can support modern rapid
45 development ways of working such as `DevOps
46 <https://en.wikipedia.org/wiki/DevOps>`__. A metadata driven approach also allows the amount of programmed support
47 required for policies to be reduced or ideally eliminated.
49 We have identified five capabilities as being essential for the framework:
51 1. Most obviously, the framework must be capable of being triggered by an event or invoked, and making decisions at run
54 2. It must be deployment agnostic; capable of managing policies for various Policy Decision Points (PDPs) or policy
57 3. It must be metadata driven, allowing policies to be deployed, modified, upgraded, and removed as the system executes.
59 4. It must provide a flexible model driven policy design approach for policy type programming and specification of
62 5. It must be extensible, allowing straightforward integration of new PDPs, policy formats, and policy development
65 Another important aim of the architecture of a model driven policy framework is that it enables much more flexible
66 policy specification. The ONAP Policy Framework complies with the `TOSCA
67 <http://docs.oasis-open.org/tosca/TOSCA-Simple-Profile-YAML/v1.1/TOSCA-Simple-Profile-YAML-v1.1.pdf>`__ modelling
68 approach for policies, see the :ref:`TOSCA Policy Primer <tosca-label>` for more information on how policies are modeled
71 1. A *Policy Type* describes the properties, targets, and triggers that the policy for a feature can have. A Policy type is
72 implementation independent. It is the metadata that specifies:
74 - the *configuration* data that the policy can take. The Policy Type describes each property that a policy of a
75 given type can take. A Policy Type definition also allows the default value, optionality, and the ranges of properties
78 - the *targets* such as network element types, functions, services, or resources on which a policy of the given type
81 - the *triggers* such as the event type, filtered event, scheduled trigger, or conditions that can activate a policy
84 Policy Types are hierarchical, A Policy Type can inherit from a parent Policy Type, inheriting the properties, targets,
85 and triggers of its parent. Policy Types are developed by domain experts in consultation with the developers that
86 implement the logic and rules for the Policy Type.
88 2. A *Policy* is defined using a Policy Type. The Policy defines:
90 - the values for each property of the policy type
91 - the specific targets (network elements, functions, services, resources) on which this policy will act
92 - the specific triggers that trigger this policy.
94 3. A *Policy Type Implementation* or *Raw Policy*, is the logic that implements the policy. It is implemented by a
95 skilled policy developer in consultation with domain experts. The implementation has software that reads the Policy
96 Type and parses the incoming configuration properties. The software has domain logic that is triggered when one of the
97 triggers described in the Policy Type occurs. The software logic executes and acts on the targets specified in the
101 For example, a Policy Type could be written to describe how to manage Service Level Agreements for VPNs. The VPN Policy
102 Type can be used to create VPN policies for a bank network, a car dealership network, or a university with many campuses.
103 The Policy Type has two parameters:
105 - The *maximumDowntime* parameter allows the maximum downtime allowed per year to be specified
106 - The *mitigationStrategy* parameter allows one of three strategies to be selected for downtime breaches
108 - *allocateMoreResources*, which will automatically allocate more resources to mitigate the problem
109 - *report*, which report the downtime breach to a trouble ticketing system
110 - *ignore*, which logs the breach and takes no further action
112 The Policy Type defines a trigger event, an event that is received from an analytics system when the maximum downtime
113 value for a VPN is breached. The target of the policy type is an instance of the VPN service.
115 The Policy Type Implementation is developed that can configure the maximum downtime parameter in an analytics system,
116 can receive a trigger from the analytics system when the maximum downtime is breached, and that can either request more
117 resources, report an issue to a trouble ticketing system, and can log a breach.
119 VPN Policies are created by specifying values for the properties, triggers, and targets specified in VPN Policy Type.
121 In the case of the bank network, the *maximumDowntime* threshold is specified as 5 minutes downtime per year and the
122 *mitigationStrategy* is defined as *allocateMoreResources*, and the target is specified as being the bank's VPN service
123 ID. When a breach is detected by the analytics system, the policy is executed, the target is identified as being the
124 bank's network, and more resources are allocated by the policy.
126 For the car dealership VPN policy, a less stringent downtime threshold of 60 minutes per year is specified, and the
127 mitigation strategy is to issue a trouble ticket. The university network is best effort, so a downtime of 4 days per
128 year is specified. Breaches are logged and mitigated as routine network administration tasks.
130 In ONAP, specific ONAP Policy Types are used to create specific policies that drive the ONAP Platform and Components.
131 For more detailed information on designing Policy Types and developing an implementation for that policy type, see
132 :ref:`Policy Design and Development <design-label>`.
134 The ONAP Policy Framework for building, configuring and deploying PDPs is extendable. It allows the use of ONAP PDPs as
135 is, the extension of ONAP PDPs, and lastly provides the capability for users to create and deploy their own PDPs. The
136 ONAP Policy Framework provides distributed policy management for **all** policies in ONAP at run time. Not only does
137 this provide unified policy access and version control, it provides life cycle control for policies and allows detection
138 of conflicts across all policies running in an ONAP installation.
143 The diagram below shows the architecture of the ONAP Policy Framework at its highest level.
145 .. image:: images/PFHighestLevel.svg
147 The *PolicyDevelopment* component implements the functionality for development of policy types and policies.
148 *PolicyAdministration* is responsible for the deployment life cycle of policies as well as interworking with the
149 mechanisms required to orchestrate the nodes and containers on which policies run. *PolicyAdministration* is also
150 responsible for the administration of policies at run time; ensuring that policies are available to users, that policies
151 are executing correctly, and that the state and status of policies is monitored. *PolicyExecution* is the set of PDPs
152 running in the ONAP system and is responsible for making policy decisions and for managing the administrative state of
153 the PDPs as directed by \ *PolicyAdministration.*
155 *PolicyDevelopment* provides APIs that allow creation of policy artifacts and supporting information in the policy
156 database. *PolicyAdministration* reads those artifacts and the supporting information from the policy database whilst
157 deploying policy artifacts. Once the policy artifacts are deployed, *PolicyAdministration* handles the run-time
158 management of the PDPs on which the policies are running. *PolicyDevelopment* interacts with the database, and has
159 no programmatic interface with *PolicyAdministration*, *PolicyExecution* or any other run-time ONAP components.
161 The diagram below shows a more detailed view of the architecture, as inspired by
162 `RFC-2753 <https://tools.ietf.org/html/rfc2753>`__ and `RFC-3198 <https://tools.ietf.org/html/rfc3198>`__.
164 .. image:: images/PFDesignAndAdmin.svg
166 *PolicyDevelopment* provides a `CRUD <https://en.wikipedia.org/wiki/Create,_read,_update_and_delete>`__ API for policy
167 types and policies. The policy types and policy artifacts and their metadata (information about policies, policy types,
168 and their interrelations) are stored in the *PolicyDB*. The *PolicyDevGUI*, PolicyDistribution, and other applications
169 such as *CLAMP* can use the *PolicyDevelopment* API to create, update, delete, and read policy types and policies.
171 *PolicyAdministration* has two important functions:
173 - Management of the life cycle of PDPs in an ONAP installation. PDPs register with *PolicyAdministration* when they come
174 up. *PolicyAdministration* handles the allocation of PDPs to PDP Groups and PDP Subgroups, so that they can be
175 managed as microservices in infrastructure management systems such as Kubernetes.
177 - Management of the deployment of policies to PDPs in an ONAP installation. *PolicyAdministration* gives each PDP group
178 a set of domain policies to execute.
180 *PolicyAdministration* handles PDPs and policy allocation to PDPs using asynchronous messaging over DMaaP. It provides
183 - a CRUD API for policy groups and subgroups
185 - an API that allows the allocation of policies to PDP groups and subgroups to be controlled
187 - an API allows policy execution to be managed, showing the status of policy execution on PDP Groups, subgroups, and
188 individual PDPs as well as the life cycle state of PDPs
190 *PolicyExecution* is the set of running PDPs that are executing policies, logically partitioned into PDP groups and
193 .. image:: images/PolicyExecution.svg
195 The figure above shows how *PolicyExecution* looks at run time with PDPs running in Kubernetes. A *PDPGroup* is a purely
196 logical construct that collects all the PDPs that are running policies for a particular domain together. A *PDPSubGroup*
197 is a group of PDPs of the same type that are running the same policies. *A PDPSubGroup* is deployed as a Kubernetes
198 `Deployment <https://kubernetes.io/docs/concepts/workloads/controllers/deployment/>`__. PDPs are defined as Kubernetes
199 `Pods <https://kubernetes.io/docs/concepts/workloads/pods/pod/>`__. At run time, the actual number of PDPs in each
200 *PDPSubGroup* is specified in the configuration of the *Deployment* of that *PDPSubGroup* in Kubernetes. This
201 structuring of PDPs is required because, in order to simplify deployment and scaling of PDPs in Kubernetes, we gather
202 all the PDPs of the same type that are running the same policies together for deployment.
204 For example, assume we have policies for the SON (Self Organizing Network) and ACPS (Advanced Customer Premises Service)
205 domains. For SON,we have XACML, Drools, and APEX policies, and for ACPS we have XACML and Drools policies. The table
206 below shows the resulting \ *PDPGroup*, *PDPSubGroup*, and PDP allocations:
208 ============= ================ ========================= ======================================== ================
209 **PDP Group** **PDP Subgroup** **Kubernetes Deployment** **Kubernetes Deployment Strategy** **PDPs in Pods**
210 ============= ================ ========================= ======================================== ================
211 SON SON-XACML SON-XACML-Dep Always 2, be geo redundant 2 PDP-X
212 \ SON-Drools SON-Drools-Dep At Least 4, scale up on 70% load, >= 4 PDP-D
213 scale down on 40% load, be geo-redundant
214 \ SON-APEX SON-APEX-Dep At Least 3, scale up on 70% load, scale >= 3 PDP-A
215 down on 40% load, be geo-redundant
216 ACPS ACPS-XACML ACPS-XACML-Dep Always 2 2 PDP-X
217 \ ACPS-Drools ACPS-Drools-Dep At Least 2, scale up on 80% load, scale >=2 PDP-D
219 ============= ================ ========================= ======================================== ================
221 For more details on *PolicyAdministration* APIs and management of *PDPGroup* and *PDPSubGroup*, see the documentation
222 for :ref:`Policy Administration Point (PAP) Architecture <pap-label>`.
224 2.1 Policy Framework Object Model
225 ---------------------------------
227 This section describes the structure of and relations between the main concepts in the Policy Framework. This model is
228 implemented as a common model and is used by *PolicyDevelopment*, *PolicyDeployment,* and *PolicyExecution.*
230 .. image:: images/ClassStructure.svg
232 The UML class diagram above shows thePolicy Framework Object Model.
234 2.2 Policy Design Architecture
235 ------------------------------
237 This section describes the architecture of the model driven system used to develop policy types and to create
238 policies using policy types. The output of Policy Design is deployment-ready artifacts and Policy metadata in the Policy
241 Policy types that are expressed via natural language or a model require an implementation that allows them to be
242 translated into runtime policies. Some Policy Type implementations are set up and available in the platform during
243 startup such as Control Loop Operational Policy Models, OOF placement Models, DCAE microservice models. Policy type
244 implementations can also be loaded and deployed at run time.
246 2.2.1 Policy Type Design
247 ^^^^^^^^^^^^^^^^^^^^^^^^
249 Policy Type Design is the task of creating policy types that capture the generic and vendor independent aspects of a
250 policy for a particular domain use case.
252 All policy types are specified in TOSCA service templates. Once policy types are defined and created in the system,
253 *PolicyDevelopment* manages them and uses them to allow policies to be created from these policy types in a uniform
254 way regardless of the domain that the policy type is addressing or the PDP technology that will execute the policy.
256 A *PolicyTypeImpl* is developed for a policy type for a certain type of PDP (for example XACML oriented for decision
257 policies, Drools rules or Apex state machines oriented for ECA policies). While a policy type is implementation
258 independent, a policy type implementation for a policy type is specific for the technology of the PDP on which
259 policies that use that policy type implementation will execute. A Policy Type may have many implementations. A
260 *PolicyTypeImpl* is the specification of the specific rules or tasks, the flow of the policy, its internal states
261 and data structures and other relevant information. A *PolicyTypeImpl* can be specific to a particular policy type
262 or it can be more general, providing the implementation of a class of policy types. Further, the design environment
263 and tool chain for implementing implementations of policy types is specific to the technology of the PDP on which
264 the implementation will run.
266 In the *xacml-pdp* and *drools-pdp*, an *application* is written for a given category of policy types. Such an
267 application may have logic written in Java or another programming language, and may have additional artifacts such
268 as scripts and SQL queries. The *application* unmarshals and marshals events going into and out of policies as well
269 as handling the sequencing of events for interactions of the policies with other components in ONAP. For example,
270 *drools-applications* handles the interactions for operational policies running in the drools PDP. In the
271 *apex-pdp*, all unmarshaling, marshaling, and component interactions are captured in the state machine, logic, and
272 configuraiton of the policy, a Java application is not used.
274 *PolicyDevelopment* provides the RESTful :ref:`Policy Design API <design-label>`, which allows other components to query
275 policy types, Those components can then create policies that specify values for the properties, triggers, and targets
276 specified in a policy type. This API is used by components such as *CLAMP* and *PolicyDistribution* to create policies
279 Consider a policy type created for managing faults on vCPE equipment in a vendor independent way. The policy type
280 implementation captures the generic logic required to manage the faults and specifies the vendor specific information
281 that must be supplied to the type for specific vendor vCPE VFs. The actual vCPE policy that is used for managing
282 particular vCPE equipment is created by setting the properties specified in the policy type for that vendor model
285 2.2.1.1 Generating Policy Types
286 """""""""""""""""""""""""""""""
288 It is possible to generate policy types using MDD (Model Driven Development) techniques. Policy types are expressed
289 using a DSL (Domain Specific Language) or a policy specification environment for a particular application domain. For
290 example, policy types for specifying SLAs could be expressed in a SLA DSL and policy types for managing SON features
291 could be generated from a visual SON management tool. The ONAP Policy framework provides an API that allows tool chains
292 to create policy types, see the :ref:`Policy Design and Development <design-label>` page.
294 .. image:: images/PolicyTypeDesign.svg
296 A GUI implementation in another ONAP component (a *PolicyTypeDesignClient*) may use the *API_User* API to create and
297 edit ONAP policy types.
299 2.2.1.2 Programming Policy Type Implementations
300 """""""""""""""""""""""""""""""""""""""""""""""
302 For skilled developers, the most straightforward way to create a policy type is to program it. Programming a policy type
303 might simply mean creating and editing text files, thus manually creating the TOSCA Policy Type YAML file and the policy
304 type implementation for the policy type.
306 A more formal approach is preferred. For policy type implementations, programmers use a specific Eclipse project type
307 for developing each type of implementation, a Policy Type Implementation SDK. The project is under source control in
308 git. This Eclipse project is structured correctly for creating implementations for a specific type of PDP. It includes
309 the correct POM files for generating the policy type implementation and has editors and perspectives that aid
310 programmers in their work
315 The *PolicyCreation* function of *PolicyDevelopment* creates policies from a policy type. The information expressed
316 during policy type design is used to parameterize a policy type to create an executable policy. A service designer
317 and/or operations team can use tooling that reads the TOSCA Policy Type specifications to express and capture a policy
318 at its highest abstraction level. Alternatively, the parameter for the policy can be expressed in a raw JSON or YAML
319 file and posted over the policy design API described on the :ref:`Policy Design and Development <design-label>` page.
321 A number of mechanisms for policy creation are supported in ONAP. The process in *PolicyDevelopment* for creating a
322 policy is the same for all mechanisms. The most general mechanism for creating a policy is using the RESTful
323 *Policy Design API*, which provides a full interface to the policy creation support of *PolicyDevelopment*. This API may
324 be exercised directly using utilities such as *curl*.
326 In future releases, the Policy Framework may provide a command line tool that will be a loose wrapper around the API. It
327 may also provide a general purpose Policy GUI in the ONAP Portal for policy creation, which again would be a general
328 purpose wrapper around the policy creation API. The Policy GUI would interpret any TOSCA Model that has been loaded into
329 it and flexibly presents a GUI for a user to create policies from. The development of these mechanisms will be phased
330 over a number of ONAP releases.
332 A number of ONAP components use policy in manners which are specific to their particular needs. The manner in which the
333 policy creation process is triggered and the way in which information required to create a policy is specified and
334 accessed is specialized for these ONAP components.
336 For example, *CLAMP* provides a GUI for creation of Control Loop policies, which reads the Policy Type associated
337 with a control loop, presents the properties as fields in its GUI, and creates a policy using the property values entered
340 The following subsections outline the mechanisms for policy creation and modification supported by the ONAP Policy
343 2.2.2.1 Policy Design in the ONAP Policy Framework
344 """"""""""""""""""""""""""""""""""""""""""""""""""
346 Policy creation in *PolicyDevelopment* follows the general sequence shown in the sequence diagram below. An *API_USER*
347 is any component that wants to create a policy from a policy type. *PolicyDevelopment* supplies a REST interface that
348 exposes the API and also provides a command line tool and general purpose client that wraps the API.
350 .. image:: images/PolicyDesign.svg
352 An *API_User* first gets a reference to and the metadata for the Policy type for the policy they want to work on from
353 *PolicyDevelopment*. *PolicyDevelopment* reads the metadata and artifact for the policy type from the database. The
354 *API_User* then asks for a reference and the metadata for the policy. *PolicyDevelopment* looks up the policy in the
355 database. If the policy already exists, *PolicyDevelopment* reads the artifact and returns the reference of the existing
356 policy to the *API_User* with the metadata for the existing policy. If the policy does not exist, *PolicyDevelopment*
357 informs the *API_User*.
359 The *API_User* may now proceed with a policy specification session, where the parameters are set for the policy using
360 the policy type specification. Once the *API_User* is happy that the policy is completely and correctly specified, it
361 requests *PolicyDevelopment* to create the policy. *PolicyDevelopment* creates the policy, stores the created policy
362 artifact and its metadata in the database.
364 2.2.2.2 Model Driven VF (Virtual Function) Policy Design via VNF SDK Packaging
365 """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
367 VF vendors express policies such as SLA, Licenses, hardware placement, run-time metric suggestions, etc. These details
368 are captured within the VNF SDK and uploaded into the SDC Catalog. The `SDC Distribution APIs
369 <https://wiki.onap.org/display/DW/SDC+Distribution+client+AID>`__ are used to interact with SDC. For example, SLA and
370 placement policies may be captured via TOSCA specification. License policies can be captured via TOSCA or an XACML
371 specification. Run-time metric vendor recommendations can be captured via the VES Standard specification.
373 The sequence diagram below is a high level view of SDC-triggered concrete policy generation for some arbitrary entity
374 *EntityA*. The parameters to create a policy are read from a TOSCA Policy specification read from a CSAR received from
377 .. image:: images/ModelDrivenPolicyDesign.svg
379 *PolicyDesign* uses the *PolicyDistribution* component for managing SDC-triggered policy creation and update requests.
380 *PolicyDistribution* is an *API_User*, it uses the Policy Design API for policy creation and update. It reads the
381 information it needs to populate the policy type from a TOSCA specification in a CSAR received from SDC and then uses
382 this information to automatically generate a policy.
384 Note that SDC provides a wrapper for the SDC API as a Java Client and also provides a TOSCA parser. See the
385 documentation for the `Policy Distribution Component
386 <https://docs.onap.org/en/latest/submodules/policy/distribution.git/docs/index.html>`__.
388 In Step 4 above, the \ *PolicyDesign* must download the CSAR file. If the policy is to be composed from the TOSCA
389 definition, it must also parse the TOSCA definition.
391 In Step 11 above, the \ *PolicyDesign* must send back/publish status events to SDC such as DOWNLOAD_OK, DOWNLOAD_ERROR,
392 DEPLOY_OK, DEPLOY_ERROR, NOTIFIED.
394 2.2.2.3 Scripted Model Driven Policy Design
395 """""""""""""""""""""""""""""""""""""""""""
397 Service policies such as optimization and placement policies can be specified as a TOSCA Policy at design time. These
398 policies use a TOSCA Policy Type specification as their schemas. Therefore, scripts can be used to create TOSCA policies
399 using TOSCA Policy Types.
401 .. image:: images/ScriptedPolicyDesign.svg
403 One straightforward way of generating policies from Policy types is to use commands specified in a script file. A
404 command line utility such as *curl* is an *API_User*. Commands read policy types using the Policy Type API, parse the
405 policy type and uses the properties of the policy type to prepare a TOSCA Policy. It then issues further commands to use
406 the Policy API to create policies.
408 2.2.3 Policy Design Process
409 ^^^^^^^^^^^^^^^^^^^^^^^^^^^
411 All policy types must be certified as being fit for deployment prior to run time deployment. Where design is executed
412 using the SDC application, it is assumed the life cycle being implemented by SDC certifies any policy types that
413 are declared within the ONAP Service CSAR. For other policy types and policy type implementations, the life cycle
414 associated with the applied software development process suffices. Since policy types and their implementations are
415 designed and implemented using software development best practices, they can be utilized and configured for various
416 environments (eg. development, testing, production) as desired.
418 2.3 Policy Runtime Architecture
419 -------------------------------
421 The Policy Framework Platform components are themselves designed as microservices that are easy to configure and deploy
422 via Docker images and K8S both supporting resiliency and scalability if required. PAPs and PDPs are deployed by the
423 underlying ONAP management infrastructure and are designed to comply with the ONAP interfaces for deploying containers.
425 The PAPs keep track of PDPs, support the deployment of PDP groups and the deployment of a *policy set* across those PDP
426 groups. A PAP is stateless in a RESTful sense. Therefore, if there is more than one PAP deployed, it does not matter
427 which PAP a user contacts to handle a request. The PAP uses the database (persistent storage) to keep track of ongoing
428 sessions with PDPs. Policy management on PDPs is the responsibility of PAPs; management of policy sets or policies by
429 any other manner is not permitted.
431 In the ONAP Policy Framework, the interfaces to the PDP are designed to be as streamlined as possible. Because the PDP
432 is the main unit of scalability in the Policy Framework, the framework is designed to allow PDPs in a PDP group to
433 arbitrarily appear and disappear and for policy consistency across all PDPs in a PDP group to be easily maintained.
434 Therefore, PDPs have just two interfaces; an interface that users can use to execute policies and interface to the PAP
435 for administration, life cycle management and monitoring. The PAP is responsible for controlling the state across the
436 PDPs in a PDP group. The PAP interacts with the Policy database and transfers policy sets to PDPs, and may cache the
437 policy sets for PDP groups.
439 See also Section 2 of the :ref:`Policy Design and Development <design-label>` page, where the mechanisms for PDP
440 Deployment and Registration with PAP are explained.
442 2.3.1 Policy Framework Services
443 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
445 The ONAP Policy Framework follows the architectural approach for microservices recommended by the `ONAP Architecture
446 Subcommittee <https://wiki.onap.org/display/DW/Architecture+Subcommittee>`__.
448 The ONAP Policy Framework uses an infrastructure such as Kubernetes `Services
449 <https://kubernetes.io/docs/concepts/services-networking/service/>`__ to manage the life cycle of Policy Framework
450 executable components at runtime. A Kubernetes service allows, among other parameters, the number of instances (*pods*
451 in Kubernetes terminology) that should be deployed for a particular service to be specified and a common endpoint for
452 that service to be defined. Once the service is started in Kubernetes, Kubernetes ensures that the specified number of
453 instances is always kept running. As requests are received on the common endpoint, they are distributed across the
454 service instances. More complex call distribution and instance deployment strategies may be used; please see the
455 `Kubernetes Services <https://kubernetes.io/docs/concepts/services-networking/service/>`__ documentation for those
458 If, for example, a service called *policy-pdpd-control-loop* is defined that runs 5 PDP-D instances. The service has the
459 end point *https://policy-pdpd-control-loop.onap/<service-specific-path>*. When the service is started, Kubernetes spins
460 up 5 PDP-Ds. Calls to the end point *https://policy-pdpd-control-loop.onap/<service-specific-path>* are distributed
461 across the 5 PDP-D instances. Note that the *.onap* part of the service endpoint is the namespace being used and is
462 specified for the full ONAP Kubernetes installation.
464 The following services will be required for the ONAP Policy Framework:
466 ================ ============================== =======================================================================
467 **Service** **Endpoint** **Description**
468 ================ ============================== =======================================================================
469 PAP https://policy-pap The PAP service, used for policy administration and deployment. See
470 :ref:`Policy Design and Development <design-label>` for details of the
472 PDP-X-\ *domain* https://policy-pdpx-\ *domain* A PDP service is defined for each PDP group. A PDP group is identified
473 by the domain on which it operates.
475 For example, there could be two PDP-X domains, one for admission
476 policies for ONAP proper and another for admission policies for VNFs of
477 operator *Supacom*. Two PDP-X services are defined:
479 | https://policy-pdpx-onap
480 | https://policy-pdpx-\ *supacom*
481 PDP-D-\ *domain* https://policy-pdpd-\ *domain*
482 PDP-A-\ *domain* https://policy-pdpa-\ *domain*
483 ================ ============================== =======================================================================
485 There is one and only one PAP service, which handles policy deployment, administration, and monitoring for all policies
486 in all PDPs and PDP groups in the system. There are multiple PDP services, one PDP service for each domain for which
489 2.3.2 The Policy Framework Information Structure
490 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
492 The following diagram captures the relationship between Policy Framework concepts at run time.
494 .. image:: images/RuntimeRelationships.svg
496 There is a one to one relationship between a PDP SubGroup, a Kubernetes PDP service, and the set of policies assigned to
497 run in the PDP subgroup. Each PDP service runs a single PDP subgroup with multiple PDPs, which executes a specific
498 Policy Set containing a number of policies that have been assigned to that PDP subgroup. Having and maintaining this
499 principle makes policy deployment and administration much more straightforward than it would be if complex relationships
500 between PDP services, PDP subgroups, and policy sets.
502 The topology of the PDPs and their policy sets is held in the Policy Framework database and is administered by the PAP service.
504 .. image:: images/PolicyDatabase.svg
506 The diagram above gives an indicative structure of the run time topology information in the Policy Framework database.
507 Note that the *PDP_SUBGROUP_STATE* and *PDP_STATE* fields hold state information for life cycle management of PDP groups
510 2.3.3 Startup, Shutdown and Restart
511 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
513 This section describes the interactions between Policy Framework components themselves and with other ONAP components at
514 startup, shutdown and restart.
516 2.3.3.1 PAP Startup and Shutdown
517 """"""""""""""""""""""""""""""""
519 The sequence diagram below shows the actions of the PAP at startup.
521 .. image:: images/PAPStartStop.svg
523 The PAP is the run time point of coordination for the ONAP Policy Framework. When it is started, it initializes itself
524 using data from the database. It then waits for periodic PDP status updates and for administration requests.
526 PAP shutdown is trivial. On receipt or a shutdown request, the PAP completes or aborts any ongoing operations and shuts
529 2.3.3.2 PDP Startup and Shutdown
530 """"""""""""""""""""""""""""""""
532 The sequence diagram below shows the actions of the PDP at startup. See also Section 4 of the
533 :ref:`Policy Design and Development <design-label>` page for the API used to implement this sequence.
535 .. image:: images/PDPStartStop.svg
537 At startup, the PDP initializes itself. At this point it is in PASSIVE mode. The PDP begins sending periodic Status
538 messages to the PAP. The first Status message initializes the process of loading the correct Policy Set on the PDP in
541 On receipt or a shutdown request, the PDP completes or aborts any ongoing policy executions and shuts down gracefully.
543 2.3.4 Policy Execution
544 ^^^^^^^^^^^^^^^^^^^^^^
546 Policy execution is the execution of a policy in a PDP. Policy enforcement occurs in the component that receives a
549 .. image:: images/PolicyExecutionFlow.svg
551 Policy execution can be *synchronous* or *asynchronous*. In *synchronous* policy execution, the component requesting a
552 policy decision requests a policy decision and waits for the result. The PDP-X and PDP-A implement synchronous policy
553 execution. In *asynchronous* policy execution, the component that requests a policy decision does not wait for the
554 decision. Indeed, the decision may be passed to another component. The PDP-D and PDP-A implement asynchronous polic
557 Policy execution is carried out using the current life cycle mode of operation of the PDP. While the actual
558 implementation of the mode may vary somewhat between PDPs of different types, the principles below hold true for all
561 ================== =====================================================================================================
562 **Lifecycle Mode** **Behaviour**
563 ================== =====================================================================================================
564 PASSIVE MODE Policy execution is always rejected irrespective of PDP type.
565 ACTIVE MODE Policy execution is executed in the live environment by the PDP.
566 SAFE MODE* Policy execution proceeds, but changes to domain state or context are not carried out. The PDP
567 returns an indication that it is running in SAFE mode together with the action it would have
568 performed if it was operating in ACTIVE mode. The PDP type and the policy types it is running must
569 support SAFE mode operation.
570 TEST MODE* Policy execution proceeds and changes to domain and state are carried out in a test or sandbox
571 environment. The PDP returns an indication it is running in TEST mode together with the action it has
572 performed on the test environment. The PDP type and the policy types it is running must support TEST
574 ================== =====================================================================================================
576 \* SAFE Mode and TEST Mode will be implemented in future versions of the Policy Framework.
578 2.3.5 Policy Lifecycle Management
579 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
581 Policy lifecycle management manages the deployment and life cycle of policies in PDP groups at run time. Policy sets can
582 be deployed at run time without restarting PDPs or stopping policy execution. PDPs preserve state for minor/patch
583 version upgrades and rollbacks.
585 2.3.5.1 Load/Update Policies on PDP
586 """""""""""""""""""""""""""""""""""
588 The sequence diagram below shows how policies are loaded or updated on a PDP.
590 .. image:: images/DownloadPoliciesToPDP.svg
592 This sequence can be initiated in two ways; from the PDP or from a user action.
594 1. A PDP sends regular status update messages to the PAP. If this message indicates that the PDP has no policies or
595 outdated policies loaded, then this sequence is initiated
597 2. A user may explicitly trigger this sequence to load policies on a PDP
599 The PAP controls the entire process. The PAP reads the current PDP metadata and the required policy and policy set
600 artifacts from the database. It then builds the policy set for the PDP. Once the policies are ready, the PAP sets the
601 mode of the PDP to PASSIVE. The Policy Set is transparently passed to the PDP by the PAP. The PDP loads all the policies
602 in the policy set including any models, rules, tasks, or flows in the policy set in the policy implementations.
604 Once the Policy Set is loaded, the PAP orders the PDP to enter the life cycle mode that has been specified for it
605 (ACTIVE/SAFE*/TEST*). The PDP begins to execute policies in the specified mode (see section 2.3.4).
607 \* SAFE Mode and TEST Mode will be implemented in future versions of the Policy Framework.
611 2.3.5.2 Policy Rollout
612 """"""""""""""""""""""
614 A policy set steps through a number of life cycle modes when it is rolled out.
616 .. image:: images/PolicyRollout.svg
618 The user defines the set of policies for a PDP group. It is deployed to a PDP group and is initially in PASSIVE mode.
619 The user sets the PDP Group into TEST mode. The policies are run in a test or sandboxed environment for a period of
620 time. The test results are passed back to the user. The user may revert the policy set to PASSIVE mode a number of times
621 and upgrade the policy set during test operation.
623 When the user is satisfied with policy set execution and when quality criteria have been reached for the policy set, the
624 PDP group is set to run in SAFE mode. In this mode, the policies run on the target environment but do not actually
625 exercise any actions or change any context in the target environment. Again, as in TEST mode, the operator may decide to
626 revert back to TEST mode or even PASSIVE mode if issues arise with a policy set.
628 Finally, when the user is satisfied with policy set execution and when quality criteria have been reached, the PDP group
629 is set into ACTIVE state and the policy set executes on the target environment. The results of target operation are
630 reported. The PDP group can be reverted to SAFE, TEST, or even PASSIVE mode at any time if problems arise.
632 \* SAFE Mode and TEST Mode will be implemented in future versions of the Policy Framework. In current versions, policies
633 transition directly from PASSIVE mode to ACTIVE mode.
635 2.3.5.3 Policy Upgrade and Rollback
636 """""""""""""""""""""""""""""""""""
638 There are a number of approaches for managing policy upgrade and rollback. Upgrade and rollback will be implemented in
639 future versions of the Policy Framework.
641 The most straightforward approach is to use the approach described in section :ref:`policy-rollout` for upgrading and
642 rolling back policy sets. In order to upgrade a policy set, one follows the process in :ref:`policy-rollout` with the
643 new policy set version. For rollback, one follows the process in :ref:`policy-rollout` with the older policy set, most
644 probably setting the old policy set into ACTIVE mode immediately. The advantage of this approach is that the approach is
645 straightforward. The obvious disadvantage is that the PDP group is not executing on the target environment while the new
646 policy set is in PASSIVE, TEST, and SAFE mode.
648 A second manner to tackle upgrade and rollback is to use a spare-wheel approach. An special upgrade PDP group service is
649 set up as a K8S service in parallel with the active one during the upgrade procedure. The spare wheel service is used to
650 execute the process described in :ref:`policy-rollout`. When the time comes to activate the policy set, the references
651 for the active and spare wheel services are simply swapped. The advantage of this approach is that the down time during
652 upgrade is minimized, the spare wheel PDP group can be abandoned at any time without affecting the in service PDP group,
653 and the upgrade can be rolled back easily for a period simply by preserving the old service for a time. The disadvantage
654 is that this approach is more complex and uses more resources than the first approach.
656 A third approach is to have two policy sets running in each PDP, an active set and a standby set. However such an
657 approach would increase the complexity of implementation in PDPs significantly.
659 2.3.6 Policy Monitoring
660 ^^^^^^^^^^^^^^^^^^^^^^^
662 PDPs provide a periodic report of their status to the PAP. All PDPs report using a standard reporting format that is
663 extended to provide information for specific PDP types. PDPs provide at least the information below:
665 ===================== ===============================================================================
666 **Field** **Description**
667 ===================== ===============================================================================
668 State Lifecycle State (PASSIVE/TEST*/SAFE*/ACTIVE)
669 Timestamp Time the report record was generated
670 InvocationCount The number of execution invocations the PDP has processed since the last report
671 LastInvocationTime The time taken to process the last execution invocation
672 AverageInvocationTime The average time taken to process an invocation since the last report
673 StartTime The start time of the PDP
674 UpTime The length of time the PDP has been executing
675 RealTimeInfo Real time information on running policies.
676 ===================== ===============================================================================
678 \* SAFE Mode and TEST Mode will be implemented in future versions of the Policy Framework.
680 Currently, policy monitoring is supported by PAP and by pdp-apex. Policy monitoring for all PDPs will be supported in
681 future versions of the Policy Framework.
683 2.3.7 PEP Registration and Enforcement Guidelines
684 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
686 In ONAP there are several applications outside the Policy Framework that enforce policy decisions based on models
687 provided to the Policy Framework. These applications are considered Policy Enforcement Engines (PEP) and roles will be
688 provided to those applications using AAF/CADI to ensure only those applications can make calls to the Policy Decision
689 APIs. Some example PEPs are: DCAE, OOF, and SDNC.
691 See Section 3.4 of the :ref:`Policy Design and Development <design-label>`
692 for more information on the Decision APIs.
694 3. APIs Provided by the Policy Framework
695 ========================================
697 See the :ref:`Policy Design and Development <design-label>` page.
702 ================================= ==================================================================================
703 PAP (Policy Administration Point) A component that administers and manages policies
704 ================================= ==================================================================================
705 PDP (Policy Deployment Point) A component that executes a policy artifact (One or many?)
706 PDP_<> A specific type of PDP
707 PDP Group A group of PDPs that execute the same set of policies
708 Policy Development The development environment for policies
709 Policy Type A generic prototype definition of a type of policy in TOSCA, see the
710 :ref:`TOSCA Policy Primer <tosca-label>`
711 Policy An executable policy defined in TOSCA and created using a Policy Type, see the
712 :ref:`TOSCA Policy Primer <tosca-label>`
713 Policy Set A set of policies that are deployed on a PDP group. One and only one Policy Set is
714 deployed on a PDP group
715 ================================= ==================================================================================