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| -rw-r--r-- | docs/scenario-lifecycle/scenario-overview.rst | 165 |
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diff --git a/docs/scenario-lifecycle/scenario-overview.rst b/docs/scenario-lifecycle/scenario-overview.rst index 9c9c508..4a7ff7a 100644 --- a/docs/scenario-lifecycle/scenario-overview.rst +++ b/docs/scenario-lifecycle/scenario-overview.rst @@ -14,77 +14,146 @@ Overview Problem Statement: ^^^^^^^^^^^^^^^^^^^ -OPNFV provides the NFV reference platform in different variants, using different -upstream open source projects. -In many cases this includes also different upstream projects providing similar or -overlapping functionality. +OPNFV provides the NFV reference platform in different variants, where +each variant is called a "scenario". -OPNFV introduces scenarios to define various combinations of components from upstream -projects or configuration options for these components. +OPNFV introduces scenarios in order to provide a way to deploy the stack +using different combinations of upstream components, or to provide +different sets of pre-defined configuration options for these +components. -The number of such scenarios has increased over time, so it is necessary to clearly -define how to handle the scenarios. +In some cases a scenario is introduced in order to provide isolation of +a specific development effort from other ongoing development efforts, +similar to the purpose of a branch in a code repository. -Introduction: +A certain amount of effort and resources is required in order to include +a scenario in a release. The number of scenarios has increased over +time, so it is necessary to identify ways to manage the number of +scenarios and to avoid that their number grows infinitely. To enable +this, we have to clearly define how to handle the lifecycle of +scenarios, i.e. how to create, how to terminate, etc. + + +Scenario types: ^^^^^^^^^^^^^^^^^^^ Some OPNFV scenarios have an experimental nature, since they introduce -new technologies that are not yet mature enough to provide a stable release. -Nevertheless there also needs to be a way to provide the user with the -opportunity to try these new features in an OPNFV release context. +new technologies or features that are not yet mature or well integrated +enough to provide a stable release. Nevertheless there also needs to be +a way to provide the user with the opportunity to try these new features +in an OPNFV release context. Other scenarios are used to provide stable environments for users -that wish to build products or live deployments on them. +desiring a certain combination of upstream components or interested in +particular capabilities or use cases. -OPNFV scenario lifecycle process will support this by defining two types of scenarios: +The new OPNFV scenario lifecycle process proposed herein will support +this by defining two types of scenarios: * **Generic scenarios** cover a stable set of common features provided - by different components and target long-term usage. -* **Specific scenarios** are needed during development to introduce new upstream - components or new features. - They are intended to merge with other specific scenarios - and bring their features into at least one generic scenario. - -OPNFV scenarios are deployed using one of the installer tools. -A scenario can be deployed by multiple installers and the result will look -very similar but different. The capabilities provided by the deployments -should be identical. Results of functional tests should be the same, +by different components and target long-term usage and maintenance of +the scenario. Only stable versions of upstream components are allowed to +be deployed in a generic scenario. Across all generic scenarios in a +given OPNFV release, the same version of a given upstream component +should be deployed. Creation of generic scenarios and promotion of +specific to generic scenario requires TSC approval, see section 5. +Generic scenarios will get priority over specific scenarios in terms of +maintenance effort and CI resources. + +* **Specific scenarios** are needed during development to introduce new +upstream components or new features. They are typically derived from a +generic scenario and are intended to bring their features back into the +parent generic scenario once they are mature enough. It is also possible +that multiple specific scenarios are merged before bringing them back to +the parent scenario, for example in order to test and develop the +integration of two specific features in isolation. Specific scenarios +can consume unreleased upstream versions or apply midstream patches. +Creation of specific scenarios is not gated, but if a project intends to +release a specific scenario, it has to indicate that in its release plan +at milestone MS1. The scenario itself can be created at any time, by +means of a simple request by a PTL to the release manager. + +OPNFV scenarios are deployed using one of the OPNFV installer tools. +Deploying a scenario will normally be supported by multiple installers. +The capabilities provided by the resulting deployments should be +identical. The set of tests to run and their results should be the same, independent of the installer that had been used. Performance or other -behavioral aspects could be different. -The scenario lifecycle process will also define how to document which installer -can be used for a scenario and how the CI process can trigger automatic deployment -for a scenario via one of the supported installers. +behavioral aspects outside the scope of existing OPNFV tests could be +different. + -When a developer decides to define a new scenario, he typically will take one -of the existing scenarios and does some changes, such as: +Parent-child and sibling relations: +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +When a developer decides to define a new scenario, he typically will +take one of the existing scenarios and do some changes, such as: * add additional components * change a deploy-time configuration -* use a component in a more experimental version +* use a component in a more experimental version or with midstream +patches applied + +In this case the already existing scenario is called a "parent" and the +new scenario would be a "child". + +Typically parent scenarios are generic scenarios, but it is possible to +derive from specific scenarios as well. it is expected that the child +scenario develops its additions over some time up to a sufficient +maturity, and then merges back to the parent. This way a continuous +evolution of the generic scenarios as well as a manageable overall +number of scenairos is ensured. + +In some cases a child scenario will diverge from its parent in a way +that cannot easily be combined with the parent. Therefore, is is also +possible to "promote" a scenario from specific to generic. If this is +foreseeable upfront, the specific scenario can also be derived as a +sibling rather that child. + +Promoting a scenario from specific to generic or creating a new generic +scenario requires TSC approval. This document defines a process for +this, see section 5. -In this case the already existing scenario is called a "parent" and the new -scenario a "child". -Typically parent scenarios are generic scenarios, but this is not mandated. -In most times the child scenario will develop the new functionality over some -time and then try to merge its configuration back to the parent. -But in other cases, the child will introduce a technology that cannot easily -be combined with the parent. -For this case this document will define how a new generic scenario can be created. +Scenario deployment options: +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ -Many OPNFV scenarios can be deployed in a HA (high availability) or non-HA -configuration. -HA configurations deploy some components according to a redundancy model, -as the components support. -In these cases multiple deployment options are defined for the same scenario. +Many OPNFV scenarios can be deployed in different variants that do not +justify creation of separate scenarios. An example would be HA (high +availability) or non-HA configuration of otherwise identical scenarios. +HA configurations deploy some components according to a redundancy +model. Deployment options will also be used if the same scenario can be +deployed on multiple types of hardware, i.e. Intel and ARM. -Deployment options will also be used if the same scenario can be deployed -on multiple types of hardware, i.e. Intel and ARM. +In these cases multiple deployment options are defined for the same +scenario. The set of distinguishable deployment option types (e.g. +redundancy, processor architecture, etc.) will be pre-determined and +each scenario will have to define at least one option for each option +type. + +It is emphasized that virtual deployments vs. bare-metal deployments are +intentionally not considered as deployment options. This should be a +transparent feature of the installer based on the same scenario +definition. + +For generic scenarios, there are certain expectations on the set of +supported deployment options, e.g. a generic scenario should support at +least an HA deployment and preferably both HA and non-HA. + + +Scenario descriptor file: +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Every scenario will be described in a scenario descriptor yaml file. This file shall contain all the necessary information for different users, such as the installers (which components to deploy etc.), -the ci process (to find the right resources), -the test projects (to select correct test cases), etc. +the ci process (resource requirements in order to identify the right pod, machines, etc.). + +The scenario descriptor file will also document which installer +can be used for a scenario and how the CI process can trigger automatic deployment +for a scenario via one of the supported installers. + + +MANO scenarios: +^^^^^^^^^^^^^^^^^^^^^^^^^^^^ In early OPNFV releases, scenarios covered components of the infrastructure, that is NFVI and VIM. |