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The CLAMP Kubernetes Participant performs the helm Helm chart installation and LCM for k8s Kubernetes (K8S) microservices that take part in Control looploops.  It implements Participantthe participant-Intermediary API to receive events from DMaap the CLAMP runtime and then interacts with Helm CLI. It acts as a wrapper around the Helm Cli CLI to manage helm Helm charts and K8s pods deployed in the cluster.

Helm 3 overview:

In Helm3, helm cli the Helm CLI acts as an interface for towards a Kubernetes cluster, and allows the user to deploy and manage helm charts. It also supports configuring configuration of multiple chart repositories to for the helm client and enables access the to charts from those repos for installation of K8S microservices. The repositories can be a local chart server servers running on the same machine as well a or third party chart server servers running elsewhere.   The URL of the a chart server can be configured on the helm Helm repo list to permit access the hosted helm charts. User can add a repository and push helm charts under the repository via helm cli to Helm charts hosted in those repos. Users can add repositories and push Helm charts to the repositories via Helm CLI commands.

Example: configured Configured chart repos and the available charts are listed via helm cli:the Helm CLI

CLAMP Kubernetes Participant Architecture in Istanbul:

Prerequisites for kubernetes Kubernetes participant:

• Kubernetes cluster running.
• Helm cli running.
• Operator Currently, the operator is expected to store the helm charts in any of the configured helm repositories via helm cli command (or) the charts should be kept provide the repository information where the helm chart is available, via TOSCA /REST end point or ensure that the charts are available on the local storage directory of kubernetes-participant. (This directory is a preconfigured path specified on the participant config that acts as a local chart repository). Charts can be onboarded to local chart repository via REST endpoints.

Note: Incase of containerization of kubernetes When using the Kubernetes participant in upcoming releasedocker container, the kubeconfig config file of the required kubernetes cluster should be copied to the k8s-participant's docker container's home directory under /.kube folder  in order to make helm cli the participant work with the external cluster outside.

In the Istanbul release, the CLAMP Kubernetes participant in control loop supports supports the following methods for installation of helm charts in below ways via CLAMP:

• Install Installation of a helm Helm chart that is present in the same local file system as where the kubernetes participant is hosted.
• Install Installation of Helm charts from the helm repositories that are configured on the helm client.  

Kubernetes-participant acts as an interface between DMaap and Helm Client.  

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• any remote helm repositories. (The remote repository details needs to be passed on via TOSCA or REST API to the kubernetes participant)

The CLAMP Kubernetes participant acts as a mediator between the CLAMP runtime and the Helm Client.

While commissioning a control loop, the Helm chart parameters are passed via TOSCA template to the control loop runtime database. And when the control loop is instantiated, kubernetes-the Kubernetes participant receives control loop element update event from DMaap, it the CLAMP runtime. It then invokes the helm Helm client running on the host machine to install the corresponding helm Helm charts associated with the affected control loop elements. The k8s- The Kubernetes participant gets the parameters (chart name, version, release name and namespace) of the chart from the control loop runtime.  If the repository of the chart had not been specified in the TOSCA, it performs  performs a "chart lookup"   on all the configured repositories of in the helm Helm client as well as on the local chart directory where the helm Helm charts are may be manually onboarded by the operator. It fetches the appropriate repository info and installs the chart via the helm cliCLI.

The k8s-Kubernetes participant takes care of creating a namespace on the cluster if required, fetching the helm Helm chart from the available repositories, installing and uninstalling the chart in to the cluster. In the upcoming releasereleases, additional options will be supported in control loop CLAMP for onboarding the helm Helm charts to the repositories via TOSCA (both configured helm Helm repos and local chart directory) before instantiation. (Under discussion)                                                                              

The code block below shows a Sample TOSCA  service template passed during commissioning of control loops. Below are the ways , the charts Charts can be commissioned via TOSCA . in the following mentioned ways:

• Chart parameters: chartId(name, version),

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• releaseName and namespace are mandatory in TOSCA.
• Repository can be specified with either

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• remote helm repository

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• or any local directory where the helm charts are available.

(Note: Repository name is an optional parameter in control loop TOSCA template. If not specified, the k8s-particpant Kubernetes participant will do a look - up on the available local chart storage and configured helm repos)

org.onap.domain.database.HelloWorld_K8SMicroserviceControlLoopElement:
# Chart from local anyfile chartsystem repository(pre configuredonboarded onvia helmREST clientAPI).
version: 1.2.3
type: org.onap.policy.clamp.controlloop.K8SMicroserviceControlLoopElement
type_version: 1.0.0
description: Control loop element for the K8S microservice for Hello World
properties:
provider: ONAP
participant_id:
name: org.onap.k8s.controlloop.K8SControlLoopParticipant
version: 2.3.4
chart:
release_namereleaseName: helloworld
chart_
chartId: 
  name: hello
  version: 0.1.0
repository: chartMuseum
namespace: onap

org.onap.domain.database.PMSH_K8SMicroserviceControlLoopElement:
# Chart from localany fileremote systemrepository

version: 1.2.3
type: org.onap.policy.clamp.controlloop.K8SMicroserviceControlLoopElement
type_version: 1.0.0
description: Control loop element for the K8S microservice for PMSH
properties:
provider: ONAP
participant_id:
name: org.onap.k8s.controlloop.K8SControlLoopParticipant
version: 2.3.4
chart:
release_name: pmshmicroservice
chart_
chartId:
  name: dcae_pmsh
  version: 8.0
repository: 
  repoName: chartMuseum
  address: 172.1.0
repository: /home/oom/helm-charts/PMSH125.12.1
  port: 8082
  protocol: http
  username: username
  password: password
namespace: onap

org.onap.domain.database.Local_K8SMicroserviceControlLoopElement:
# Chart installation without passing repository name (chart lookup happens on local chart storage and preconfigured helm repos)
version: 1.2.3
type: org.onap.policy.clamp.controlloop.K8SMicroserviceControlLoopElement
type_version: 1.0.0
description: Control loop element for the K8S microservice for any chart
properties:
provider: ONAP
participant_id:
name: org.onap.k8s.controlloop.K8SControlLoopParticipant
version: 2.3.4
chart:
release_name: nginxms
chart_name: nginx-ingress
version: 0.9.1
namespace: onap

The Kubernetes participant receives messages through the participant-intermediary common code, and handles them by invoking the Kubernetes Open API via the Helm client. For example, When a ControlLoopUpdate message is received by Kubernetes participant,  the control loop element state changed from UNINITIALISED to PASSIVE, Kubernetes-participant triggers Kubernetes Open API and installs the HELM charts on the cluster.

Run CLAMP Kubernetes Participant command line using Maven

mvn spring-boot:run -Dspring-boot.run.arguments="--topicServer=localhost"

Run CLAMP Kubernetes Participant command line using Jar

java -jar -DtopicServer=localhost target/policy-clamp-participant-impl-kubernetes-6.1.2-SNAPSHOT.jar

REST APIs on Kubernetes participant:

Kubernetes participant can also be installed as a standalone application which exposes REST endpoints for onboarding, installing, uninstalling helm charts from local chart directories.

Image Added

K8s-participant User guide (PMSH usecase)