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- An initContainer that waits for the other components that the service component needs, such as AAF and Consul In the current Cloudify implementation, we can guarantee that a service component won't be deployed before these other components are ready. We can't make that guarantee for Helm.
- An initContainer that puts the component configuration into Consul (see next section for details).
The configuration parameters for the component (the image name, log directory, TLS parameters) currently come from the Cloudify blueprint–either directly or through an inputs file. With Helm deployment, these parameters will move into the values.yaml file for the component.
Because there is a common structure to the Kubernetes Deployments for all service components, we should create a Helm template for a DCAE service component Deployment. The Deployment will be configured for a specific service component through the parameters in the values.yaml file. The OOM common Helm templates do not include a template for a Deployment, but they do include templates for various parts of a deployment (for instance, a logging sidecar). The DCAE service component Deployment template should use OOM common templates wherever possible.
Setting up the component configuration in Consul
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When the Helm chart for the service component is deployed, the initContainer will run and will store the application configuration into Consul. When the service component starts, the configuration information will be available
in Consul.
Kubernetes Service
The k8splugin currently creates a ClusterIP service if a component exposes IP ports within the cluster and a NodePort service plus a ClusterIP service if the component exposes a port outside the cluster. In the latter case, the ClusterIP service is redundant–a NodePort service will also expose a component within the cluster. The OOM common templates include a template for a Service. We can use that template to create a Service for the component, with all of the details configured in the values.yaml file. The k8splugin does not currently allow for exposing a component via an Ingress. Supporting Ingresses should be investigated as part of the move to Helm.
Extended capabilities
Using DMaaP
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Using a Postgres database
ONAP already has a Helm-based mechanism for deploying instances of Postgres and setting up credentials for client access. We use this mechanism to create the DCAE postgres database already. The drawback to this approach is that it creates a separate instance of Postgres each time it is used. There has been work on setting up shared instances of databases in ONAP, but so far Postgres has not been included in those efforts.
As we move DCAE service component deployment to Helm, we should make use of the ONAP project-wide Helm mechanisms. If DCAE has certain special requirements, we should work to enhance the project-wide mechanisms.
Implementation Phases
Service components deployed at DCAE installation time
As of the Guilin release, we are deploying 6 service components at DCAE installation time, via a script that runs on the DCAE k8s-bootstrap-container:
tcagen2 (org.onap.dcaegen2.analytics.tca-gen2.dcae-analytics-tca-web)
ves-tls (org.onap.dcaegen2.collectors.ves.vescollector)
prh (org.onap.dcaegen2.services.prh.prh-app-server)
hv-ves (org.onap.dcaegen2.collectors.hv-ves.hv-collector-main)
holmes_rules (holmes/rule-management)
holmes_engine (holmes/engine-management)
The first four components do not use any extended capabilities (DMaaP, policies, Postgres database), so they can be moved to a Helm-based deployment without implementing solutions for the extended capabilities. The last two components use the DCAE postgres database. Moving these components will require some alternative solution for the database. The Holmes components are managed by the Holmes project, which is separate from the DCAE project. The Holmes project will need to address the issue of handling the Postgres database differently.
For ONAP R8 ("Honolulu"), we propose creating the Helm templates and charts needed to deploy the first four components on the list above.
Service components deployed on demand
Helm Chart Management
Currently nearly all of the Helm charts for ONAP, including the charts for the DCAE platform components, are stored in a single source tree under the OOM repository. Typically the charts are built and stored into a locally-running Helm repository server instance. This works reasonably well for deploying the base ONAP platform in a single installation step. Most DCAE service components are deployed and undeployed after the initial ONAP installation. The charts for DCAE service components should be managed separately from the OOM tree, with charts for released versions of service components being pushed into a public ONAP Helm repository.