Refactor opensearch-cluster helm chart

[evheniyt]

Description

We found that the current opensearch-cluster helm chart supports only OpenSearchCluster configuration, also configuration itself is very limited because not all possible options were defined in the template.
For our needs, we have decided to improve this helm chart and think that our changes could be useful for the community.

The main differences in the new helm chart:

• Supports all existing CRDs
• Includes auto-generated README.md file with description for all possible configuration values
• Includes Ingress configuration for Opensearch and Dashboards
• Values.yaml has examples of operator-specific configurations, making it easier for users to understand what to set
• Easy to maintain and extend

We were trying to build this chart by following the next logic. We didn't try to template all possible configurations for CRDs, instead, we relied on official parameters supported by specific sections of the CRD, e.g.

Instead of doing this:

  {{- if .Values.opensearchCluster.bootstrap }}
  bootstrap:
    {{- if .Values.opensearchCluster.bootstrap.additionalConfig }}
    additionalConfig:
      {{ toYaml .Values.opensearchCluster.bootstrap.additionalConfig | nindent 6 }}
    {{- end }}
  {{- end }}
  {{- if .Values.opensearchCluster.initHelper }}

We did:

  {{- with .Values.cluster.bootstrap }}
  bootstrap: {{ . | toYaml | nindent 4 }}
  {{- end }}

And defined all possible configuration options inside the .Values.cluster.bootstrap.

Pros of such logic:

• it helps simplify the maintenance of the chart, when a new config option is added you just need to add its default value to values.yaml file. And even if for some reason it wasn't added, users still could use it;
• all existing and new configuration options will be available for users;
• configuration options have the same format and naming as it is defined in the operator doc, so users will be not confused by different naming in helm and off doc.
• it allows to automatically check all defined options, so when users make a typo or put invalid configuration they will receive an error during deployment, helping them to understand what they did wrong.

If you apply it, I could help with maintaining this helm chart by fixing bugs, adding new features, etc.

Issues Resolved

Closes #699
Closes #9

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[evheniyt]

FYI as this PR was prepared a few months ago it didn't include some templates for the CRDs. If you will give it a green light in terms of concept and implementation I will add all missing templates.

[prudhvigodithi]

Hey @evheniyt thanks for your contribution, I like the idea to control the yaml files using the helm that can be used to create the cluster via the operator, can you include all the CRD's and fix the conflicts, we can go ahead and merge it.

Adding @bbarani @salyh @jochenkressin @pchmielnik @bbarani

[evheniyt]

Sure, I will add all the missing CRDs soon. Also, will need to add upgrade instructions.
@prudhvigodithi what about chart version? currently, it is equal to operator version. Do you think we should continue with this approach or we could have a different version for chart?
With different version for chart it will be simpler to set it 3.0.0 meaning that there are breaking changes.

[prudhvigodithi]

Thanks @evheniyt with existing setup and release process, the helm charts are updated to the appVersion (operator version) https://github.com/opensearch-project/opensearch-k8s-operator/blob/main/.github/workflows/release.yaml#L26-L31.

We should seperate out this sooner to ensure the helm charts development and release is fast paced. WDYT @salyh @jochenkressin @pchmielnik @swoehrl-mw ?

[swoehrl-mw]

@prudhvigodithi

We should seperate out this sooner to ensure the helm charts development and release is fast paced.

There is something to be said for keeping the versioning of cluster chart and operator the same to make it clear which versions match and are compatible. But on the other hand I can understand the cluster chart might need a faster/different release cycle than the operator.

[salyh]

We should seperate out this sooner to ensure the helm charts development and release is fast paced. WDYT @salyh @jochenkressin @pchmielnik @swoehrl-mw ?

I agree

[evheniyt]

Added OpenSearchISMPolicy template

[evheniyt]

I have updated Readme.

Also, I have tested helm chart upgrade process from v2 to v3 with default config from values.yaml. In general, because the new version of the helm chart has the same labels, annotations and follows the same default logic for cluster name, the upgrade from v2 to v3 (with default values) didn't trigger any resource redeployments.

Now it's ready for review @prudhvigodithi @swoehrl-mw @salyh