Elastic Stack Helm chart upgrade and configuration changes documentation

[eedugon]

This PR adds documentation for Elastic Stack Helm chart (provided by ECK) users to know how to upgrade and apply configuration changes.

As you'll see, certain parts of the content are not purely about ECK and Elastic Stack specifics, but a bit about how Helm works and educates the reader in areas that are not purely ours.

I've tried to fit the content to our exact domain (Elastic Stack), but giving enough information to understand the basics.

Closes #3591

After admin-docs review we will need to find devs to review the content.
Update: ready for review by ECK team.

[github-actions]

✅ Vale Linting Results

No issues found on modified lines!

---

The Vale linter checks documentation changes against the Elastic Docs style guide.

To use Vale locally or report issues, refer to Elastic style guide for Vale.

[github-actions]

🔍 Preview links for changed docs

• deploy-manage/deploy/cloud-on-k8s/install-using-helm-chart.md
• deploy-manage/deploy/cloud-on-k8s/managing-deployments-using-helm-chart.md
• deploy-manage/upgrade/deployment-or-cluster/upgrade-on-eck.md

[shainaraskas]

although I don't know too much about kubernetes / helm, none of this struck me as superfluous information. I think you did a good job of adding the right amount of info but keeping it task-based for the ECK context.

approving because this is nearly perfect - whatever you do from here is mergeable from my pov.

one thing that might be missing: do I need a specific version of the helm chart to access later versions of the stack? e.g. is upgrading the helm chart version a prerequisite? If that is the case, I believe it is not clear.

[shainaraskas]

changes look great. two tiniest suggestions

[eedugon]

This PR is now ready for review by ECK team! cc: @elastic/cloud-k8s ;)

[pebrc]

LGTM. My only note is that we are venturing a bit far into the realm of explaining Helm which is a third-party tool and mastering it is not something Elastic can necessarily support to the full extent.

[eedugon]

thanks @pebrc

LGTM. My only note is that we are venturing a bit far into the realm of explaining Helm which is a third-party tool and mastering it is not something Elastic can necessarily support to the full extent.

Completely agreed, that’s a fair point.

I’ve tried to keep the scope limited to Helm usage as it relates to the eck-stack chart and the Elastic Stack, and to avoid going into Helm concepts beyond what’s needed for this chart. But it's true that some small sentences could be felt unnecessary, or providing examples with both methods (--set and -f) to configure the same.

Anyway I've updated a bit the intro of the document to state that we expect familiarity with Helm and we are not providing a comprehensive introduction to Helm itself.

And I've also updated the important note telling users to use same values used during the installation to a simple recommendation, refering the readers to helm upgrade documentation for more details on how helm handle values of existing releases.

On the other hand, I think this type of guide (trying not to be a helm guide but providing some basics when needed) could also help reduce requests for help (SDHs).

[shainaraskas]

changes look good to me with a couple of small notes that are mostly just my opinion

[shainaraskas]

I suggest moving this scope note out of this intro paragraph because it's not core to the doc. maybe put it as a bullet in the tip. Also avoid semicolons

[eedugon]

ok, reverted intro to original text, and improved the paragraph that talked about the document, now this fits in the right place:

The chart enables you to deploy the core components ({{es}} and {{kib}}) together, along with other {{stack}} applications if needed, under the same chart release. The following sections guide you through common installation, configuration, and upgrade use cases and assume basic familiarity with Helm. It does not provide a comprehensive introduction to Helm itself.

[shainaraskas]

why is this different from required arguments? I think the old sentence was clearer