[helm] add kube-state-metric subchart dependency

[pkoutsovasilis]

What does this PR do?

This PR refactors the Elastic Agent Helm chart to include the kube-state-metrics (KSM) chart as a subchart dependency. The changes enable users to seamlessly deploy KSM alongside the Elastic Agent for all different deployment options, improving the out-of-the-box experience for Kubernetes monitoring.

Key changes include:

• Addition of the KSM Helm chart as a subchart dependency.
• Introduction of values that allow enabling or disabling KSM deployment (kube-state-metrics.enabled) and deploying Elastic Agent as a sidecar container to the former (kubernetes.state.agentAsSidecar.enabled)
  • PS: now that kube-state-metrics derive from another subchart deploying elastic-agent through ECK as a sidecar is not feasible. values.schema.json has been updated to prevent such configuration
• Refactoring of the Helm chart structure to incorporate KSM configurations and clean-up unused code.
  • The templates that regard the input of kube-state-metrics in kubernetes integration got significantly reduced resulting in an easier to follow code
  • The templates that regard the k8s tuning of each preset based on the Helm values got migrated to a separate folder to promote segregation from input-related templates, thus resulting in an easier to follow code

This PR consists of 3 commits:

• 546ec26 just introduce the kube-state-metric subchart dependency
• 27748fa the actual changes of this PR
• a019dbf examples showcasing the new functionality

since a019dbf, which is the main change of this PR, is +529 additions -1268 deletions I deem that this PR complies with the team PR policies but happy to try to split it up in smaller chunks if it doesn't 🙂

Why is it important?

This PR is important because it enhances the Elastic Agent Helm chart to simplify the deployment and management of Kubernetes monitoring. By including kube-state-metrics as a subchart dependency, the PR significantly reduces user friction and ensures better alignment with Kubernetes integration requirements.

The refactoring also:

• Improves maintainability by reducing template complexity and segregating logic for better readability.
• Provides flexibility for users to enable or disable KSM and enable or disable embedding elastic-agent as a sidecar to the former, catering to diverse use cases.

Checklist

• I have read and understood the pull request guidelines of this project.
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Disruptive User Impact

This PR introduces a new default behavior that includes the kube-state-metrics chart as a dependency. By default:

• kube-state-metrics is deployed. Users must explicitly disable it by setting kube-state-metrics.enabled=false to opt out of deploying
• all kube-state-metrics related metrics are now captured by the cluster-wide agent preset. Users opting to deploy elastic-agent as a sidecar to kube-state-metrics must explicitly enable it in the values file by setting kubernetes.state.agentAsSidecar.enabled=true.
• Unsupported configurations, such as deploying Elastic Agent as a sidecar to KSM managed by ECK, are now restricted.

For users upgrading existing installations, ksmSharded preset is gonna be uninstalled and their kube-state-metrics related flow will follow the logic above

How to test this PR locally

• Follow one of the newly introduced examples
• Run k8s integration tests

  mage integration:auth
  PLATFORMS=linux/arm64 EXTERNAL=true SNAPSHOT=true PACKAGES=docker mage -v package 
  INSTANCE_PROVISIONER=kind STACK_PROVISIONER=stateful K8S_VERSION=v1.31.1 SNAPSHOT=true mage integration:kubernetes
  

Related issues

• Relates Fleet managed Elastic Agent installation with Helm Chart missing topics ingest-docs#1531

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube

[elasticmachine]

Pinging @elastic/elastic-agent-control-plane (Team:Elastic-Agent-Control-Plane)

[blakerouse]

Looks good to me. Just a question on the dependency keeping in sync with release.

[blakerouse]

Are we going to add any automation to keep this in-sync with released versions or is this going to be manual?

[pkoutsovasilis]

good point 👌 I have to investigate how we could employ renovate to do that 🙂 do you believe this could be a follow-up PR?

[blakerouse]

absolutely, in a follow up

this is already large enough ;-)