Fix GKE autopilot reco

[shainaraskas]

Summary

Followup to elastic/cloud-on-k8s#8971 - @pebrc caught that gke autopilot will reject this setting because it does not match the approved DaemonSet

based on @barkbay's work, I've added instructions for using a custom ComputeClass as an alternative to using a DaemonSet.

Generative AI disclosure

1. Did you use a generative AI (GenAI) tool to assist in creating this contribution?

• Yes
• No

[github-actions]

Vale Linting Results

Summary: 4 suggestions found

💡 Suggestions (4)

File	Line	Rule	Message
deploy-manage/deploy/cloud-on-k8s/deploy-eck-on-gke-autopilot.md	70	Elastic.Wordiness	Consider using 'before' instead of 'prior to'.
deploy-manage/deploy/cloud-on-k8s/virtual-memory.md	142	Elastic.Wordiness	Consider using 'impossible' instead of 'not possible'.
deploy-manage/deploy/cloud-on-k8s/virtual-memory.md	165	Elastic.Wordiness	Consider using 'because' instead of 'since'.
deploy-manage/deploy/cloud-on-k8s/virtual-memory.md	166	Elastic.Wordiness	Consider using 'because' instead of 'since'.

[github-actions]

🔍 Preview links for changed docs

• deploy-manage/deploy/cloud-on-k8s/deploy-eck-on-gke-autopilot.md
• deploy-manage/deploy/cloud-on-k8s/virtual-memory.md

[pebrc]

Looks good. I few small clarifications.

In general I feel like this is quite a tricky subject to navigate and present with different recommendations per Elasticsearch version and now we added another layer of vendor specific recommendations (for GKE/Autopilot). We are however now quite inconsistent with the vendor specific recommendations (only GKE/Autopilot is covered) but one could ask why we do not cover other vendors. AWS EKS with custom AMIs or LaunchTemplates or Azure AKS --linux-os-config provide similar options. Where do we draw the line?

[shainaraskas]

@pebrc

In general I feel like this is quite a tricky subject to navigate and present with different recommendations per Elasticsearch version and now we added another layer of vendor specific recommendations (for GKE/Autopilot). We are however now quite inconsistent with the vendor specific recommendations (only GKE/Autopilot is covered) but one could ask why we do not cover other vendors. AWS EKS with custom AMIs or LaunchTemplates or Azure AKS --linux-os-config provide similar options. Where do we draw the line?

this specifically is addressing a limitation that this specific combo of vendor/version has, so I don't think it's too strange that we go a little deeper in this one area.

we could hint that there are other methods for other vendors that are untested (unsupported?), but these are "known good" approaches, if you'd like, perhaps as a followup PR

[eedugon]

Looks great, some minor suggestions added.

[eedugon]

That sentence is a bit difficult to digest.... the when unset is not clear (what can be set that uses a hostPath? Probably the data directory of the beat or the state directory of the Elastic agent, but the unset statement feels weird).

Not sure if this sounds better or feels easier.... @pebrc, @shainaraskas , wdyt?

Suggested change

When running Elastic Agent and Beats within GKE Autopilot there are storage constraints to be considered. No `HostPath` volumes are allowed, which the ECK operator defaults to when unset for both `Deployments` and `DaemonSets`. Instead use [Kubernetes ephemeral volumes](https://kubernetes.io/docs/concepts/storage/ephemeral-volumes).

When running {{agent}} and {{beats}} on GKE Autopilot, storage constraints apply. GKE Autopilot does not allow `hostPath` volumes. By default, the ECK operator uses a `hostPath` volume for the data directory when no alternative volume is configured, whether the workload is deployed as a `Deployment` or a `DaemonSet`. To run successfully, you can use [Kubernetes ephemeral volumes](https://kubernetes.io/docs/concepts/storage/ephemeral-volumes) instead.