Add support for node pool placement group config

[dominic-p]

What type of PR is this?

/kind feature

What this PR does / why we need it:

This PR adds support for specifying a placement group for a node pool using the HCLOUD_CLUSTER_CONFIG JSON. This is a nice feature to have because it allows you to spread a node pool's VMs over different physical hardware, increasing the overall resilience of the pool.

Which issue(s) this PR fixes:

Fixes #5919

Special notes for your reviewer:

This is the first go code that I have written, so I apologize if it's a total mess. Also, I'm not sure how to setup a dev/testing environment for this project, so I was not able to actually run this code to test it.

Does this PR introduce a user-facing change?

Add support for specifying node pool placement groups when using HCLOUD_CLUSTER_CONFIG

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

To specify a placement group, use JSON like this:

{
  "nodeConfigs": {
    "pool-1": {
      "placementGroup": "name or ID here"
    }
}

[k8s-ci-robot]

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[k8s-ci-robot]

Hi @dominic-p. Thanks for your PR.

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[dominic-p]

Friendly bump. Is there anything I can do to polish this PR or help with the review process?

[lukasmetzner]

Hey,

thanks for opening the PR and sorry for the long wait ^^ It mostly works, a few go syntax issues and you also have to add the placement groups to the server creation request:

hetzner_node_group.go:449

opts := hcloud.ServerCreateOpts{
    ...
    PlacementGroup: n.placementGroup,
}

[dominic-p]

Thank you so much for the review! I believe I have implemented all of your suggested changes. Let me know what you think.

I'm seeing a ton of errors in the CI tests, but they don't seem to be relevant to this PR. It's hard for me to say though.

[apricote]

One of the files is not properly formatted, that causes the CI failure in test-and-verify. You can fix it by following the CI output:

Please run hack/update-gofmt.sh to fix the following files:
./cluster-autoscaler/cloudprovider/hetzner/hetzner_cloud_provider.go

(And yes, most of the issues in the output are not relevant to this PR and the important line is very easy to miss)

[dominic-p]

Ok, it looks like the tests are passing now. If we do wind up with a placement group that would be too large, the error message is maybe a little less readable now (it will reference placement group IDs instead of names). But, this seemed like the cleanest way to solve the problems.

Let me know if you would prefer a different approach.

[apricote]

/approve

Thank you very much @dominic-p!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: apricote, dominic-p

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Needs approval from an approver in each of these files:

• cluster-autoscaler/cloudprovider/hetzner/OWNERS [apricote]

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[apricote]

/lgtm

[dominic-p]

You are very welcome, and thank you for being so patient with me as I tried to learn go for this PR. :)