Add proper validation for nodepool name

[tapojit047]

 
What type of PR is this?
/kind bug

What this PR does / why we need it:

1. According to Azure Docs, these are the nodepool naming restrictions:
       - The name of a node pool may only contain lowercase alphanumeric characters and must begin with a lowercase letter.
       - For Linux node pools, the length must be between 1-12 characters.

But the nodepool name is not validated properly (according to these restrictions). Proper validation following these restrictions in the azuremanagedmachinepool_webhook.go is added.

2. If the name of the nodepool i.e. spec.name field is not specified in the YAML of AzureManagedMachinePool, then the default name is set to the metadata.name. Take a look here. So metadata.name is validated when spec.name is not set.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #3968

Special notes for your reviewer:

• cherry-pick candidate

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Add proper validation for nodepool name

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: tapojit047 / name: Tapajit Chandra Paul (66860ab)

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[k8s-ci-robot]

Hi @tapojit047. Thanks for your PR.

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[CecileRobertMichon]

/ok-to-test

[tapojit047]

/test pull-cluster-api-provider-azure-e2e-aks

[jackfrancis]

Why do we want to truncate the name from MachinePool to 6 chars and then add 6 chars of random characters?

Wouldn't this be sufficient?:

• remove/replace invalid characters
• truncate at the maximum allowed character limit (12)

[tamalsaha]

We would like to avoid naming conflict created from different CAPZ cluster. So, we want to add a random part to the pool name that is passed to Azure.

[jackfrancis]

Thanks for the clarification.

So is the scenario that we might run multiple clusters w/ a common MachinePool naming convention. E.g.:

• cluster1
  • pool1
  • pool2
  • pool3
• cluster2
  • pool1
  • pool2
  • pool3

And you want to have CAPZ ensure that cluster1 and cluster2 don't produce identically named pool names?

[tamalsaha]

Yes. We want to avoid naming conflict.

Also, adding a random part to will not affect ux, since user don't really have to interact with this directly unless they are doing something from the Azure portal.

[jackfrancis]

Thanks again.

So, my initial response to this is that is that this type of enforcement should not be the responsibility of CAPZ. There could be other environments with the exact opposite requirements (require identical pool names across common cluster ecosystems).

Could you enforce this pool naming requirement in your cluster creation CI so that you're fully in control of these requirements?

cc @nojnhuh @CecileRobertMichon

[nojnhuh]

How about validating the AzureManagedMachinePool metadata name according to the Azure pool name rules if and only if the spec.Name field is not explicitly set? And if the spec.Name field is set, we should validate the spec.Name.

Since we already default spec.name to metadata.name when not set, do we only need to validate spec.name?

[CecileRobertMichon]

do we only need to validate spec.name

That would be equivalent, only reason I can think of for doing both is that it might be more user friendly to validate the thing the user is actually setting (otherwise I could see users getting confused with "why am I getting a validation error for something I didn't set"). That's an implementation detail though.

[tamalsaha]

There is no Azure requirement that a pool name must be unique (it should only be unique within a cluster).

I did not realise that. Thanks for the info.

[jackfrancis]

Do we want to convert this into a new PR that validates the AKS 12 character limit, or simply close this PR?

[tapojit047]

Converted it into a validation for the nodepool name PR. @jackfrancis

[codecov]

Codecov Report

Attention: 15 lines in your changes are missing coverage. Please review.

Comparison is base (b195e9a) 56.57% compared to head (66860ab) 56.56%.
Report is 50 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3974      +/-   ##
==========================================
- Coverage   56.57%   56.56%   -0.01%     
==========================================
  Files         187      187              
  Lines       19130    19168      +38     
==========================================
+ Hits        10823    10843      +20     
- Misses       7676     7691      +15     
- Partials      631      634       +3     

Files	Coverage Δ
api/v1beta1/azuremanagedmachinepool_webhook.go	81.42% <64.28%> (-2.87%)	⬇️

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[CecileRobertMichon]

/lgtm
/assign @jackfrancis @nojnhuh

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 60a6bfcab36e64d86d32c985b90b9bed05bc5e6e

[nojnhuh]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: nojnhuh

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