Support showing MachineHealthChecks in `clusterctl describe cluster` output

[ykakarap]

User Story

As a user I would like to be able see MachineHealthChecks acting on a cluster in the at-a-glance view generated by clusterctl describe cluster.

Detailed Description

Currently MHCs are not part of the clusterctl describe cluster output. Since MHCs can be uniquely linked to a specific cluster using MachineHealthCheck.Spec.ClusterName it would be nice to also see them in the output.

Anything else you would like to add:

They can be disabled by default and can sit behind a flag like --show-machinehealthchecks, similar to the other flags we currently have: --show-templates, --show-resourcesets, etc.

/kind feature /area clusterctl

[fabriziopandini]

/triage accepted

it makes sense given that we are extending to all the objects in a cluster, but at the same time I'm not really sure what is the best way to represent them given the mechanism they are using to target machines

[ykakarap]

I guess this can be broken down into 2 things:

1. Listing the MachineHealthChecks that are linked to a cluster in clusterctl describe
2. Showing which MHCs are acting on which Machines

These things can probably be address in 2 steps. The first one is probably straight forward to implement with how clusterctl describe works right now. For the second one, it will need more though on a good UX to show that information.

I think we can do 1 now and implement 2 later once we have a better idea on the UX.

[sbueringer]

+1 not sure if there's a good way to do 2. considering that MHC (as far as I know) could apply to Machines managed by different resources (KCP,MD)

[fabriziopandini]

/help

[k8s-ci-robot]

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[rajaSahil]

Hey @ykakarap, I would like to work on this.

[ykakarap]

@rajaSahil Great! Feel free to assign it to yourself.

[rajaSahil]

Sure. Thank you! /assign

[oscr]

Have you had any time to work on this @rajaSahil?

[fabriziopandini]

/unassign@rajaSahil

Wondering if what we need is clusterctl describe mhc, we rally neead to figure out what we want to achieve here given the relation betwen [edited]~~crs and clusters is 1:n~~ MHC and machines is 1:n

[oscr]

1. Listing the MachineHealthChecks that are linked to a cluster in clusterctl describe

If everyone agrees 1 is a good feature I would be willing to implement this.

[ykakarap]

/unassign@rajaSahil

Wondering if what we need is clusterctl describe mhc, we rally neead to figure out what we want to achieve here given the relation betwen crs and clusters is 1:n

MHC to clusters is 1:1 right? MHC is uniquely matched to a Cluster using mhc.spec.clusterName. I guess usecase 1

1. Listing the MachineHealthChecks that are linked to a cluster in clusterctl describe Is still a useful thing to have in the clusterctl describe output.

[sbueringer]

MHC to clusters is 1:1 right?

Yes a MHC always belongs to a specific cluster, while a cluster can have multiple MHCs (which results in a 1:n relationship). So just listing all MHC's belonging to a cluster would be possible.

@fabriziopandini did you simply mix it up with ClusterResourceSet or where you looking for how we could map MHC's in the output to Control plane / MachineDeployments / MachineSets / Machines?

[fabriziopandini]

yeah sorry if I wasn't clear and a little bit imprecise, edited.

What I what thinking is a two-step process:

1. use clusterctl describe cluster foo --show-mhc to chek the list of mhc existing in a cluster (no further details provided)
2. use clusterctl describe mhc foo-mhc1 to get a new view showing the machines targeted by this mhc instance, and might be also their health instead of the ready condition

but we can start from 1 for now

[oscr]

Thanks everyone for the clarifications! I'll give it a try during the weekend.

/assign

[oscr]

I would like to ask for some advice how to look up the mhc(s). Would a viable option be via the management cluster client to use tree.Discovery()?

[killianmuldoon]

That sounds like the right way to approach this - i.e. insert a new getMachineHealthChecksForCluster somewhere in this function: https://github.com/kubernetes-sigs/cluster-api/blob/f2ba999757aa76b446943a9ffea14ecf8c7523e8/cmd/clusterctl/client/tree/discovery.go#L65

[k8s-triage-robot]

This issue has not been updated in over 1 year, and should be re-triaged.

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/remove-triage accepted

[fabriziopandini]

/triage accepted /priority backlog