Improve utilities for gwctl describe and add more info to gateway descriptions

[gauravkghildiyal]

What this PR does / why we need it:

• Add helpers to print gwctl describe views and Tables
• Add more information when describing Gateways (like attached routes)
• Discover events associated with Gateways and output them when describing Gateways.

Example:

❯ gwctl describe gateways
Name: demo-gateway-1
Namespace: default
Labels: null
Annotations:
  kubectl.kubernetes.io/last-applied-configuration: |
    {"apiVersion":"gateway.networking.k8s.io/v1beta1","kind":"Gateway","metadata":{"annotations":{},"name":"demo-gateway-1","namespace":"default"},"spec":{"gatewayClassName":"foo-com-external-gateway-class","listeners":[{"name":"http","port":80,"protocol":"HTTP"}]}}
APIVersion: gateway.networking.k8s.io/v1
Kind: Gateway
Metadata:
  creationTimestamp: "2024-04-03T04:27:12Z"
  generation: 1
  managedFields:
  - apiVersion: gateway.networking.k8s.io/v1beta1
    fieldsType: FieldsV1
    fieldsV1:
      f:metadata:
        f:annotations:
          .: {}
          f:kubectl.kubernetes.io/last-applied-configuration: {}
      f:spec:
        .: {}
        f:gatewayClassName: {}
        f:listeners:
          .: {}
          k:{"name":"http"}:
            .: {}
            f:allowedRoutes:
              .: {}
              f:namespaces:
                .: {}
                f:from: {}
            f:name: {}
            f:port: {}
            f:protocol: {}
    manager: kubectl-client-side-apply
    operation: Update
    time: "2024-04-03T04:27:12Z"
  resourceVersion: "2531077"
  uid: 034c4490-6b0d-41f0-8d90-3948dbae4b6c
Spec:
  gatewayClassName: foo-com-external-gateway-class
  listeners:
  - allowedRoutes:
      namespaces:
        from: Same
    name: http
    port: 80
    protocol: HTTP
Status:
  conditions:
  - lastTransitionTime: "1970-01-01T00:00:00Z"
    message: Waiting for controller
    reason: Pending
    status: Unknown
    type: Accepted
  - lastTransitionTime: "1970-01-01T00:00:00Z"
    message: Waiting for controller
    reason: Pending
    status: Unknown
    type: Programmed
AttachedRoutes:
  Kind       Name
  ----       ----
  HTTPRoute  default/demo-httproute-1
  HTTPRoute  default/demo-httproute-2
  HTTPRoute  default/demo-httproute-3
  HTTPRoute  ns2/demo-httproute-4
DirectlyAttachedPolicies:
  Type                       Name
  ----                       ----
  HealthCheckPolicy.foo.com  default/demo-health-check-1
  RetryOnPolicy.foo.com      default/demo-retry-policy-1
EffectivePolicies:
  HealthCheckPolicy.foo.com:
    sampleParentField:
      sampleField: hello
  RetryOnPolicy.foo.com:
    sampleParentField:
      sampleField: namaste
  TimeoutPolicy.bar.com:
    timeout1: parent
    timeout2: child
    timeout3: parent
    timeout4: child
Events:
  Type     Reason  Age  From                   Message
  ----     ------  ---  ----                   -------
  Warning  SYNC    12h  my-gateway-controller  Some message here

Notes for reviewer:
Reviewing individual commits in order might be easier

Which issue(s) this PR fixes:

Fixes #

Does this PR introduce a user-facing change?:

NONE

[gauravkghildiyal]

/cc @mlavacca

[mlavacca]

Apart from a very minor nit in a comment, it looks good to me. I unfortunately do not feel 100% confident in reviewing this code as I lack some context. I'd love to hear some other opinions as well here :)

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: gauravkghildiyal, mlavacca

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[robscott]

Thanks for all the work on this @gauravkghildiyal!

[robscott]

Wouldn't you also need group here? Otherwise you might end up with some unexpected data related to other Gateway resources like Istio Gateways.

[gauravkghildiyal]

Great catch!

Indeed we would need something of that sorts...the right choice seems to be the UID (which is what kubectl uses as well). Reason being, there's no neat way to use the API to only query the APIGroup (and not the APIVersion) which would have caused problems with gatewayv1 vs gatewayv1beta1. Anyways, UID doesn't cause any such issues.

Thanks a lot for the great find

[robscott]

This seems like it would get painful, would it be better to require that Gateway controllers set specific labels on Events they're publishing?

[gauravkghildiyal]

Anything specific in your mind about the pain points? I guess some should get addressed as described in the other comment https://github.com/kubernetes-sigs/gateway-api/pull/2999/files#r1585597856 and we may not need it for the time being.

[robscott]

If I'm understanding correctly, this is more for just test mocks or something right? It looks like you're using this to list events. Maybe adjust the description to note that this is the best way to be able to list events that involve a specific resource?

[gauravkghildiyal]

You are absolutely right. Yes the comment could use some improvement, thanks for the suggestion. Hope it's somewhat more meaningful now.

[robscott]

Thanks @gauravkghildiyal!

/lgtm