Add reserved pid settings migration

[koooosh]

Issue number:

Related to: #3788

Description of changes:

Add migration for pid setting under kube-reserved and system-reserved settings:

• feat: update k8s kube-reserved and system-reserved settings to specify pid  bottlerocket-settings-sdk#98
• kubernetes: add pid resource to kubeReserved setting bottlerocket-core-kit#646

Testing done:

Migration testing:

• Pre-upgrade (expected failure)

apiclient set -j '{
 "settings": {
    "kubernetes": {
      "kube-reserved": {
        "pid": "9999",
        "cpu": "10m",
        "ephemeral-storage": "1Gi", 
        "memory": "100Mi"
      },
      "system-reserved": {
        "pid": "1000",
        "cpu": "10m",
        "ephemeral-storage": "1Gi", 
        "memory": "100Mi"
      }
    }
  }
}'

=> Failed to change settings: Failed PATCH request to '/settings?tx=apiclient-set-tK69YYxBmTQgmkyl': Status 400 when PATCHing /settings?tx=apiclient-set-tK69YYxBmTQgmkyl: Json deserialize error: Unable to deserialize into KubernetesReservedResourceKey: Invalid input for field Reserved sources key: unknown variant `pid`, expected one of `cpu`, `memory`, `ephemeral-storage` at line 1 column 37

• Upgrade

[ssm-user@control]$ apiclient get settings.kubernetes.kube-reserved
{
  "settings": {
    "kubernetes": {
      "kube-reserved": {
        "cpu": "10m",
        "ephemeral-storage": "1Gi",
        "memory": "100Mi",
        "pid": "9999"
      }
    }
  }
}
[ssm-user@control]$ apiclient get settings.kubernetes.system-reserved
{
  "settings": {
    "kubernetes": {
      "system-reserved": {
        "cpu": "10m",
        "ephemeral-storage": "1Gi",
        "memory": "100Mi",
        "pid": "1000"
      }
    }
  }
}
 
=> See the following configs in /etc/kubernetes/kubelet/config where pid is added
kubeReserved:
  cpu: "10m"
  memory: "100Mi"
  ephemeral-storage: "1Gi"
  pid: "9999"
systemReserved:
  cpu: "10m"
  ephemeral-storage: "1Gi"
  memory: "100Mi"
  pid: "1000"

• Downgrade

[ssm-user@control]$ apiclient get settings.kubernetes.system-reserved
{
  "settings": {
    "kubernetes": {
      "system-reserved": {
        "cpu": "10m",
        "ephemeral-storage": "1Gi",
        "memory": "100Mi"
      }
    }
  }
}
[ssm-user@control]$ apiclient get settings.kubernetes.kube-reserved
{
  "settings": {
    "kubernetes": {
      "kube-reserved": {
        "cpu": "10m",
        "ephemeral-storage": "1Gi",
        "memory": "100Mi"
      }
    }
  }
}

=> See the following configs in /etc/kubernetes/kubelet/config where pid is removed
kubeReserved:
  cpu: "10m"
  memory: "100Mi"
  ephemeral-storage: "1Gi"
systemReserved:
  cpu: "10m"
  ephemeral-storage: "1Gi"
  memory: "100Mi"

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[koooosh]

^ Force push fixes a clippy error

[KCSesh]

Can we add context (maybe to the comment) why we are using AddPrefixesMigration vs the usual AddSettingsMigration for a setting.

I know it was called out here:
bottlerocket-os/bottlerocket-settings-sdk#98 (review)

But I am curious on the behavior.

[koooosh]

Thanks for the callout! I reran migration testing using AddSettingsMigration instead and it worked -- the results were the same.

Although AddPrefixesMigration technically works, I believe AddSettingsMigration is the correct helper here since the pid setting is supposed to be set to a single value (so not a prefix for other settings). If pid had it's own map, then AddPrefixesMigration would be the right choice. I've fixed this in the latest push.

[koooosh]

^ Force push replaces AddPrefixesMigration helper to AddSettingsMigration