External etcd lifecycle support

[g-gaston]

User Story

As an operator, I would like to be able to manage the lifecycle of external etcd clusters in the same way I do for control planes, using CAPI primitives.

Detailed Description

Cluster API supports the use of an external etcd cluster, by allowing users to provide their external etcd cluster's endpoints.
So it would be good to add support for provisioning the etcd cluster too, so the user can have a single workflow for full management of a cluster using the external etcd topology. The user can offload the responsibility of managing an external etcd cluster to CAPI.

Anything else you would like to add:

Why unstacked etcd is valuable:

• External etcd topology decouples the control plane and etcd member. So if a control plane-only node fails, or if there's a memory leak in a component like kube-apiserver, it won't directly impact an etcd member.

• Etcd is resource intensive, so it is safer to have dedicated nodes for etcd, it could use more disk space, higher bandwidth. Having a separate etcd cluster for these reasons could ensure a more resilient HA setup.

Original proposal #4659

/kind feature

[g-gaston]

@fabriziopandini, as promised :)
I'll follow up with a new PR

[fabriziopandini]

/triage accepted
/remove-kind feature
/kind proposal

[k8s-triage-robot]

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• After 90d of inactivity, lifecycle/stale is applied
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• After 30d of inactivity since lifecycle/rotten was applied, the issue is closed

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/lifecycle stale

[nanorobocop]

How about just separating controlplane and etcd node roles?
Means provision etcd as static pods in cluster, just on dedicated for etcd nodes.
The main goal would be same - dedicated nodes for etcd (but also with kubelet).

If add 'etcd' node role, that would also help to transform cluster from one type to another.
Initially cluster could be with joined controlplane+etcd roles.
And could be transformed to separated controlplane and etcd nodes, just by changing node roles.

[vincepri]

/lifecycle frozen

[fabriziopandini]

/triage backlog

[k8s-ci-robot]

@fabriziopandini: The label(s) triage/backlog cannot be applied, because the repository doesn't have them.

In response to this:

/triage backlog

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[fabriziopandini]

/priority backlog

[fabriziopandini]

The Cluster API project currently lacks enough active contributors to adequately respond to all issues and PRs.

I don't see activity or progress around this topic, we might eventually reconsider if conditions change

/close

[k8s-ci-robot]

@fabriziopandini: Closing this issue.

In response to this:

The Cluster API project currently lacks enough active contributors to adequately respond to all issues and PRs.

I don't see activity or progress around this topic, we might eventually reconsider if conditions change

/close

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.