kubernetes-sigs/cluster-api

Topology should validate failureDomain before creating MachineDeployments

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#5,859 opened on Dec 14, 2021

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area/clusterclasshelp wantedkind/featurepriority/important-longtermtriage/accepted

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Description

User Story

As a user, I would like to have validation on failureDomain value selected for my MachineDeployments

Detailed Description

This is a follow up of https://github.com/kubernetes-sigs/cluster-api/pull/5850#discussion_r767892624

https://github.com/kubernetes-sigs/cluster-api/pull/5850 introduced the possibility to spread MachineDeployments across failureDomains, however, on creation it is not possible to validate the selected failureDomain matches one of the available failureDomains, given that they are derived from the InfrastructureCluster after Cluster creation.

So this issue is about discussing options to ensure that a MachineDeployment gets created only if the corresponding failureDomain exists.

Option 1. We should wait to create a MachineDeployment until available failureDomains are reported on the Cluster.Status, providing evidence of this in the TopologyReconciled conditions. If the required failureDomain does not match any available failureDomains, this is a reconcile error.

Option 2. If the available failureDomains are reported on the Cluster.Status, we should validate failureDomain for new MachineDeployments/edited MachineDeployments upfront.

Option 1 and 2 are not exclusive

/kind feature /area topology /milestone v1.1

Contributor guide

Research direction
Investigate the TopologyReconciled conditions and Cluster.Status to detect available failureDomains. Then implement validation that checks selected failureDomain against the available ones before creating or updating MachineDeployments. Consider both options: deferring creation until failureDomains are reported (Option 1) and upfront validation when available (Option 2).
Tech stack
go
Domain
backendapi
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
GoKubernetesCluster API
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
60