OCPBUGS-56954: Disallow 1 worker node with exception #10042

sadasu · 2025-10-29T18:35:51Z

1 worker node is allowed only when SNO is configured on platforms None or External. Add validation disallowing 1 worker node for other scenarios.

openshift-ci-robot · 2025-10-29T18:35:57Z

@sadasu: This pull request references Jira Issue OCPBUGS-56954, which is invalid:

expected the bug to target the "4.21.0" version, but no target version was set

Comment /jira refresh to re-evaluate validity if changes to the Jira bug are made, or edit the title of this pull request to link to a different bug.

The bug has been updated to refer to the pull request using the external bug tracker.

In response to this:

1 worker node is allowed only when SNO is configured on platforms None or External. Add validation disallowing 1 worker node for other scenarios.

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openshift-ci · 2025-10-29T18:36:15Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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sadasu · 2025-10-29T18:41:26Z

/jira refresh

openshift-ci-robot · 2025-10-29T18:41:33Z

@sadasu: This pull request references Jira Issue OCPBUGS-56954, which is valid. The bug has been moved to the POST state.

3 validation(s) were run on this bug

bug is open, matching expected state (open)
bug target version (4.21.0) matches configured target version for branch (4.21.0)
bug is in the state ASSIGNED, which is one of the valid states (NEW, ASSIGNED, POST)

Requesting review from QA contact:
/cc @gpei

In response to this:

/jira refresh

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1 worker node is allowed only when SNO is configured on platforms None or External. Add validation disallowing 1 worker node for other scenarios.

openshift-ci · 2025-10-30T19:43:47Z

@sadasu: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/artifacts-images	`9dbd36b`	link	true	`/test artifacts-images`
ci/prow/images	`9dbd36b`	link	true	`/test images`
ci/prow/e2e-aws-ovn	`9dbd36b`	link	true	`/test e2e-aws-ovn`
ci/prow/okd-scos-e2e-aws-ovn	`9dbd36b`	link	false	`/test okd-scos-e2e-aws-ovn`

Full PR test history. Your PR dashboard.

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-sigs/prow repository. I understand the commands that are listed here.

sadasu · 2025-10-31T17:19:17Z

/payload ?

openshift-ci · 2025-10-31T17:19:19Z

@sadasu: it appears that you have attempted to use some version of the payload command, but your comment was incorrectly formatted and cannot be acted upon. See the docs for usage info.

gpei · 2025-11-03T05:09:13Z

pkg/types/validation/installconfig.go

+
+	// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External
+	if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil || platform.External != nil) {
+		allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))


Should we say

Suggested change

allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))

allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or at least 2 workers for multi-node clusters"))

in this error msg?

+1 as users might mistake it to exactly 2. We should probably use the correct field path:

Suggested change

allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))

allErrs = append(allErrs, field.Invalid(fldPath.Child("replicas"), computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or at least 2 workers for multi-node clusters"))

gpei · 2025-11-03T06:52:15Z

Performed pre-merge testing with this PR, and the installer correctly handles the various scenarios where 1 worker is set in the install-config.

Installer blocks 1 worker + 3 control plane on AWS with error message

ERROR failed to fetch Master Machines: failed to load asset "Install Config": failed to create install config: invalid "install-config.yaml" file: compute: Invalid value: 1: exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters

Installer allows 1 worker + 1 control plane on Azure
Installer allows compact cluster, with 0 worker + 3 control plane
Installer allows SNO cluster, with 0 worker + 1 control plane
Installer allows 1 worker + 3 control plane on none/external platform

tthvo · 2025-11-05T00:46:52Z

pkg/types/validation/installconfig.go

+
+	// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External
+	if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil || platform.External != nil) {
+		allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))


+1 as users might mistake it to exactly 2. We should probably use the correct field path:

Suggested change

allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))

allErrs = append(allErrs, field.Invalid(fldPath.Child("replicas"), computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or at least 2 workers for multi-node clusters"))

tthvo · 2025-11-05T01:04:11Z

pkg/types/validation/installconfig.go

+	// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External
+	if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil || platform.External != nil) {


Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External

Regarding the comment, it hints that only SNO and platform none/external is allowed. But from #10042 (comment) and official doc, either SNO or none/external platform is allowed, which also matches the current code implementation.

I guess the comment is incorrect?

Suggested change

// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External

if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil || platform.External != nil) {

// Validate that exactly 1 worker node is allowed only in either the following scenarios:

// 1. A single control plane node (SNO) is provisioned.

// 2. Platforms are None or External.

if computeReplicas == 1 {

isSNO := controlReplicas == 1

isAllowedPlatform := platform.None != nil || platform.External != nil

if !isSNO && !isAllowedPlatform {

nit: It seems a bit more verbose, but improves readability? WDYT?

1+1 is actually not a valid topology on day 1. Assisted is not capable of creating an SNO with worker nodes.
But 3+1 is actually a valid topology, the bug report notwithstanding.

tthvo · 2025-11-05T01:19:37Z

pkg/types/validation/installconfig_test.go

+		{
+			name: "one compute replica, one control plane, AWS",
+			installConfig: func() *types.InstallConfig {
+				c := validInstallConfig()


Suggested change

c := validInstallConfig()

c := validInstallConfig()

c.ControlPlane.Replicas = ptr.Int64(1)

The default now is 3 right? As in line 33-37. So we need to set it 1, which makes this case valid (i.e. expectedError to be nil)?

openshift-ci-robot added jira/valid-reference Indicates that this PR references a valid Jira ticket of any type. jira/invalid-bug Indicates that a referenced Jira bug is invalid for the branch this PR is targeting. labels Oct 29, 2025

openshift-ci bot requested review from jhixson74 and rna-afk October 29, 2025 18:36

openshift-ci-robot added the jira/valid-bug Indicates that a referenced Jira bug is valid for the branch this PR is targeting. label Oct 29, 2025

openshift-ci-robot removed the jira/invalid-bug Indicates that a referenced Jira bug is invalid for the branch this PR is targeting. label Oct 29, 2025

openshift-ci bot requested a review from gpei October 29, 2025 18:41

sadasu force-pushed the disallow-1-worker branch 3 times, most recently from 6ecd1b4 to 569a247 Compare October 30, 2025 14:59

Disallow 1 worker node with exception

9dbd36b

1 worker node is allowed only when SNO is configured on platforms None or External. Add validation disallowing 1 worker node for other scenarios.

sadasu force-pushed the disallow-1-worker branch from 569a247 to 9dbd36b Compare October 30, 2025 15:22

gpei reviewed Nov 3, 2025

View reviewed changes

tthvo reviewed Nov 5, 2025

View reviewed changes

	allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or 2 workers for multi-node clusters"))
	allErrs = append(allErrs, field.Invalid(fldPath, computeReplicas, "exactly 1 worker node is not allowed for this platform and configuration. Use 0 workers for single-node clusters or at least 2 workers for multi-node clusters"))

		// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External
		if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil \|\| platform.External != nil) {

-	// Validate that exactly 1 worker node is allowed only when a single control plane node is provisioned on platforms None or External
-	if computeReplicas == 1 && controlReplicas != 1 && !(platform.None != nil || platform.External != nil) {
+    // Validate that exactly 1 worker node is allowed only in either the following scenarios:
+	// 1. A single control plane node (SNO) is provisioned.
+	// 2. Platforms are None or External.
+	if computeReplicas == 1 {
+		isSNO := controlReplicas == 1
+		isAllowedPlatform := platform.None != nil || platform.External != nil
+		if !isSNO && !isAllowedPlatform {

	c := validInstallConfig()
	c := validInstallConfig()
	c.ControlPlane.Replicas = ptr.Int64(1)

OCPBUGS-56954: Disallow 1 worker node with exception #10042

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OCPBUGS-56954: Disallow 1 worker node with exception #10042

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