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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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13 changes: 13 additions & 0 deletions pkg/types/validation/installconfig.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ import (
"k8s.io/apimachinery/pkg/util/sets"
"k8s.io/apimachinery/pkg/util/validation/field"
utilsnet "k8s.io/utils/net"
"k8s.io/utils/ptr"

configv1 "github.com/openshift/api/config/v1"
"github.com/openshift/api/features"
Expand Down Expand Up @@ -797,6 +798,7 @@ func validateComputeEdge(platform *types.Platform, pName string, fldPath *field.

func validateCompute(platform *types.Platform, control *types.MachinePool, pools []types.MachinePool, fldPath *field.Path) field.ErrorList {
allErrs := field.ErrorList{}
controlReplicas, computeReplicas := int64(0), int64(0)
// Multi Arch is enabled by default for AWS and GCP, these are also the only
// two valid platforms for multi arch installations.
isMultiArchEnabled := platform.AWS != nil || platform.GCP != nil
Expand All @@ -805,6 +807,7 @@ func validateCompute(platform *types.Platform, control *types.MachinePool, pools
poolFldPath := fldPath.Index(i)
switch p.Name {
case types.MachinePoolComputeRoleName:
computeReplicas += ptr.Deref(p.Replicas, 0)
case types.MachinePoolEdgeRoleName:
allErrs = append(allErrs, validateComputeEdge(platform, p.Name, poolFldPath, poolFldPath)...)
default:
Expand All @@ -824,6 +827,16 @@ func validateCompute(platform *types.Platform, control *types.MachinePool, pools
allErrs = append(allErrs, field.Invalid(poolFldPath.Child("fencing"), p.Fencing, "fencing is only valid for control plane"))
}
}

if control != nil {
controlReplicas = ptr.Deref(control.Replicas, 3)
}

// 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) {
Comment on lines +835 to +836
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@tthvo tthvo Nov 5, 2025

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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?

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@tthvo tthvo Nov 5, 2025

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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?

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@zaneb zaneb Nov 7, 2025

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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.

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"))
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@gpei gpei Nov 3, 2025

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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?

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@tthvo tthvo Nov 5, 2025

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+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"))

}

return allErrs
}

Expand Down
85 changes: 80 additions & 5 deletions pkg/types/validation/installconfig_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@ import (
"github.com/stretchr/testify/assert"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/util/validation/field"
"k8s.io/utils/pointer"
utilsslice "k8s.io/utils/strings/slices"

configv1 "github.com/openshift/api/config/v1"
Expand All @@ -31,6 +30,12 @@ import (

const TechPreviewNoUpgrade = "TechPreviewNoUpgrade"

func validControlPlane() *types.MachinePool {
mp := validMachinePool("master")
mp.Replicas = ptr.Int64(3)
return mp
}

func validInstallConfig() *types.InstallConfig {
return &types.InstallConfig{
TypeMeta: metav1.TypeMeta{
Expand All @@ -41,8 +46,8 @@ func validInstallConfig() *types.InstallConfig {
},
BaseDomain: "test-domain",
Networking: validIPv4NetworkingConfig(),
ControlPlane: validMachinePool("master"),
Compute: []types.MachinePool{*validMachinePool("worker")},
ControlPlane: validControlPlane(),
Compute: []types.MachinePool{func() types.MachinePool { p := *validMachinePool("worker"); p.Replicas = ptr.Int64(0); return p }()},
Platform: types.Platform{
AWS: validAWSPlatform(),
},
Expand Down Expand Up @@ -801,7 +806,7 @@ func TestValidateInstallConfig(t *testing.T) {
name: "control plane with 0 replicas",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = pointer.Int64Ptr(0)
c.ControlPlane.Replicas = ptr.Int64(0)
return c
}(),
expectedError: `^controlPlane.replicas: Invalid value: 0: number of control plane replicas must be positive$`,
Expand Down Expand Up @@ -850,7 +855,69 @@ func TestValidateInstallConfig(t *testing.T) {
c.Compute = []types.MachinePool{
func() types.MachinePool {
p := *validMachinePool("worker")
p.Replicas = pointer.Int64Ptr(0)
p.Replicas = ptr.Int64(0)
return p
}(),
}
return c
}(),
},
{
name: "one compute replica, one control plane, AWS",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
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@tthvo tthvo Nov 5, 2025

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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)?

c.Compute = []types.MachinePool{
func() types.MachinePool {
p := *validMachinePool("worker")
p.Replicas = ptr.Int64(1)
return p
}(),
}
return c
}(),
expectedError: `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`,
},
{
name: "one compute replicas, 3 control plane, AWS",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = ptr.Int64(3)
c.Compute = []types.MachinePool{
func() types.MachinePool {
p := *validMachinePool("worker")
p.Replicas = ptr.Int64(1)
return p
}(),
}
return c
}(),
expectedError: `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`,
},
{
name: "one compute replicas, one control plane, None/External",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.Platform = types.Platform{
None: &none.Platform{},
}
c.Compute = []types.MachinePool{
func() types.MachinePool {
p := *validMachinePool("worker")
p.Replicas = ptr.Int64(1)
return p
}(),
}
return c
}(),
},
{
name: "two compute replicas allowed",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.Compute = []types.MachinePool{
func() types.MachinePool {
p := *validMachinePool("worker")
p.Replicas = ptr.Int64(2)
return p
}(),
}
Expand Down Expand Up @@ -910,6 +977,7 @@ func TestValidateInstallConfig(t *testing.T) {
name: "valid baremetal platform",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = ptr.Int64(1)
c.Capabilities = &types.Capabilities{BaselineCapabilitySet: "v4.11"}
c.Capabilities.AdditionalEnabledCapabilities = append(c.Capabilities.AdditionalEnabledCapabilities, configv1.ClusterVersionCapabilityIngress, configv1.ClusterVersionCapabilityCloudCredential, configv1.ClusterVersionCapabilityCloudControllerManager, configv1.ClusterVersionCapabilityOperatorLifecycleManager)
c.Platform = types.Platform{
Expand Down Expand Up @@ -1672,6 +1740,7 @@ func TestValidateInstallConfig(t *testing.T) {
name: "invalidly set cloud credentials mode",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = ptr.Int64(1)
c.Platform = types.Platform{BareMetal: validBareMetalPlatform()}
c.Capabilities = &types.Capabilities{BaselineCapabilitySet: configv1.ClusterVersionCapabilitySetCurrent}
c.CredentialsMode = types.PassthroughCredentialsMode
Expand Down Expand Up @@ -1859,6 +1928,7 @@ func TestValidateInstallConfig(t *testing.T) {
name: "apivip_v4_not_in_machinenetwork_cidr_usermanaged_loadbalancer",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = ptr.Int64(1)
c.FeatureSet = configv1.TechPreviewNoUpgrade
c.Networking.MachineNetwork = []types.MachineNetworkEntry{
{CIDR: *ipnet.MustParseCIDR("10.0.0.0/16")},
Expand Down Expand Up @@ -2160,6 +2230,7 @@ func TestValidateInstallConfig(t *testing.T) {
name: "identical_apivip_ingressvip_usermanaged_loadbalancer",
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.ControlPlane.Replicas = ptr.Int64(1)
c.FeatureSet = configv1.TechPreviewNoUpgrade
c.Platform = types.Platform{
BareMetal: validBareMetalPlatform(),
Expand Down Expand Up @@ -2548,6 +2619,7 @@ func TestValidateInstallConfig(t *testing.T) {
c := validInstallConfig()
c.BareMetal = validBareMetalPlatform()
c.AWS = nil
c.ControlPlane.Replicas = ptr.Int64(1)
c.Capabilities = &types.Capabilities{
BaselineCapabilitySet: configv1.ClusterVersionCapabilitySetCurrent,
}
Expand All @@ -2560,6 +2632,7 @@ func TestValidateInstallConfig(t *testing.T) {
c := validInstallConfig()
c.BareMetal = validBareMetalPlatform()
c.AWS = nil
c.ControlPlane.Replicas = ptr.Int64(1)
c.Capabilities = &types.Capabilities{
BaselineCapabilitySet: configv1.ClusterVersionCapabilitySetNone,
AdditionalEnabledCapabilities: []configv1.ClusterVersionCapability{configv1.ClusterVersionCapabilityBaremetal, configv1.ClusterVersionCapabilityMachineAPI, configv1.ClusterVersionCapabilityIngress},
Expand All @@ -2584,6 +2657,7 @@ func TestValidateInstallConfig(t *testing.T) {
c := validInstallConfig()
c.Platform.AWS = nil
c.Platform.None = &none.Platform{}
c.ControlPlane.Replicas = ptr.Int64(1)
c.Capabilities = &types.Capabilities{
BaselineCapabilitySet: configv1.ClusterVersionCapabilitySetNone,
AdditionalEnabledCapabilities: []configv1.ClusterVersionCapability{configv1.ClusterVersionCapabilityIngress},
Expand All @@ -2596,6 +2670,7 @@ func TestValidateInstallConfig(t *testing.T) {
installConfig: func() *types.InstallConfig {
c := validInstallConfig()
c.Platform.AWS = nil
c.ControlPlane.Replicas = ptr.Int64(1)
c.Platform.BareMetal = validBareMetalPlatform()
c.Capabilities = &types.Capabilities{
BaselineCapabilitySet: configv1.ClusterVersionCapabilitySetNone,
Expand Down