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Merged
knative-prow merged 1 commit into from
May 12, 2026
Merged

feat: add support for generic ephemeral volumes #16590

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3 changes: 3 additions & 0 deletions cmd/schema-tweak/overrides.go
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Expand Up @@ -254,6 +254,9 @@ func revSpecOverrides(prefixPath string) []entry {
}, {
name: "image",
flag: config.FeaturePodSpecVolumesImage,
}, {
name: "ephemeral",
flag: config.FeaturePodSpecVolumesEphemeral,
}},
}, {
path: "volumes.secret",
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5 changes: 5 additions & 0 deletions config/core/300-resources/configuration.yaml
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Expand Up @@ -1180,6 +1180,11 @@ spec:
This is accessible behind a feature flag - kubernetes.podspec-volumes-emptydir
type: object
x-kubernetes-preserve-unknown-fields: true
ephemeral:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-ephemeral
type: object
x-kubernetes-preserve-unknown-fields: true
Comment on lines +1183 to +1187
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@linkvt linkvt May 8, 2026 •
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I just learned that we should extend the following code to get these changes instead of manually applying them:

serving/cmd/schema-tweak/overrides.go

Lines 251 to 257 in fb213e0

}, {
name: "csi",
flag: config.FeaturePodSpecVolumesCSI,
}, {
name: "image",
flag: config.FeaturePodSpecVolumesImage,
}},

(CI failed for this reason)

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@jbunting jbunting May 8, 2026

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Ah, I missed that. I'll get that updated.

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@jbunting jbunting May 8, 2026

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I've added this and the related test is passing now.

hostPath:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-hostpath
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5 changes: 5 additions & 0 deletions config/core/300-resources/revision.yaml
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Expand Up @@ -1156,6 +1156,11 @@ spec:
This is accessible behind a feature flag - kubernetes.podspec-volumes-emptydir
type: object
x-kubernetes-preserve-unknown-fields: true
ephemeral:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-ephemeral
type: object
x-kubernetes-preserve-unknown-fields: true
hostPath:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-hostpath
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5 changes: 5 additions & 0 deletions config/core/300-resources/service.yaml
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Expand Up @@ -1198,6 +1198,11 @@ spec:
This is accessible behind a feature flag - kubernetes.podspec-volumes-emptydir
type: object
x-kubernetes-preserve-unknown-fields: true
ephemeral:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-ephemeral
type: object
x-kubernetes-preserve-unknown-fields: true
hostPath:
description: |-
This is accessible behind a feature flag - kubernetes.podspec-volumes-hostpath
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8 changes: 7 additions & 1 deletion config/core/configmaps/features.yaml
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Expand Up @@ -22,7 +22,7 @@ metadata:
app.kubernetes.io/component: controller
app.kubernetes.io/version: devel
annotations:
knative.dev/example-checksum: "bee75b26"
knative.dev/example-checksum: "424df6ce"
data:
_example: |-
################################
Expand Down Expand Up @@ -207,6 +207,12 @@ data:
# 2. Disabled: disabling HostPath volume support
kubernetes.podspec-volumes-hostpath: "disabled"

# Controls whether volume support for generic ephemeral volumes is enabled or not.
# See https://kubernetes.io/docs/concepts/storage/ephemeral-volumes/#generic-ephemeral-volumes
# 1. Enabled: enabling generic ephemeral volume support
# 2. Disabled: disabling generic ephemeral volume support
kubernetes.podspec-volumes-ephemeral: "disabled"

# Controls whether volume support for CSI is enabled or not.
# 1. Enabled: enabling CSI volume support
# 2. Disabled: disabling CSI volume support
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4 changes: 4 additions & 0 deletions pkg/apis/config/features.go
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Expand Up @@ -76,6 +76,7 @@ const (
FeaturePodSpecShareProcessNamespace = "kubernetes.podspec-shareprocessnamespace"
FeaturePodSpecTolerations = "kubernetes.podspec-tolerations"
FeaturePodSpecTopologySpreadConstraints = "kubernetes.podspec-topologyspreadconstraints"
FeaturePodSpecVolumesEphemeral = "kubernetes.podspec-volumes-ephemeral"
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@linkvt linkvt May 8, 2026

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We should probably also add a test for this new feature as there are tests in features_test.go for the other Volumes

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@jbunting jbunting May 8, 2026

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Good point, I'll add that.

FeaturePodSpecVolumesImage = "kubernetes.podspec-volumes-image"
)

Expand All @@ -102,6 +103,7 @@ func defaultFeaturesConfig() *Features {
PodSpecVolumesHostPath: Disabled,
PodSpecVolumesMountPropagation: Disabled,
PodSpecVolumesCSI: Disabled,
PodSpecVolumesEphemeral: Disabled,
PodSpecVolumesImage: Disabled,
PodSpecPersistentVolumeClaim: Disabled,
PodSpecPersistentVolumeWrite: Disabled,
Expand Down Expand Up @@ -141,6 +143,7 @@ func NewFeaturesConfigFromMap(data map[string]string) (*Features, error) {
asFlag(FeaturePodSpecHostPID, &nc.PodSpecHostPID),
asFlag(FeaturePodSpecHostPath, &nc.PodSpecVolumesHostPath),
asFlag(FeaturePodSpecVolumesCSI, &nc.PodSpecVolumesCSI),
asFlag(FeaturePodSpecVolumesEphemeral, &nc.PodSpecVolumesEphemeral),
asFlag(FeaturePodSpecVolumesImage, &nc.PodSpecVolumesImage),
asFlag(FeaturePodSpecInitContainers, &nc.PodSpecInitContainers),
asFlag(FeaturePodSpecVolumesMountPropagation, &nc.PodSpecVolumesMountPropagation),
Expand Down Expand Up @@ -187,6 +190,7 @@ type Features struct {
PodSpecVolumesHostPath Flag
PodSpecVolumesMountPropagation Flag
PodSpecVolumesCSI Flag
PodSpecVolumesEphemeral Flag
PodSpecVolumesImage Flag
PodSpecInitContainers Flag
PodSpecPersistentVolumeClaim Flag
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18 changes: 18 additions & 0 deletions pkg/apis/config/features_test.go
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Expand Up @@ -480,6 +480,24 @@ func TestFeaturesConfiguration(t *testing.T) {
data: map[string]string{
"kubernetes.podspec-volumes-csi": "Enabled",
},
}, {
name: "kubernetes.podspec-volumes-ephemeral Disabled",
wantErr: false,
wantFeatures: defaultWith(&Features{
PodSpecVolumesEphemeral: Disabled,
}),
data: map[string]string{
"kubernetes.podspec-volumes-ephemeral": "Disabled",
},
}, {
name: "kubernetes.podspec-volumes-ephemeral Enabled",
wantErr: false,
wantFeatures: defaultWith(&Features{
PodSpecVolumesEphemeral: Enabled,
}),
data: map[string]string{
"kubernetes.podspec-volumes-ephemeral": "Enabled",
},
}, {
name: "kubernetes.podspec-persistent-volume-claim Disabled",
wantErr: false,
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4 changes: 4 additions & 0 deletions pkg/apis/serving/fieldmask.go
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Expand Up @@ -76,6 +76,10 @@ func VolumeSourceMask(ctx context.Context, in *corev1.VolumeSource) *corev1.Volu
out.CSI = in.CSI
}

if cfg.Features.PodSpecVolumesEphemeral != config.Disabled {
out.Ephemeral = in.Ephemeral
}

if cfg.Features.PodSpecVolumesImage != config.Disabled {
out.Image = in.Image
}
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13 changes: 12 additions & 1 deletion pkg/apis/serving/k8s_validation.go
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Expand Up @@ -138,6 +138,10 @@ func validateVolume(ctx context.Context, volume corev1.Volume) *apis.FieldError
errs = errs.Also(&apis.FieldError{Message: fmt.Sprintf("CSI volume support is disabled, "+
"but found CSI volume %s", volume.Name)})
}
if volume.Ephemeral != nil && features.PodSpecVolumesEphemeral != config.Enabled {
errs = errs.Also(&apis.FieldError{Message: fmt.Sprintf("Ephemeral volume support is disabled, "+
"but found Ephemeral volume %s", volume.Name)})
}
errs = errs.Also(apis.CheckDisallowedFields(volume, *VolumeMask(ctx, &volume)))
if volume.Name == "" {
errs = apis.ErrMissingField("name")
Expand Down Expand Up @@ -182,6 +186,10 @@ func validateVolume(ctx context.Context, volume corev1.Volume) *apis.FieldError
specified = append(specified, "csi")
}

if vs.Ephemeral != nil {
specified = append(specified, "ephemeral")
}

if vs.Image != nil {
specified = append(specified, "image")
errs = errs.Also(validateImageVolumeSource(vs.Image).ViaField("image"))
Expand All @@ -202,6 +210,9 @@ func validateVolume(ctx context.Context, volume corev1.Volume) *apis.FieldError
if cfg.Features.PodSpecVolumesCSI == config.Enabled {
fieldPaths = append(fieldPaths, "csi")
}
if cfg.Features.PodSpecVolumesEphemeral == config.Enabled {
fieldPaths = append(fieldPaths, "ephemeral")
}
if cfg.Features.PodSpecVolumesImage == config.Enabled {
fieldPaths = append(fieldPaths, "image")
}
Expand Down Expand Up @@ -717,7 +728,7 @@ func validateVolumeMounts(ctx context.Context, mounts []corev1.VolumeMount, volu
}
seenMountPath.Insert(path.Clean(vm.MountPath))

shouldCheckReadOnlyVolume := volumes[vm.Name].EmptyDir == nil && volumes[vm.Name].PersistentVolumeClaim == nil
shouldCheckReadOnlyVolume := volumes[vm.Name].EmptyDir == nil && volumes[vm.Name].PersistentVolumeClaim == nil && volumes[vm.Name].Ephemeral == nil
if shouldCheckReadOnlyVolume && !vm.ReadOnly {
errs = errs.Also((&apis.FieldError{
Message: "volume mount should be readOnly for this type of volume",
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46 changes: 46 additions & 0 deletions pkg/apis/serving/k8s_validation_test.go
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Expand Up @@ -157,6 +157,13 @@ func withPodSpecVolumesCSIEnabled() configOption {
}
}

func withPodSpecVolumesEphemeralEnabled() configOption {
return func(cfg *config.Config) *config.Config {
cfg.Features.PodSpecVolumesEphemeral = config.Enabled
return cfg
}
}

func withPodSpecVolumesImageEnabled() configOption {
return func(cfg *config.Config) *config.Config {
cfg.Features.PodSpecVolumesImage = config.Enabled
Expand Down Expand Up @@ -3492,6 +3499,45 @@ func TestVolumeValidation(t *testing.T) {
},
cfgOpts: []configOption{withPodSpecVolumesImageEnabled()},
want: apis.ErrMissingOneOf("secret", "configMap", "projected", "emptyDir", "image"),
}, {
name: "valid ephemeral volume with feature enabled",
v: corev1.Volume{
Name: "foo",
VolumeSource: corev1.VolumeSource{
Ephemeral: &corev1.EphemeralVolumeSource{
VolumeClaimTemplate: &corev1.PersistentVolumeClaimTemplate{
Spec: corev1.PersistentVolumeClaimSpec{
AccessModes: []corev1.PersistentVolumeAccessMode{corev1.ReadWriteOnce},
},
},
},
},
},
cfgOpts: []configOption{withPodSpecVolumesEphemeralEnabled()},
}, {
name: "ephemeral volume with feature disabled",
v: corev1.Volume{
Name: "foo",
VolumeSource: corev1.VolumeSource{
Ephemeral: &corev1.EphemeralVolumeSource{
VolumeClaimTemplate: &corev1.PersistentVolumeClaimTemplate{
Spec: corev1.PersistentVolumeClaimSpec{
AccessModes: []corev1.PersistentVolumeAccessMode{corev1.ReadWriteOnce},
},
},
},
},
},
want: (&apis.FieldError{
Message: `Ephemeral volume support is disabled, but found Ephemeral volume foo`,
}).Also(&apis.FieldError{Message: "must not set the field(s)", Paths: []string{"ephemeral"}}),
}, {
name: "missing ephemeral volume when required",
v: corev1.Volume{
Name: "foo",
},
cfgOpts: []configOption{withPodSpecVolumesEphemeralEnabled()},
want: apis.ErrMissingOneOf("secret", "configMap", "projected", "emptyDir", "ephemeral"),
}}

for _, test := range tests {
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2 changes: 1 addition & 1 deletion pkg/apis/serving/v1/revision_defaults.go
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Expand Up @@ -145,7 +145,7 @@ func (rs *RevisionSpec) applyDefault(ctx context.Context, container *corev1.Cont

vNames := make(sets.Set[string])
for _, v := range rs.PodSpec.Volumes {
if v.EmptyDir != nil || v.PersistentVolumeClaim != nil {
if v.EmptyDir != nil || v.PersistentVolumeClaim != nil || v.Ephemeral != nil {
vNames.Insert(v.Name)
}
}
Expand Down
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