Ingress classes

By default, this is disabled.

IngressClass syncing allows virtual clusters to use ingress controllers from the host cluster. Typically, each virtual cluster needs its own ingress controller to handle incoming traffic. With IngressClass syncing enabled, virtual clusters can reference IngressClass resources from the host cluster instead.

You can enable this feature to sync IngressClass resources from the host cluster to the virtual cluster. Add labels to IngressClass resources in your host cluster and configure vCluster to sync only those that match specific label selectors. When you create an Ingress resource in the virtual cluster that references a synced IngressClass, the host cluster's ingress controller handles the traffic routing.

This saves resources since you don't need separate ingress controllers in every virtual cluster. It also gives you centralized control over which ingress capabilities teams can access.

This approach is useful in scenarios where selective access to ingress configurations is required. Common use cases include:

• Development environments: Sync only the IngressClass resources required for development clusters to reduce noise and avoid unnecessary exposure.
• Multi-tenancy: Enable teams to use their own IngressClass resources while sharing a single host cluster.
• Security: Restrict the IngressClass resources available in the virtual cluster to enforce access control and prevent unintended configurations.

Enable syncing

When enabled, vCluster takes control of all IngressClass resources in the virtual cluster. It only allows IngressClass resources that are synced from the host cluster to exist.

This example configuration enables syncing all IngressClass resources from the host cluster to the virtual cluster:

sync:
  fromHost:
    ingressClasses:
      enabled: true

If you try to create the IngressClass resource directly in the virtual cluster, using for example kubectl create or kubectl apply, vCluster detects it and deletes it immediately. This prevents conflicts between locally-created IngressClass resources and those synced from the host cluster, ensuring that only IngressClass resources from the host cluster exist in the virtual cluster.

IngressClass resource limitation

When enabled, IngressClass resource creation can only occur in the host cluster. Any IngressClass resources created in the virtual cluster will be deleted.

How syncing works

When IngressClass syncing is enabled, vCluster can use a label selector to control which IngressClass and Ingress resources are synchronized between the host and virtual clusters. This affects the resource types with separate unidirectional sync flows:

• IngressClass resources (host → virtual): vCluster syncs IngressClass resources from the host cluster to the virtual cluster. You cannot create IngressClass resources directly in the virtual cluster. If a selector is defined, only IngressClass resources matching the selector will sync. If no selector is defined, all IngressClass resources are synced.

• Ingress resources (virtual → host): vCluster syncs Ingress resources from the virtual cluster to the host cluster only if any of the following is true:

  • No selector is defined for IngressClass syncing, which allows all Ingress resources to sync regardless of the IngressClassName.
  • The Ingress's IngressClassName references a IngressClass resource that matches the selector and is synced from the host cluster.
  • The Ingress has an empty IngressClassName field.

The same selector controls both sync flows. The selector determines which IngressClass resources are imported from the host cluster and which Ingress resources can sync to the host cluster based on the referenced IngressClass resource.

Use selectors to filter

Selectors provide precise control over which IngressClass resources get synced from the host cluster and which Ingress resources gets synced to the host cluster. vCluster supports two types of selector criteria that follow standard Kubernetes label selector syntax.

Filter with matchLabels

The matchLabels selector defines exact label key-value pairs that must be present on an IngressClass for it to be synced. This provides straightforward filtering based on specific labels.

The following example syncs only IngressClass resources with a environment: development label:

Example with matchLabels

sync:
  toHost:
    ingresses:
      enabled: true
  fromHost:
    ingressClasses:
      enabled: true
      selector:
        matchLabels:
          environment: development

Filter with matchExpressions

The matchExpressions selector allows more flexible, set-based filtering with support for multiple operators:

• In: Select all resources that has a specific key and the value is in the set of values
• NotIn: Select all resources that has a specific key and the value is not in the set of values
• Exists: Select all resources including a label with the key; no values are checked
• DoesNotExist: Select all resources without a label with the key; no values are checked

The following example syncs IngressClass resources where the key of the label is kubernetes.io/ingress.class and the value of that label is either nginx or traefik:

Example with matchExpressions

sync:
  toHost:
    ingresses:
      enabled: true
  fromHost:
    ingressClasses:
      enabled: true
      selector:
        matchExpressions:
          - key: kubernetes.io/ingress.class
            operator: In
            values:
              - nginx
              - traefik

Combined filter criteria

Label conditions are additive meaning all specified label conditions must match for the IngressClass resource to be selected to be synced. This means that if you define multiple matchLabels and matchExpressions, the IngressClass resource must satisfy all criteria to be synced to the virtual cluster.

The following example syncs IngressClass resources that match both label and expression criteria:

Example with matchLabels and matchExpressions

sync:
  toHost:
    ingresses:
      enabled: true
  fromHost:
    ingressClasses:
      enabled: true
      selector:
        matchLabels:
          environment: development
        matchExpressions:
          - key: kubernetes.io/ingress.class
            operator: In
            values:
              - nginx
              - traefik

In this example, the IngressClass must have the following labels to sync to the virtual cluster:

• environment: development
• Either kubernetes.io/ingress.class:nginx or kubernetes.io/ingress.class:traefik

Sync behavior considerations

Resource lifecycle

Synced IngressClass resources function like any other Kubernetes resource in the virtual cluster. You can view them with kubectl get ingressclass and reference them in your Ingress resource specifications with the IngressClassName field.

When you modify the IngressClass resource in the host cluster, vCluster re-evaluates whether it still matches the selector criteria. If the IngressClass continues to match, vCluster updates the corresponding resource in the virtual cluster to reflect the changes. If the IngressClass no longer matches the selector criteria, vCluster removes it from the virtual cluster.

The selector system acts as both a resource filter and a validation mechanism. As a resource filter, it ensures that vCluster creates only IngressClass resources matching the defined selector criteria. The selector also functions as a creation validation mechanism - when you create Ingress resources in the virtual cluster, the resources can only reference IngressClass resources that exist in the virtual cluster.

Orphaned resources

When vCluster removes a synced IngressClass from the virtual cluster due to selector changes or deletion from the host cluster, any Ingress resources that reference it remain in the virtual and host clusters. These orphaned Ingress resources stop receiving updates but vCluster does not automatically delete them to prevent unintended data loss. To remove these orphaned resources, you must delete them manually in the virtual and host clusters. This manual approach ensures that you maintain full control over resource cleanup and can verify that deletions are intentional.

Error handling and troubleshooting

When the IngressClass resource doesn't match the selector criteria during evaluation, vCluster logs a warning in the syncer pod's output to help with troubleshooting and monitoring. This logging provides visibility into which resources are being filtered out and why.

When you creates the Ingress resource that references a IngressClass not matching the selector criteria, several things occur to provide clear feedback:

• The Ingress fails to sync to the host cluster
• vCluster records an event on the Ingress resource in the virtual cluster
• The event indicates that the specified IngressClass is not available according to the current selector configuration

The error output appears as a Kubernetes event that you can view using kubectl describe. The event message clearly states that the Ingress resource was not synced because the referenced IngressClass does not match the defined selector criteria.

The error output looks like this:

Example error handling output

vcluster-virtual-cluster-1:~$ kubectl describe ingress my-ingress
Name:                       my-ingress
Namespace:                  default
IngressClass:     traefik
Events:
  Type     Reason            Age   From                   Message
  ----     ------            ----  ----                    -------
  Warning  SyncWarning       10s   ingress-syncer      did not sync ingress "my-ingress" to host because it does not match the selector under 'sync.fromHost.ingressClasses.selector'

Config reference

ingressClasses required object pro

IngressClasses defines if ingress classes should get synced from the host cluster to the virtual cluster, but not back.

enabled required boolean false pro

Enabled defines if this option should be enabled.

patches required object[] pro

Patches patch the resource according to the provided specification.

path required string pro

Path is the path within the patch to target. If the path is not found within the patch, the patch is not applied.

expression required string pro

Expression transforms the value according to the given JavaScript expression.

reverseExpression required string pro

ReverseExpression transforms the value according to the given JavaScript expression.

reference required object pro

Reference treats the path value as a reference to another object and will rewrite it based on the chosen mode automatically. In single-namespace mode this will translate the name to "vxxxxxxxxx" to avoid conflicts with other names, in multi-namespace mode this will not translate the name.

apiVersion required string pro

APIVersion is the apiVersion of the referenced object.

apiVersionPath required string pro

APIVersionPath is optional relative path to use to determine the kind. If APIVersionPath is not found, will fallback to apiVersion.

kind required string pro

Kind is the kind of the referenced object.

kindPath required string pro

KindPath is the optional relative path to use to determine the kind. If KindPath is not found, will fallback to kind.

namePath required string pro

NamePath is the optional relative path to the reference name within the object.

namespacePath required string pro

NamespacePath is the optional relative path to the reference namespace within the object. If omitted or not found, namespacePath equals to the metadata.namespace path of the object.

labels required object pro

Labels treats the path value as a labels selector.

selector required object pro

Selector defines the selector to use for the resource. If not set, all resources of that type will be synced.

matchLabels required object pro

matchExpressions required object[] pro

key required string pro

operator required string pro

values required string[] pro