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Image Registry Operator in OpenShift Container Platform

Image Registry on cloud platforms and OpenStack

The Image Registry Operator installs a single instance of the OpenShift image registry, and manages all registry configuration, including setting up registry storage.

Storage is only automatically configured when you install an installer-provisioned infrastructure cluster on AWS, Azure, GCP, IBM, or OpenStack.

When you install or upgrade an installer-provisioned infrastructure cluster on AWS, Azure, GCP, IBM, or OpenStack, the Image Registry Operator sets the spec.storage.managementState parameter to Managed. If the spec.storage.managementState parameter is set to Unmanaged, the Image Registry Operator takes no action related to storage.

After the control plane deploys, the Operator creates a default configs.imageregistry.operator.openshift.io resource instance based on configuration detected in the cluster.

If insufficient information is available to define a complete configs.imageregistry.operator.openshift.io resource, the incomplete resource is defined and the Operator updates the resource status with information about what is missing.

The Image Registry Operator runs in the openshift-image-registry namespace, and manages the registry instance in that location as well. All configuration and workload resources for the registry reside in that namespace.

The Image Registry Operator’s behavior for managing the pruner is orthogonal to the managementState specified on the ClusterOperator object for the Image Registry Operator. If the Image Registry Operator is not in the Managed state, the image pruner can still be configured and managed by the Pruning custom resource.

However, the managementState of the Image Registry Operator alters the behavior of the deployed image pruner job:

  • Managed: the --prune-registry flag for the image pruner is set to true.

  • Removed: the --prune-registry flag for the image pruner is set to false, meaning it only prunes image metatdata in etcd.

Image Registry on bare metal, Nutanix, and vSphere

Image registry removed during installation

On platforms that do not provide shareable object storage, the OpenShift Image Registry Operator bootstraps itself as Removed. This allows openshift-installer to complete installations on these platform types.

After installation, you must edit the Image Registry Operator configuration to switch the managementState from Removed to Managed.

Image Registry Operator distribution across availability zones

The default configuration of the Image Registry Operator spreads image registry pods across topology zones to prevent delayed recovery times in case of a complete zone failure where all pods are impacted.

The Image Registry Operator defaults to the following when deployed with a zone-related topology constraint:

Image Registry Operator deployed with a zone related topology constraint
  topologySpreadConstraints:
  - labelSelector:
      matchLabels:
        docker-registry: default
    maxSkew: 1
    topologyKey: kubernetes.io/hostname
    whenUnsatisfiable: DoNotSchedule
  - labelSelector:
      matchLabels:
        docker-registry: default
    maxSkew: 1
    topologyKey: node-role.kubernetes.io/worker
    whenUnsatisfiable: DoNotSchedule
  - labelSelector:
      matchLabels:
        docker-registry: default
    maxSkew: 1
    topologyKey: topology.kubernetes.io/zone
    whenUnsatisfiable: DoNotSchedule

The Image Registry Operator defaults to the following when deployed without a zone-related topology constraint, which applies to bare metal and vSphere instances:

Image Registry Operator deployed without a zone related topology constraint
 topologySpreadConstraints:
  - labelSelector:
      matchLabels:
        docker-registry: default
    maxSkew: 1
    topologyKey: kubernetes.io/hostname
    whenUnsatisfiable: DoNotSchedule
  - labelSelector:
      matchLabels:
        docker-registry: default
    maxSkew: 1
    topologyKey: node-role.kubernetes.io/worker
    whenUnsatisfiable: DoNotSchedule

A cluster administrator can override the default topologySpreadConstraints by configuring the configs.imageregistry.operator.openshift.io/cluster spec file. In that case, only the constraints you provide apply.

Additional resources

Image Registry Operator configuration parameters

The configs.imageregistry.operator.openshift.io resource offers the following configuration parameters.

Parameter Description

managementState

Managed: The Operator updates the registry as configuration resources are updated.

Unmanaged: The Operator ignores changes to the configuration resources.

Removed: The Operator removes the registry instance and tear down any storage that the Operator provisioned.

logLevel

Sets logLevel of the registry instance. Defaults to Normal.

The following values for logLevel are supported:

  • Normal

  • Debug

  • Trace

  • TraceAll

httpSecret

Value needed by the registry to secure uploads, generated by default.

operatorLogLevel

The operatorLogLevel configuration parameter provides intent-based logging for the Operator itself and a simple way to manage coarse-grained logging choices that Operators must interpret for themselves. This configuration parameter defaults to Normal. It does not provide fine-grained control.

The following values for operatorLogLevel are supported:

  • Normal

  • Debug

  • Trace

  • TraceAll

proxy

Defines the Proxy to be used when calling master API and upstream registries.

storage

Storagetype: Details for configuring registry storage, for example S3 bucket coordinates. Normally configured by default.

readOnly

Indicates whether the registry instance should reject attempts to push new images or delete existing ones.

requests

API Request Limit details. Controls how many parallel requests a given registry instance will handle before queuing additional requests.

defaultRoute

Determines whether or not an external route is defined using the default hostname. If enabled, the route uses re-encrypt encryption. Defaults to false.

routes

Array of additional routes to create. You provide the hostname and certificate for the route.

rolloutStrategy

Defines rollout strategy for the image registry deployment. Defaults to RollingUpdate.

replicas

Replica count for the registry.

disableRedirect

Controls whether to route all data through the registry, rather than redirecting to the back end. Defaults to false.

spec.storage.managementState

The Image Registry Operator sets the spec.storage.managementState parameter to Managed on new installations or upgrades of clusters using installer-provisioned infrastructure on AWS or Azure.

  • Managed: Determines that the Image Registry Operator manages underlying storage. If the Image Registry Operator’s managementState is set to Removed, then the storage is deleted.

    • If the managementState is set to Managed, the Image Registry Operator attempts to apply some default configuration on the underlying storage unit. For example, if set to Managed, the Operator tries to enable encryption on the S3 bucket before making it available to the registry. If you do not want the default settings to be applied on the storage you are providing, make sure the managementState is set to Unmanaged.

  • Unmanaged: Determines that the Image Registry Operator ignores the storage settings. If the Image Registry Operator’s managementState is set to Removed, then the storage is not deleted. If you provided an underlying storage unit configuration, such as a bucket or container name, and the spec.storage.managementState is not yet set to any value, then the Image Registry Operator configures it to Unmanaged.

Enable the Image Registry default route with the Custom Resource Definition

In OpenShift Container Platform, the Registry Operator controls the OpenShift image registry feature. The Operator is defined by the configs.imageregistry.operator.openshift.io Custom Resource Definition (CRD).

If you need to automatically enable the Image Registry default route, patch the Image Registry Operator CRD.

Procedure

  • Patch the Image Registry Operator CRD:

    $ oc patch configs.imageregistry.operator.openshift.io/cluster --type merge -p '{"spec":{"defaultRoute":true}}'

Configuring additional trust stores for image registry access

The image.config.openshift.io/cluster custom resource can contain a reference to a config map that contains additional certificate authorities to be trusted during image registry access.

Prerequisites

  • The certificate authorities (CA) must be PEM-encoded.

Procedure

You can create a config map in the openshift-config namespace and use its name in AdditionalTrustedCA in the image.config.openshift.io custom resource to provide additional CAs that should be trusted when contacting external registries.

The config map key is the hostname of a registry with the port for which this CA is to be trusted, and the PEM certificate content is the value, for each additional registry CA to trust.

Image registry CA config map example
apiVersion: v1
kind: ConfigMap
metadata:
  name: my-registry-ca
data:
  registry.example.com: |
    -----BEGIN CERTIFICATE-----
    ...
    -----END CERTIFICATE-----
  registry-with-port.example.com..5000: | (1)
    -----BEGIN CERTIFICATE-----
    ...
    -----END CERTIFICATE-----
1 If the registry has the port, such as registry-with-port.example.com:5000, : should be replaced with ...

You can configure additional CAs with the following procedure.

  1. To configure an additional CA:

    $ oc create configmap registry-config --from-file=<external_registry_address>=ca.crt -n openshift-config
    $ oc edit image.config.openshift.io cluster
    spec:
  additionalTrustedCA:
    name: registry-config

Configuring storage credentials for the Image Registry Operator

In addition to the configs.imageregistry.operator.openshift.io and ConfigMap resources, storage credential configuration is provided to the Operator by a separate secret resource located within the openshift-image-registry namespace.

The image-registry-private-configuration-user secret provides credentials needed for storage access and management. It overrides the default credentials used by the Operator, if default credentials were found.

Procedure

  • Create an OpenShift Container Platform secret that contains the required keys.

    $ oc create secret generic image-registry-private-configuration-user --from-literal=KEY1=value1 --from-literal=KEY2=value2 --namespace openshift-image-registry

Additional resources