Chapter 2. Image Registry Operator in OpenShift Container Platform
2.1. 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-registryflag for the image pruner is set totrue. -
Removed: the--prune-registryflag for the image pruner is set tofalse, meaning it only prunes image metatdata in etcd.
2.2. Image Registry on bare metal, Nutanix, and vSphere
2.2.1. 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.
2.3. 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.
2.4. Additional resources
2.5. Image Registry Operator configuration parameters
The configs.imageregistry.operator.openshift.io resource offers the following configuration parameters.
| Parameter | Description |
|---|---|
|
|
|
|
|
Sets
The following values for
|
|
| Value needed by the registry to secure uploads, generated by default. |
|
|
The
The following values for
|
|
| Defines the Proxy to be used when calling master API and upstream registries. |
|
|
|
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| Indicates whether the registry instance should reject attempts to push new images or delete existing ones. |
|
| API Request Limit details. Controls how many parallel requests a given registry instance will handle before queuing additional requests. |
|
|
Determines whether or not an external route is defined using the default hostname. If enabled, the route uses re-encrypt encryption. Defaults to |
|
| Array of additional routes to create. You provide the hostname and certificate for the route. |
|
|
Defines rollout strategy for the image registry deployment. Defaults to |
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| Replica count for the registry. |
|
|
Controls whether to route all data through the registry, rather than redirecting to the back end. Defaults to |
|
|
The Image Registry Operator sets the
|
2.6. 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}}'
2.7. 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.
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
2.8. 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
