Configure the OpenShift Image Registry backed by OpenShift Container Storage

1. Requirements

Note: This scenario supposes you already have Red Hat OpenShift Container Storage 4 running inside your Red Hat OpenShift Container Platform 4 environment. Alternatively, follow the instructions in the Deploying OpenShift Container Storage 4 to OpenShift 4 Blog to set up an OpenShift Container Platform 4.2.14+ cluster using OpenShift Container Storage 4.
In order to verify the presence of OpenShift Container Storage, please run:

oc describe project openshift-storage|grep Status

The result of the above command should be similar to:

Status:         Active

2. Registry Introduction

OpenShift Container Platform provides a built in Container Image Registry which runs as a standard workload on the cluster. A registry is typically used as a publication target for images built on the cluster, as well as a source of images for workloads running on the cluster.
In addition, it is integrated into the cluster user authentication and authorization system, which means that access to create and retrieve images is controlled by defining user permissions on the image resources.

3. Image Registry Operator

The Registry is configured and managed by an infrastructure operator. The Image Registry Operator installs a single instance of the OpenShift Container Platform registry, and it manages all configuration of the registry, including setting up registry storage when you install an installer-provisioned infrastructure cluster on AWS, GCP, Azure, or OpenStack.
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.
In case you want to see detailed information about the registry operator, run:

oc describe configs.imageregistry.operator.openshift.io

4. Registry Storage Requirements

A registry needs to have storage in order to store its contents. Image data is stored in two locations. The actual image data is stored in a configurable storage location such as cloud storage or a filesystem volume.
The image metadata, which is exposed by the standard cluster APIs and is used to perform access control, is stored as standard API resources, specifically images and imagestreams.

4.1. Project

The registry is arranged in a Project (namespace) named: ‘openshift-image-registry’
To get more information about this project, run the following oc command:

oc describe project openshift-image-registry
Name:           openshift-image-registry
Created:        3 hours ago
Labels:         openshift.io/cluster-monitoring=true
Annotations:        openshift.io/node-selector=
            openshift.io/sa.scc.mcs=s0:c18,c17
            openshift.io/sa.scc.supplemental-groups=1000340000/10000
            openshift.io/sa.scc.uid-range=1000340000/10000
Display Name:       <none>
Description:        <none>
Status:         Active
Node Selector:      <none>
Quota:          <none>
Resource limits:    <none>

4.2. Pods

To view the registry related pods, run the command:

oc get pods -n openshift-image-registry

(The NAME of your machines will be different than shown below)

NAME                                               READY   STATUS    RESTARTS   AGE
cluster-image-registry-operator-74465655b4-gq44m   2/2     Running   0          3h16m
image-registry-7489584ddc-jhw2j                    1/1     Running   0          3h16m
node-ca-4x477                                      1/1     Running   0          116m
node-ca-d82rv                                      1/1     Running   0          3h16m
node-ca-gxd8r                                      1/1     Running   0          3h16m
node-ca-kjp28                                      1/1     Running   0          3h16m
node-ca-lvb48                                      1/1     Running   0          116m
node-ca-ndwhh                                      1/1     Running   0          3h16m
node-ca-nwstp                                      1/1     Running   0          116m
node-ca-pwrrs                                      1/1     Running   0          3h16m

5. Review the current Registry Operator configuration settings

Let’s review the current Registry settings first. To do so, please run the command:

oc edit configs.imageregistry.operator.openshift.io/cluster
# Please edit the object below. Lines beginning with a '#' will be ignored,
# and an empty file will abort the edit. If an error occurs while saving this file will be
# reopened with the relevant failures.
#
apiVersion: imageregistry.operator.openshift.io/v1
kind: Config
metadata:
  creationTimestamp: "2019-10-28T09:07:09Z"
  finalizers:
  - imageregistry.operator.openshift.io/finalizer
  generation: 3
  name: cluster
  resourceVersion: "16463"
  selfLink: /apis/imageregistry.operator.openshift.io/v1/configs/cluster
  uid: 52880e6b-f962-11e9-8995-12a861d1434e
spec:
  defaultRoute: true
  httpSecret: 0c394aabee8e6a9ef8aa2c927c8f8c487f8ad3249ff67794a8685af4f76c72811c97ee4ddf936602dd9fca12e198c4eff413130568a4c356d7b6f14f805bcb59
  logging: 2
  managementState: Managed
  proxy:
    http: ""
    https: ""
    noProxy: ""
  readOnly: false
  replicas: 1
  requests:
    read:
      maxInQueue: 0
      maxRunning: 0
      maxWaitInQueue: 0s
    write:
      maxInQueue: 0
      maxRunning: 0
      maxWaitInQueue: 0s
  storage:
    s3:
      bucket: cluster-ocs-f562-9d4rh-image-registry-us-east-1-rjqkgcsxlotmwm
      encrypt: true
      keyID: ""
      region: us-east-1
      regionEndpoint: ""
status:
  conditions:
  - lastTransitionTime: "2019-10-28T09:07:10Z"
reason: S3 Bucket Exists
    status: "True"
    type: StorageExists
  - lastTransitionTime: "2019-10-28T09:07:10Z"
    message: Public access to the S3 bucket and its contents have been successfully
      blocked.
    reason: Public Access Block Successful
    status: "True"
    type: StoragePublicAccessBlocked
  - lastTransitionTime: "2019-10-28T09:07:10Z"
    message: Tags were successfully applied to the S3 bucket
    reason: Tagging Successful
    status: "True"
    type: StorageTagged
  - lastTransitionTime: "2019-10-28T09:07:10Z"
    message: Default AES256 encryption was successfully enabled on the S3 bucket
    reason: Encryption Successful
    status: "True"
    type: StorageEncrypted
  - lastTransitionTime: "2019-10-28T09:07:10Z"
    message: Default cleanup of incomplete multipart uploads after one (1) day was
    successfully enabled
    reason: Enable Cleanup Successful
    status: "True"
    type: StorageIncompleteUploadCleanupEnabled
  - lastTransitionTime: "2019-10-28T09:07:56Z"
    message: The registry is ready
    reason: Ready
    status: "True"
    type: Available
  - lastTransitionTime: "2019-10-28T09:18:32Z"
    message: The registry is ready
    reason: Ready
    status: "False"
    type: Progressing
  - lastTransitionTime: "2019-10-28T09:07:11Z"
    status: "False"
    type: Degraded
  - lastTransitionTime: "2019-10-28T09:07:11Z"
    status: "False"
    type: Removed
  observedGeneration: 3
  readyReplicas: 0
  storage:
    s3:
      bucket: cluster-ocs-f562-9d4rh-image-registry-us-east-1-rjqkgcsxlotmwm
      encrypt: true
      keyID: ""
      region: us-east-1
      regionEndpoint: ""
  storageManaged: true

Note: The storage`` designation currently refers tos3and abucket` name. This is an initial deployment of OCP4 on AWS infrastructure.

storage:
    s3:
      bucket: cluster-ocs-f562-9d4rh-image-registry-us-east-1-rjqkgcsxlotmwm
      encrypt: true
      keyID: ""
      region: us-east-1
      regionEndpoint: ""

Close the VI editor by first pressing ESC and then : followed by q! and ENTER

6. Moving the registry storage to OpenShift Container Storage

In this section we will change the registry storage to OpenShift Container Storage, where it will consume CephFS RWX storage, as multiple pods will need to access the storage concurrently.

6.1. Storage Class

First we want to make sure that a CephFS storageclass is present, in order to create a Persistent Volume Claim for the registry storage.
To check for presence of an existing CephFS storage class, please run the following command:

oc get sc

This should result in an outcome similar to:

NAME                                    PROVISIONER                             AGE
gp2                                     kubernetes.io/aws-ebs                   5h57m
ocs-storagecluster-ceph-rbd (default)   openshift-storage.rbd.csi.ceph.com      4h5m
ocs-storagecluster-cephfs               openshift-storage.cephfs.csi.ceph.com   4h5m
openshift-storage.noobaa.io             openshift-storage.noobaa.io/obc         3h59m

According to the above output, there is already a storageclass named ocs-storagecluster-cephfs

6.2. PVC (Persistent Volume Claim)

In this step we will setup a pvc named ocs4registry addressed to our storageclass named ocs-storagecluster-cephfs, which is going to be used for storing registry data.
First, please make sure to be inside the openshift-image-registry project.

oc project openshift-image-registry

In order to create the pvc, please run the following command:

oc create -f <(echo '{
   "apiVersion": "v1",
   "kind": "PersistentVolumeClaim",
   "metadata": {
     "name": "ocs4registry"
   },
   "spec": {
     "storageClassName": "ocs-storagecluster-cephfs",
     "accessModes": [ "ReadWriteMany" ],
     "resources": {
       "requests": { "storage": "100Gi"
     }
   }
 }
}');

This should result in:

persistentvolumeclaim/ocs4registry created

To check if it worked out well:

oc get pvc

Example output:

NAME           STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS                AGE
ocs4registry   Bound    pvc-b7339457-fb23-11e9-846d-0a3016334dd1   100Gi      RWX            ocs-storagecluster-cephfs   60s

6.3. Configure the Image Registry to use the newly created PVC

In this section we will instruct the Registry Operator to use the CephFS-backed RWX PVC.

Note: This method of moving the registry to OpenShift Container Storage will work exactly the same for OpenShift Container Platform on VMware infrastructure.
Now configure the registry to use OpenShift Container Storage. Find the storage: stanza and remove it and everything below it. Everything above it should remain in place. Then put the following instead:

oc edit configs.imageregistry.operator.openshift.io

Find the storage section and add the following:

 storage:
    pvc:
     claim: ocs4registry

Close the VI editor by first pressing ESC and then : followed by wq! and ENTER
Then check the /registry mountpoint inside the image-registry pod, as a validation that the pod now uses the OCS pvc instead of the s3 resources on AWS. Here is how to do this:

oc get pods

Note: The NAME of your machines will be different than shown below

Example output:

NAME                                               READY   STATUS    RESTARTS   AGE
cluster-image-registry-operator-6d65bcbd4b-7h6b6   2/2     Running   0          8h
image-registry-6c4dbbcdbb-9bl8w                    1/1     Running   0          8m59s
node-ca-26q5d                                      1/1     Running   0          8h
node-ca-6tdrs                                      1/1     Running   0          8h
node-ca-9jdwt                                      1/1     Running   0          8h
node-ca-g6dr5                                      1/1     Running   0          8h
node-ca-jt7w8                                      1/1     Running   0          8h
node-ca-r9qtx                                      1/1     Running   0          7h41m
node-ca-srgv9                                      1/1     Running   0          7h41m
node-ca-wg2xs                                      1/1     Running   0          7h41m

We now open a remote shell on the registry pod. This is the podname that starts with image-registry-*

Note: The NAME of your registry pod will be different than shown below

oc rsh image-registry-6c4dbbcdbb-9bl8w

Once connected, a bash prompt appears. You are now running a bash shell on the pod itself.
From within this remote shell, we can run both the df -h and/or mount command, which shows the result information from pod perspective:

sh-4.2$ df -h | grep registry

This results in the following output:

172.30.107.130:6789,172.30.82.116:6789,172.30.125.23:6789:/volumes/csi/csi-vol-5b88bd0e-fc09-11e9-9939-0a580a820206  100G     0  100G   0% /registry

Another approach to take could be to use the mount command.

sh-4.2$ mount | grep registry

Resulting in the following output:

172.30.107.130:6789,172.30.82.116:6789,172.30.125.23:6789:/volumes/csi/csi-vol-5b88bd0e-fc09-11e9-9939-0a580a820206 on /registry type ceph (rw,relatime,name=csi-cephfs-node,secret=<hidden>,acl,mds_namespace=ocs-storagecluster-cephfilesystem)

At this point, the image registry should be using the OCS RWX volume, backed by CephFS.
In the output from either command, it is shown that the /registry filesystem mount originates from /volumes/csi/csi-vol-5b88bd0e-fc09-11e9-9939-0a580a820206 sourced from Ceph nodes, managed by the rook operator.
As a result from the df -h command, we can verify it has 100Gi available space. The mount command shows which options were used when mounting the /registry filesystem slice.
You can exit the pod remote shell rsh by either pressing Ctrl+D or by executing exit.

Resources and Feedback

To find out more about OpenShift Container Storage or to take a test drive, visit https://www.openshift.com/products/container-storage/.

If you would like to learn more about what the OpenShift Container Storage team is up to or provide feedback on any of the new 4.2 features, take this brief 3-minute survey.

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Containers, Storage
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