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Disaster recovery for a hosted cluster within an AWS region

In a situation where you need disaster recovery (DR) for a hosted cluster, you can recover a hosted cluster to the same region within AWS. For example, you need DR when the upgrade of a management cluster fails and the hosted cluster is in a read-only state.

Hosted control planes is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

The DR process involves three main steps:

  1. Backing up the hosted cluster on the source management cluster

  2. Restoring the hosted cluster on a destination management cluster

  3. Deleting the hosted cluster from the source management cluster

Your workloads remain running during the process. The Cluster API might be unavailable for a period, but that will not affect the services that are running on the worker nodes.

Both the source management cluster and the destination management cluster must have the --external-dns flags to maintain the API server URL, as shown in this example:

Example: External DNS flags
--external-dns-provider=aws \
--external-dns-credentials=<AWS Credentials location> \
--external-dns-domain-filter=<DNS Base Domain>

That way, the server URL ends with https://api-sample-hosted.sample-hosted.aws.openshift.com.

If you do not include the --external-dns flags to maintain the API server URL, the hosted cluster cannot be migrated.

Example environment and context

Consider an scenario where you have three clusters to restore. Two are management clusters, and one is a hosted cluster. You can restore either the control plane only or the control plane and the nodes. Before you begin, you need the following information:

  • Source MGMT Namespace: The source management namespace

  • Source MGMT ClusterName: The source management cluster name

  • Source MGMT Kubeconfig: The source management kubeconfig file

  • Destination MGMT Kubeconfig: The destination management kubeconfig file

  • HC Kubeconfig: The hosted cluster kubeconfig file

  • SSH key file: The SSH public key

  • Pull secret: The pull secret file to access the release images

  • AWS credentials

  • AWS region

  • Base domain: The DNS base domain to use as an external DNS

  • S3 bucket name: The bucket in the AWS region where you plan to upload the etcd backup

This information is shown in the following example environment variables.

Example environment variables
SSH_KEY_FILE=${HOME}/.ssh/id_rsa.pub
BASE_PATH=${HOME}/hypershift
BASE_DOMAIN="aws.sample.com"
PULL_SECRET_FILE="${HOME}/pull_secret.json"
AWS_CREDS="${HOME}/.aws/credentials"
AWS_ZONE_ID="Z02718293M33QHDEQBROL"

CONTROL_PLANE_AVAILABILITY_POLICY=SingleReplica
HYPERSHIFT_PATH=${BASE_PATH}/src/hypershift
HYPERSHIFT_CLI=${HYPERSHIFT_PATH}/bin/hypershift
HYPERSHIFT_IMAGE=${HYPERSHIFT_IMAGE:-"quay.io/${USER}/hypershift:latest"}
NODE_POOL_REPLICAS=${NODE_POOL_REPLICAS:-2}

# MGMT Context
MGMT_REGION=us-west-1
MGMT_CLUSTER_NAME="${USER}-dev"
MGMT_CLUSTER_NS=${USER}
MGMT_CLUSTER_DIR="${BASE_PATH}/hosted_clusters/${MGMT_CLUSTER_NS}-${MGMT_CLUSTER_NAME}"
MGMT_KUBECONFIG="${MGMT_CLUSTER_DIR}/kubeconfig"

# MGMT2 Context
MGMT2_CLUSTER_NAME="${USER}-dest"
MGMT2_CLUSTER_NS=${USER}
MGMT2_CLUSTER_DIR="${BASE_PATH}/hosted_clusters/${MGMT2_CLUSTER_NS}-${MGMT2_CLUSTER_NAME}"
MGMT2_KUBECONFIG="${MGMT2_CLUSTER_DIR}/kubeconfig"

# Hosted Cluster Context
HC_CLUSTER_NS=clusters
HC_REGION=us-west-1
HC_CLUSTER_NAME="${USER}-hosted"
HC_CLUSTER_DIR="${BASE_PATH}/hosted_clusters/${HC_CLUSTER_NS}-${HC_CLUSTER_NAME}"
HC_KUBECONFIG="${HC_CLUSTER_DIR}/kubeconfig"
BACKUP_DIR=${HC_CLUSTER_DIR}/backup

BUCKET_NAME="${USER}-hosted-${MGMT_REGION}"

# DNS
AWS_ZONE_ID="Z07342811SH9AA102K1AC"
EXTERNAL_DNS_DOMAIN="hc.jpdv.aws.kerbeross.com"

Overview of the backup and restore process

The backup and restore process works as follows:

  1. On management cluster 1, which you can think of as the source management cluster, the control plane and workers interact by using the external DNS API. The external DNS API is accessible, and a load balancer sits between the management clusters.

    Diagram that shows the workers accessing the external DNS API and the external DNS API pointing to the control plane through a load balancer

  2. You take a snapshot of the hosted cluster, which includes etcd, the control plane, and the worker nodes. During this process, the worker nodes continue to try to access the external DNS API even if it is not accessible, the workloads are running, the control plane is saved in a local manifest file, and etcd is backed up to an S3 bucket. The data plane is active and the control plane is paused.