Migrate existing Hyper-Converged Database (HCD), DataStax Enterprise (DSE), or Apache Cassandra® clusters to Mission Control using the add a new datacenter method

apiVersion: missioncontrol.datastax.com/v1beta2
kind: MissionControlCluster
metadata:
  name: NEW_CLUSTER_NAME
spec:
  k8ssandra:
    externalDatacenters:
      - name: CURRENT_DC  # Your existing datacenter not managed by Mission Control
    cassandra:
      serverType: "SERVER_TYPE"  # Use "hcd" for HCD clusters, "dse" for DSE clusters, "cassandra" for Apache Cassandra
      serverVersion: "SERVER_VERSION"  # Match your existing cluster version
      clusterName: "CURRENT_CLUSTER_NAME"  # Must match existing cluster name
      datacenters:
        - metadata:
            name: NEW_DC  # New Mission Control-managed datacenter
          k8sContext: TARGET_CLUSTER
          size: 3
          racks:
            - name: rack1
              nodeAffinityLabels:
                topology.kubernetes.io/zone: AVAILABILITY_ZONE_1
            - name: rack2
              nodeAffinityLabels:
                topology.kubernetes.io/zone: AVAILABILITY_ZONE_2
            - name: rack3
              nodeAffinityLabels:
                topology.kubernetes.io/zone: AVAILABILITY_ZONE_3
          config:
            cassandraYaml:
              additionalSeeds:
                - "SEED_NODE_1"
                - "SEED_NODE_2"
                - "SEED_NODE_3"
              # Do not manually configure seed_provider
              # Mission Control automatically manages seed nodes within the new datacenter

kubectl apply -f CLUSTER_NAME.yaml

kubectl get cassandradatacenter DATACENTER_NAME -o jsonpath='{.status.conditions[?(@.type=="Ready")].status}: {.status.cassandraOperatorProgress}'

kubectl get cassandradatacenter DATACENTER_NAME -o yaml

ALTER KEYSPACE KEYSPACE_NAME
WITH replication = {
  'class': 'NetworkTopologyStrategy',
  'EXISTING_DATACENTER': 3,
  'NEW_DATACENTER': 3
};

apiVersion: control.k8ssandra.io/v1alpha1
kind: CassandraTask
metadata:
  name: TASK_NAME
spec:
  datacenter:
    name: DATACENTER_NAME
    namespace: NAMESPACE
  jobs:
    - name: rebuild-from-legacy
      command: rebuild
      args:
        source_datacenter: EXISTING_DATACENTER

kubectl apply -f TASK_NAME.yaml

kubectl get cassandratask TASK_NAME -o jsonpath='{.status.conditions[?(@.type=="Complete")].status}: Succeeded={.status.succeeded}/{.status.active}'

kubectl get cassandratask TASK_NAME -o yaml

status:
  completionTime: "2026-02-23T22:15:30Z"
  conditions:
  - lastTransitionTime: "2026-02-23T22:15:30Z"
    status: "True"
    type: Complete
  succeeded: 3

kubectl exec -it POD_NAME -n NAMESPACE -- nodetool netstats

kubectl get service -n CLUSTER_NAMESPACE

# Verify new datacenter nodes are up and part of the cluster
kubectl exec -it DATACENTER_NAME-RACK_NAME-sts-NODE_NUMBER -c cassandra -- nodetool status

ALTER KEYSPACE KEYSPACE_NAME
WITH replication = {
  'class': 'NetworkTopologyStrategy',
  'dc-mc': 3
};

apiVersion: control.k8ssandra.io/v1alpha1
kind: CassandraTask
metadata:
  name: TASK_NAME
spec:
  datacenter:
    name: DATACENTER_NAME
    namespace: NAMESPACE
  jobs:
    - name: cleanup
      command: cleanup

# On each node in the old datacenter
nodetool decommission

kubectl exec -it DATACENTER_NAME-RACK_NAME-sts-NODE_NUMBER -c cassandra -- nodetool status

kubectl logs -n CLUSTER_NAME -l app=cassandra