Cannot migrate to kraft

[ksa75]

strimzi operator - 0.42
kafka version - 3.6.1
k8s version - v1.33.6
annotations:
strimzi.io/kraft: disabled
strimzi.io/node-pools: disabled

My plan was according to https://strimzi.io/blog/2024/03/22/strimzi-kraft-migration/:

1. upgrade to 3.7.0 - ok

2. Start migration by switching annotations:
   strimzi.io/kraft: migrating
   strimzi.io/node-pools: enabled

trying to create nodepool:

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaNodePool
metadata:
name: controller
labels:
strimzi.io/cluster: cluster0
spec:
replicas: 3
roles:
- controller
..

got errors in operators log:
ERROR AbstractOperator:283 - Reconciliation #2375(timer) Kafka(kafka/cluster0): createOrUpdate failed
[KafkaNodePool controller contains invalid roles configuration. In a ZooKeeper-based Kafka cluster, the KafkaNodePool role has to be always set only to the 'broker' role.]

kafkas status:
status:
clusterId:
conditions:

• lastTransitionTime: "2026-01-15T08:40:10.897846625Z"
  message: The .spec.kafka.replicas property in the Kafka custom resource is ignored
  when node pools are used and should be removed from the custom resource.
  reason: UnusedReplicasConfiguration
  status: "True"
  type: Warning
• lastTransitionTime: "2026-01-15T08:40:10.897919649Z"
  message: The .spec.kafka.storage section in the Kafka custom resource is ignored
  when node pools are used and should be removed from the custom resource.
  reason: UnusedStorageConfiguration
  status: "True"
  type: Warning
• lastTransitionTime: "2026-01-15T08:40:13.732662405Z"
  message: 'The Kafka cluster cluster0 is invalid: [KafkaNodePool controller contains
  invalid roles configuration. In a ZooKeeper-based Kafka cluster, the KafkaNodePool
  role has to be always set only to the ''broker'' role.]'
  reason: InvalidResourceException
  status: "True"
  type: NotReady

[scholzj]

It is fine to ask for help, but it is really important to do it the right way. Otherwise it wastes everyones time:

• Please do not open issues for questions!
• Make sure to format everything to make it readable
• Make sure to explain what exactly you are doing, what are you steps, what the errors are etc.
• Make sure to share all configurations (all custom resources) and full logs

Also something that I can see even without a formatting:

• Do not follow a random blog posts as they might get easily outdated. Follow the documentation for the Strimzi version you use.
• You need to be first migrated to KafkaNodePools before migrating to KRaft.
• You should probably consider upgrading to Strimzi 0.45 / Kafka 3.9 first as that has many KRaft related fixes.

[ksa75]

Thanks, Jakub, for detailed guidelines

Im trying to migrate Zookeeper based kafka cluster to kraft
https://strimzi.io/docs/operators/0.45.0/deploying#proc-deploy-migrate-kraft-str

I migrated to KafkaNodePools following https://strimzi.io/docs/operators/0.45.0/deploying#proc-migrating-clusters-node-pools-str
And upgraded to Strimzi 0.45 / Kafka 3.9

My configuration:

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaNodePool
metadata:
  name: kafka
  labels:
    strimzi.io/cluster: cluster0
spec:
  replicas: 3
  roles:
    - broker
  storage:
    type: jbod
    volumes:
      - id: 0
        type: persistent-claim
        size: 10Gi
        class: openebs-lvmpv
        deleteClaim: false
---
apiVersion: kafka.strimzi.io/v1beta2
kind: Kafka
metadata:
  name: cluster0
  annotations:
    strimzi.io/kraft: migrating
    strimzi.io/node-pools: enabled
spec:
  kafka:
    version: 3.9.0
    # replicas: 3
    authorization:
      type: simple
      superUsers:
      - CN=superuser
    listeners:
      - name: external
        port: 9094
        type: ingress
        authentication:
          type: tls
        tls: true
        configuration:
          bootstrap:
            host: bootstrap-kafka-cluster0.apps.k1.example
            annotations:
              kubernetes.io/ingress.class: nginx-pt
          brokers:
          - broker: 0
            host: cluster0-kafka-0.apps.k1.example
            annotations:
              kubernetes.io/ingress.class: nginx-pt
          - broker: 1
            host: cluster0-kafka-1.apps.k1.example
            annotations:
              kubernetes.io/ingress.class: nginx-pt
          - broker: 2
            host: cluster0-kafka-2.apps.k1.example
            annotations:
              kubernetes.io/ingress.class: nginx-pt
      - name: plain
        port: 9092
        type: internal
        tls: false
      - name: tls
        port: 9093
        type: internal
        tls: true
        authentication:
          type: tls
  zookeeper:
    replicas: 3
    storage:
      type: persistent-claim
      size: 1Gi
      class: openebs-lvmpv
      deleteClaim: false

but when I try to add controller node pool:

---
apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaNodePool
metadata:
  name: controller
  labels:
    strimzi.io/cluster: cluster0
spec:
  replicas: 3
  roles:
    - controller
  storage:
    type: jbod
    volumes:
      - id: 0
        type: persistent-claim
        size: 1Gi
        class: openebs-lvmpv
        deleteClaim: false

Get error

2026-01-16 07:13:09 ERROR AbstractOperator:285 - Reconciliation #4018(timer) Kafka(kafka/cluster0): createOrUpdate failed
io.strimzi.operator.common.model.InvalidResourceException: The Kafka cluster cluster0 is invalid: [KafkaNodePool controller contains invalid roles configuration. In a ZooKeeper-based Kafka cluster, the KafkaNodePool role has to be always set only to the 'broker' role.]
at io.strimzi.operator.cluster.model.nodepools.NodePoolUtils.validateNodePools(NodePoolUtils.java:149) ~[io.strimzi.cluster-operator-0.45.0.jar:0.45.0]

[ksa75]

silly mistake as usual)

here:

  annotations:
    strimzi.io/kraft: migration

[scholzj]

No worries, typos ometimes happen 🤷. So is it all good and working now?

[ksa75]

Yes, works as expected

Intresting numbering 3..5
kubectl -n kafka get po -oname

pod/cluster0-controller-3
pod/cluster0-controller-4
pod/cluster0-controller-5

but as is in the manual

[scholzj]

That is because you already have the brokers as 0, 1 and 2 from the ZooKeeper-based cluster. In Kraft, the brokers and controllers have to be numbered from the same sequence. If you would want something different, you can try:

• Use the annotation on the controller node pool to give the controller different IDs - e.g. 100, 101 and 102 (see https://strimzi.io/docs/operators/latest/full/deploying.html#proc-managing-node-pools-ids-str)
• Before the migration, first add brokers 3, 4 and 5, move all data there and remove the brokers 0, 1 and 2. Then during the migration, the contorller nodes will be added as 0, 1 and 2.

But in any case, you cannot have conflicts there. So having brokers 0, 1 and 2 and controllers 0, 1 and 2 is not possible in KRaft.