Kafka Kraft replication factor of 3 - kubernetes

Question

I tried to run Kafka in Raft mode (zookeeper-less) in Kubernetes and everything worked fine with this configuration:
I am curious about how to change the provided configuration to run with a replication factor of 3 for instance?
The fruitful topic was on the github but no one provided Kafka Kraft mode with replication set up.
Statefulset
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: kafka-statefulset
namespace: kafka
labels:
app: kafka-cluster
spec:
serviceName: kafka-svc
replicas: 1
selector:
matchLabels:
app: kafka-cluster
template:
metadata:
labels:
app: kafka-cluster
spec:
containers:
- name: kafka-container
image: 'bitnami/kafka:latest'
ports:
- containerPort: 9092
- containerPort: 9093
env:
- name: KAFKA_BROKER_ID
value: "1"
- name: KAFKA_CFG_NODE_ID
value: "1"
- name: KAFKA_ENABLE_KRAFT
value: "yes"
- name: KAFKA_CFG_PROCESS_ROLES
value: "broker,controller"
- name: KAFKA_CFG_CONTROLLER_LISTENER_NAMES
value: "CONTROLLER"
- name: KAFKA_CFG_LISTENERS
value: "CLIENT://:9092,CONTROLLER://:9093,EXTERNAL://0.0.0.0:9094"
- name: KAFKA_CFG_LISTENER_SECURITY_PROTOCOL_MAP
value: "CONTROLLER:PLAINTEXT,CLIENT:PLAINTEXT,EXTERNAL:PLAINTEXT"
- name: KAFKA_CFG_INTER_BROKER_LISTENER_NAME
value: "CLIENT"
- name: KAFKA_CFG_ADVERTISED_LISTENERS
value: "CLIENT://kafka-statefulset-0.kafka-svc.kafka.svc.cluster.local:9092,EXTERNAL://127.0.0.1:9094"
- name: KAFKA_CFG_CONTROLLER_QUORUM_VOTERS
value: "1#127.0.0.1:9093"
- name: KAFKA_AUTO_CREATE_TOPICS_ENABLE
value: "false"
- name: KAFKA_DEFAULT_REPLICATION_FACTOR
value: "1"
- name: KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR
value: "1"
- name: ALLOW_PLAINTEXT_LISTENER
value: "yes"
Headless service:
apiVersion: v1
kind: Service
metadata:
name: kafka-svc
labels:
app: kafka-cluster
spec:
clusterIP: None
ports:
- name: '9092'
port: 9092
protocol: TCP
targetPort: 9092
selector:
app: kafka-cluster

Answer 1

Finally, I deployed Kafka in Kraft mode with a replication factor of 3 in Kubernetes. I used guidelines within this article. There is a very comprehensive description of how this setup works. I went through the image in docker hub doughgle/kafka-kraft, and there is a link to their Github repo where you can find a script:
#!/bin/bash
NODE_ID=${HOSTNAME:6}
LISTENERS="PLAINTEXT://:9092,CONTROLLER://:9093"
ADVERTISED_LISTENERS="PLAINTEXT://kafka-$NODE_ID.$SERVICE.$NAMESPACE.svc.cluster.local:9092"
CONTROLLER_QUORUM_VOTERS=""
for i in $( seq 0 $REPLICAS); do
if [[ $i != $REPLICAS ]]; then
CONTROLLER_QUORUM_VOTERS="$CONTROLLER_QUORUM_VOTERS$i#kafka-$i.$SERVICE.$NAMESPACE.svc.cluster.local:9093,"
else
CONTROLLER_QUORUM_VOTERS=${CONTROLLER_QUORUM_VOTERS::-1}
fi
done
mkdir -p $SHARE_DIR/$NODE_ID
if [[ ! -f "$SHARE_DIR/cluster_id" && "$NODE_ID" = "0" ]]; then
CLUSTER_ID=$(kafka-storage.sh random-uuid)
echo $CLUSTER_ID > $SHARE_DIR/cluster_id
else
CLUSTER_ID=$(cat $SHARE_DIR/cluster_id)
fi
sed -e "s+^node.id=.*+node.id=$NODE_ID+" \
-e "s+^controller.quorum.voters=.*+controller.quorum.voters=$CONTROLLER_QUORUM_VOTERS+" \
-e "s+^listeners=.*+listeners=$LISTENERS+" \
-e "s+^advertised.listeners=.*+advertised.listeners=$ADVERTISED_LISTENERS+" \
-e "s+^log.dirs=.*+log.dirs=$SHARE_DIR/$NODE_ID+" \
/opt/kafka/config/kraft/server.properties > server.properties.updated \
&& mv server.properties.updated /opt/kafka/config/kraft/server.properties
kafka-storage.sh format -t $CLUSTER_ID -c /opt/kafka/config/kraft/server.properties
exec kafka-server-start.sh /opt/kafka/config/kraft/server.properties
This script is necessary for setting proper configuration one by one to pods/brokers.
Then I built my own image with the latest version of Kafka, Scala and openjdk 17:
FROM openjdk:17-bullseye
ENV KAFKA_VERSION=3.3.1
ENV SCALA_VERSION=2.13
ENV KAFKA_HOME=/opt/kafka
ENV PATH=${PATH}:${KAFKA_HOME}/bin
LABEL name="kafka" version=${KAFKA_VERSION}
RUN wget -O /tmp/kafka_${SCALA_VERSION}-${KAFKA_VERSION}.tgz https://downloads.apache.org/kafka/${KAFKA_VERSION}/kafka_${SCALA_VERSION}-${KAFKA_VERSION}.tgz \
&& tar xfz /tmp/kafka_${SCALA_VERSION}-${KAFKA_VERSION}.tgz -C /opt \
&& rm /tmp/kafka_${SCALA_VERSION}-${KAFKA_VERSION}.tgz \
&& ln -s /opt/kafka_${SCALA_VERSION}-${KAFKA_VERSION} ${KAFKA_HOME} \
&& rm -rf /tmp/kafka_${SCALA_VERSION}-${KAFKA_VERSION}.tgz
COPY ./entrypoint.sh /
RUN ["chmod", "+x", "/entrypoint.sh"]
ENTRYPOINT ["/entrypoint.sh"]
and here is the Kubernetes configuration:
apiVersion: v1
kind: Namespace
metadata:
name: kafka-kraft
---
apiVersion: v1
kind: PersistentVolume
metadata:
name: kafka-pv-volume
labels:
type: local
spec:
storageClassName: manual
capacity:
storage: 1Gi
accessModes:
- ReadWriteOnce
hostPath:
path: '/path/to/dir'
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: kafka-pv-claim
namespace: kafka-kraft
spec:
storageClassName: manual
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 500Mi
---
apiVersion: v1
kind: Service
metadata:
name: kafka-svc
labels:
app: kafka-app
namespace: kafka-kraft
spec:
clusterIP: None
ports:
- name: '9092'
port: 9092
protocol: TCP
targetPort: 9092
selector:
app: kafka-app
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
name: kafka
labels:
app: kafka-app
namespace: kafka-kraft
spec:
serviceName: kafka-svc
replicas: 3
selector:
matchLabels:
app: kafka-app
template:
metadata:
labels:
app: kafka-app
spec:
volumes:
- name: kafka-storage
persistentVolumeClaim:
claimName: kafka-pv-claim
containers:
- name: kafka-container
image: me/kafka-kraft
ports:
- containerPort: 9092
- containerPort: 9093
env:
- name: REPLICAS
value: '3'
- name: SERVICE
value: kafka-svc
- name: NAMESPACE
value: kafka-kraft
- name: SHARE_DIR
value: /mnt/kafka
- name: CLUSTER_ID
value: oh-sxaDRTcyAr6pFRbXyzA
- name: DEFAULT_REPLICATION_FACTOR
value: '3'
- name: DEFAULT_MIN_INSYNC_REPLICAS
value: '2'
volumeMounts:
- name: kafka-storage
mountPath: /mnt/kafka
I am not 100% sure if this setup works like with a stable zookeeper setup, but it is currently sufficient for me for the testing phase.
UPDATE:
Kafka Kraft is production ready in release 3.3.1