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Topology Cluster
A Kafka topology cluster is a comprised of two groups of kafka nodes (eg. pods) where one group of nodes are assigned to controller role which manages cluster metadata & participates in leader election. Outer group of nodes are assigned to dedicated broker roles that only act as Kafka broker for message publishing and subscribing. Topology mode clustering is suitable for production deployment.
Before You Begin
At first, you need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.
Now, install the KubeDB operator in your cluster following the steps here.
To keep things isolated, this tutorial uses a separate namespace called demo throughout this tutorial.
$ kubectl create namespace demo
namespace/demo created
$ kubectl get namespace
NAME STATUS AGE
demo Active 9s
Note: YAML files used in this tutorial are stored in here in GitHub repository kubedb/docs.
Create Topology Kafka Cluster
Here, we are going to create a TLS secured Kafka topology cluster in Kraft mode.
Create Issuer/ ClusterIssuer
At first, make sure you have cert-manager installed on your k8s for enabling TLS. KubeDB operator uses cert manager to inject certificates into kubernetes secret & uses them for secure SASL encrypted communication among kafka brokers and controllers. We are going to create an example Issuer that will be used throughout the duration of this tutorial to enable SSL/TLS in Kafka. Alternatively, you can follow this cert-manager tutorial to create your own Issuer.
- Start off by generating you CA certificates using openssl.
openssl req -newkey rsa:2048 -keyout ca.key -nodes -x509 -days 3650 -out ca.crt
- Now create a ca-secret using the certificate files you have just generated.
kubectl create secret tls kafka-ca \
--cert=ca.crt \
--key=ca.key \
--namespace=demo
Now, create an Issuer using the ca-secret you have just created. The YAML file looks like this:
apiVersion: cert-manager.io/v1
kind: Issuer
metadata:
name: kafka-ca-issuer
namespace: demo
spec:
ca:
secretName: kafka-ca
Apply the YAML file:
$ kubectl create -f https://github.com/kubedb/docs/raw/v2023.12.11/docs/examples/kafka/tls/kf-issuer.yaml
issuer.cert-manager.io/kafka-ca-issuer created
Provision TLS secure Kafka
For this demo, we are going to provision kafka version 3.3.2 with 3 controllers and 3 brokers. To learn more about Kafka CR, visit here. visit here to learn more about KafkaVersion CR.
apiVersion: kubedb.com/v1alpha2
kind: Kafka
metadata:
name: kafka-prod
namespace: demo
spec:
version: 3.3.2
enableSSL: true
tls:
issuerRef:
apiGroup: cert-manager.io
name: kafka-ca-issuer
kind: Issuer
topology:
broker:
replicas: 3
storage:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
storageClassName: standard
controller:
replicas: 3
storage:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
storageClassName: standard
storageType: Durable
terminationPolicy: DoNotTerminate
Let’s deploy the above example by the following command:
$ kubectl create -f https://github.com/kubedb/docs/raw/v2023.12.11/docs/examples/kafka/clustering/kf-topology.yaml
kafka.kubedb.com/kafka-prod created
Watch the bootstrap progress:
$ kubectl get kf -n demo -w
NAME TYPE VERSION STATUS AGE
kafka-prod kubedb.com/v1alpha2 3.3.2 Provisioning 6s
kafka-prod kubedb.com/v1alpha2 3.3.2 Provisioning 14s
kafka-prod kubedb.com/v1alpha2 3.3.2 Provisioning 50s
kafka-prod kubedb.com/v1alpha2 3.3.2 Ready 68s
Hence, the cluster is ready to use. Let’s check the k8s resources created by the operator on the deployment of Kafka CRO:
$ kubectl get all,secret,pvc -n demo -l 'app.kubernetes.io/instance=kafka-prod'
NAME READY STATUS RESTARTS AGE
pod/kafka-prod-broker-0 1/1 Running 0 4m10s
pod/kafka-prod-broker-1 1/1 Running 0 4m4s
pod/kafka-prod-broker-2 1/1 Running 0 3m57s
pod/kafka-prod-controller-0 1/1 Running 0 4m8s
pod/kafka-prod-controller-1 1/1 Running 2 (3m35s ago) 4m
pod/kafka-prod-controller-2 1/1 Running 0 3m53s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/kafka-prod-broker ClusterIP None <none> 9092/TCP,29092/TCP 4m14s
service/kafka-prod-controller ClusterIP None <none> 9093/TCP 4m14s
NAME READY AGE
statefulset.apps/kafka-prod-broker 3/3 4m10s
statefulset.apps/kafka-prod-controller 3/3 4m8s
NAME TYPE VERSION AGE
appbinding.appcatalog.appscode.com/kafka-prod kubedb.com/kafka 3.3.2 4m8s
NAME TYPE DATA AGE
secret/kafka-prod-admin-cred kubernetes.io/basic-auth 2 4m14s
secret/kafka-prod-broker-config Opaque 3 4m14s
secret/kafka-prod-client-cert kubernetes.io/tls 3 4m14s
secret/kafka-prod-controller-config Opaque 3 4m10s
secret/kafka-prod-keystore-cred Opaque 3 4m14s
secret/kafka-prod-server-cert kubernetes.io/tls 5 4m14s
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
persistentvolumeclaim/kafka-prod-data-kafka-prod-broker-0 Bound pvc-1ce9bf24-8d2d-4cae-9453-28df9f52ac44 1Gi RWO standard 4m10s
persistentvolumeclaim/kafka-prod-data-kafka-prod-broker-1 Bound pvc-5e2dc46b-0947-4de1-adb0-307fc881b2ba 1Gi RWO standard 4m4s
persistentvolumeclaim/kafka-prod-data-kafka-prod-broker-2 Bound pvc-b7ef2986-db7d-4089-95a2-474cd14c6282 1Gi RWO standard 3m57s
persistentvolumeclaim/kafka-prod-data-kafka-prod-controller-0 Bound pvc-8e3ae399-fb87-4906-91d8-3f5a09014d2a 1Gi RWO standard 4m8s
persistentvolumeclaim/kafka-prod-data-kafka-prod-controller-1 Bound pvc-faf53264-e125-430a-9a73-c2c73da1b97e 1Gi RWO standard 4m
persistentvolumeclaim/kafka-prod-data-kafka-prod-controller-2 Bound pvc-d962a03b-7af7-41ba-9d53-044e8ffa03f2 1Gi RWO standard 3m53s
Publish & Consume messages with Kafka
We will create a Kafka topic using kafka-topics.sh script which is provided by kafka container itself. We will use kafka console producer and kafka console consumer as clients for publishing messages to the topic and then consume those messages. Exec into one of the kafka broker pods in interactive mode first.
$ kubectl exec -it -n demo kafka-prod-broker-0 -- bash
root@kafka-prod-broker-0:~# pwd
/opt/kafka
You will find a file named clientauth.properties in the config directory. This file is generated by the operator which contains necessary authentication/authorization configurations that are required during publishing or subscribing messages to a kafka topic.
root@kafka-prod-broker-0:~# cat config/clientauth.properties
sasl.jaas.config=org.apache.kafka.common.security.plain.PlainLoginModule required username="admin" password="*************";
security.protocol=SASL_SSL
sasl.mechanism=PLAIN
ssl.truststore.location=/var/private/ssl/server.truststore.jks
ssl.truststore.password=***********
Now, we have to use a bootstrap server to perform operations in a kafka broker. For this demo, we are going to use the http endpoint of the headless service kafka-prod-broker as bootstrap server for publishing & consuming messages to kafka brokers. These endpoints are pointing to all the kafka broker pods. We will set an environment variable for the clientauth.properties filepath as well. At first, describe the service to get the http endpoints.
$ kubectl describe svc -n demo kafka-prod-broker
Name: kafka-prod-broker
Namespace: demo
Labels: app.kubernetes.io/component=database
app.kubernetes.io/instance=kafka-prod
app.kubernetes.io/managed-by=kubedb.com
app.kubernetes.io/name=kafkas.kubedb.com
Annotations: <none>
Selector: app.kubernetes.io/instance=kafka-prod,app.kubernetes.io/managed-by=kubedb.com,app.kubernetes.io/name=kafkas.kubedb.com,kubedb.com/role=broker
Type: ClusterIP
IP Family Policy: SingleStack
IP Families: IPv4
IP: None
IPs: None
Port: http 9092/TCP
TargetPort: http/TCP
Endpoints: 10.244.0.33:9092,10.244.0.37:9092,10.244.0.41:9092
Port: internal 29092/TCP
TargetPort: internal/TCP
Endpoints: 10.244.0.33:29092,10.244.0.37:29092,10.244.0.41:29092
Session Affinity: None
Events: <none>
Use the http endpoints and clientauth.properties file to set environment variables. These environment variables will be useful for handling console command operations easily.
root@kafka-prod-broker-0:~# export SERVER="10.244.0.100:9092,10.244.0.104:9092,10.244.0.108:9092"
root@kafka-prod-broker-0:~# export CLIENTAUTHCONFIG="$HOME/config/clientauth.properties"
Let’s describe the broker metadata for the quorum.
root@kafka-prod-broker-0:~# kafka-metadata-quorum.sh --command-config $CLIENTAUTHCONFIG --bootstrap-server localhost:9092 describe --status
ClusterId: 11ed-82ed-2a2abab96b3w
LeaderId: 2
LeaderEpoch: 15
HighWatermark: 1820
MaxFollowerLag: 0
MaxFollowerLagTimeMs: 159
CurrentVoters: [0,1,2]
CurrentObservers: [3,4,5]
It will show you important metadata information like clusterID, current leader ID, broker IDs which are participating in leader election voting and IDs of those brokers who are observers. It is important to mention that each broker is assigned a numeric ID which is called its broker ID. The ID is assigned sequentially with respect to the host pod name. In this case, The pods assigned broker IDs are as follows:
| Pods | Broker ID |
|---|---|
| kafka-prod-broker-0 | 3 |
| kafka-prod-broker-1 | 4 |
| kafka-prod-broker-2 | 5 |
Let’s create a topic named sample with 1 partitions and a replication factor of 1. Describe the topic once it’s created. You will see the leader ID for each partition and their replica IDs along with in-sync-replicas(ISR).
root@kafka-prod-broker-0:~# kafka-topics.sh --command-config $CLIENTAUTHCONFIG --create --topic sample --partitions 1 --replication-factor 1 --bootstrap-server localhost:9092
Created topic sample.
root@kafka-prod-broker-0:~# kafka-topics.sh --command-config $CLIENTAUTHCONFIG --describe --topic sample --bootstrap-server localhost:9092
Topic: sample TopicId: mqlupmBhQj6OQxxG9m51CA PartitionCount: 1 ReplicationFactor: 1 Configs: segment.bytes=1073741824
Topic: sample Partition: 0 Leader: 4 Replicas: 4 Isr: 4
Now, we are going to start a producer and a consumer for topic sample using console. Let’s use this current terminal for producing messages and open a new terminal for consuming messages. Let’s set the environment variables for bootstrap server and the configuration file in consumer terminal also.
From the topic description we can see that the leader partition for partition 0 is 4 that is kafka-prod-broker-1. If we produce messages to kafka-prod-broker-1 broker(brokerID=4) it will store those messages in partition 0. Let’s produce messages in the producer terminal and consume them from the consumer terminal.
root@kafka-prod-broker-1:~# kafka-console-producer.sh --producer.config $CLIENTAUTHCONFIG --topic sample --request-required-acks all --bootstrap-server localhost:9092
>hello
>hi
>this is a message from console producer client
>I hope it's received by console consumer
>
root@kafka-prod-broker-1:~# kafka-console-consumer.sh --consumer.config $CLIENTAUTHCONFIG --topic sample --from-beginning --bootstrap-server localhost:9092 --partition 0
hello
hi
this is a message from console producer client
I hope it's received by console consumer
Notice that, messages are coming to the consumer as you continue sending messages via producer. So, we have created a kafka topic and used kafka console producer and consumer to test message publishing and consuming successfully.
Cleaning Up
TO clean up the k8s resources created by this tutorial, run:
# standalone cluster
$ kubectl patch -n demo kf kafka-prod -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
$ kubectl delete kf -n demo kafka-prod
# multinode cluster
$ kubectl patch -n demo kf kafka-prod -p '{"spec":{"terminationPolicy":"WipeOut"}}' --type="merge"
$ kubectl delete kf -n demo kafka-prod
# delete namespace
$ kubectl delete namespace demo
Next Steps
- Deploy dedicated topology cluster for Apache Kafka
- Monitor your Kafka cluster with KubeDB using
out-of-the-boxPrometheus operator. - Detail concepts of Kafka object.
- Detail concepts of KafkaVersion object.
- Learn to use KubeDB managed Kafka objects using CLIs.
- Want to hack on KubeDB? Check our contribution guidelines.