Unable to query Kafka in Kubernetes deployment

Question

On a single Ubuntu 14.04 box

I've followed the same configuration as http://dojoblog.dellemc.com/dojo/deploy-kafka-cluster-kubernetes/

I use Kubernetes version v1.10.2 ( I also use apiVersion: apps/v1 in yml files. )

Basically I have setup a kubernetes service for kafka, and a kafka deployment using image wurstmeister/kafka . Zookeeper is working ok. Zookeeper and Kafka services are up. Kafka deployment is configured as per the blog : KAFKA_ADVERTISED_HOST_NAME = the kafa service cluster IP which is for me 10.106.84.132

deployment config :

....
 containers:
      - name: kafka
        image: wurstmeister/kafka
        ports:
        - containerPort: 9092
        env:
        - name: KAFKA_ADVERTISED_PORT
          value: "9092"
        - name: KAFKA_ADVERTISED_HOST_NAME
          value: 10.106.84.132
        - name: KAFKA_ZOOKEEPER_CONNECT
          value: zoo1:2181
        - name: KAFKA_BROKER_ID
          value: "1"
        - name: KAFKA_CREATE_TOPICS
          value: topic1:3:3

Then I test the kafka subscribe and publish from outside the kafka container on my host, but that fails as follow :

root@edmitchell-virtual-machine:~# kafkacat -b 10.106.84.132:9092 -t topic1

% Auto-selecting Consumer mode (use -P or -C to override)
% ERROR: Topic topic1 error: Broker: Leader not available

The best I could do overall was

I delete and recreate a kafka deployment with

• name: KAFKA_ADVERTISED_HOST_NAME value: localhost

I can then subscribe and publish but only from within the kafka container, it doesn't work from outside. If I change the value to anything else than localhost, nothing works.

Any idea ? It looks as if Kafka is not good to be used with Kubernetes ? maybe I should not deploy Kafka not using kubernetes..

many thanks ed

---

Thank you, I understand better now the nodeport function.

I still have the same issue :

root@fnature-virtual-machine:~/Zookeeper# kafkacat -b 192.168.198.160:32748 -t topic1 % Auto-selecting Consumer mode (use -P or -C to override) % ERROR: Topic topic1 error: Broker: Leader not available

I created the nodeport service as you said.

kafka-nodeport NodePort 10.111.234.104 9092:32748/TCP 27m

kafka-service LoadBalancer 10.106.84.132 9092:30351/TCP 1d

I also delete/create the kafka deployment with following env :

 KAFKA_ADVERTISED_PORT: 32748

 KAFKA_ADVERTISED_HOST_NAME:  192.168.198.160

  KAFKA_ZOOKEEPER_CONNECT:     zoo1:2181

  KAFKA_BROKER_ID:             1

  KAFKA_CREATE_TOPICS:         topic1:3:3

—

also if I run the following from inside the kafka container, I get similar error

"Leader not available". kafka-console-consumer.sh --bootstrap-server localhost:9092 --topic topic1 --from-beginning

if I create the kafka deployment with KAFKA_ADVERTISED_HOST_NAME: localhost , then above command works inside the kafka container

and 192.168.198.160 is the ip of default interface ens33 in my Ubuntu VM

I can't seem to find any logs for kafka

Answer 1

Kafka broker registers an address to zookeeper via KAFKA_ADVERTISED_HOST_NAME . However, this address is a kubernetes cluster ip (10.106.84.132), which is only reachable within Kubernetes cluster. So a client outside the cluster can not reach Kafka broker using this address.

To resolve this problem, you can expose kafka service to a public ip, either through NodePort or LoadBalancer . For example, run kubectl expose svc $YOUR_KAFKA_SERVICE_NAME --name=kafka-nodeport --type=NodePort , then lookup what nodeport is exposed: kubectl get svc kafka-nodeport -o yaml | grep nodePort kubectl get svc kafka-nodeport -o yaml | grep nodePort . In this example, kafka broker will be accessible via this address: $KUBERNETES_NODE_IP : $NODEPORT .

Answer 2

in k8s, deployment kafka.yaml

env:
- name: KAFKA_BROKER_ID
  value: "1"
- name: KAFKA_CREATE_TOPICS
  value: "test:1:1"
- name: KAFKA_ZOOKEEPER_CONNECT
  value: "zookeeper:2181"
- name: KAFKA_ADVERTISED_LISTENERS
  value: "INSIDE://:9092,OUTSIDE://kafka-com:30322"
- name: KAFKA_LISTENERS
  value: "INSIDE://:9092,OUTSIDE://:30322"
- name: KAFKA_LISTENER_SECURITY_PROTOCOL_MAP
  value: "INSIDE:PLAINTEXT,OUTSIDE:PLAINTEXT"
- name: KAFKA_INTER_BROKER_LISTENER_NAME
  value: "INSIDE" 

kafka service,the external service invocation address, or traefik proxy address

---
kind: Service
apiVersion: v1
metadata:
  name: kafka-com
  namespace: dev
  labels:
    k8s-app: kafka
spec:
  selector:
    k8s-app: kafka
  ports:
  - port: 9092
    name: innerport
    targetPort: 9092
    protocol: TCP
  - port: 30322
    name: outport 
    targetPort: 30322
    protocol: TCP
    nodePort: 30322
  type: NodePort

Ensure that Kafka external port and nodePort are consistent,Other services call kafka-com:30322, my blog write this config_kafka_in_kubernetes , hope to help U !