Set up Kafka extension

• Install Kafka using helm

• Enabling Kafka extension

• Configuring the extension and Kafka

• End-to-end testing

Assumptions And Prerequisites

This guide assumes that:

• You have a Microsoft Azure account with an active subscription. If you don’t, create a new account for free.

• You have installed az, the Microsoft Azure command-line interface (CLI). In case you haven’t, install it using these instructions.

• kubectl v1.29.x

• Helm v3.x

• AKS cluster with Kubernetes API version 1.25 - 1.28.x

• PV provisioner support in the underlying infrastructure

• HiveMQ v.4.2x.x broker cluster installed to namespace hivemq using hivemq/hivemq-operator Helm chart

• You have installed mqtt-cli, the HiveMQ MQTT command-line interface (CLI).

Install Kafka using helm

1. Create a namespace for Kafka and switch the context to it:

   kubectl create namespace kafka; 
   kubectl config set-context --current --namespace=kafka 

2. Add the repository for the Kafka Helm chart to your package manager.

   helm repo add bitnami https://charts.bitnami.com/bitnami
   helm repo update

3. Deploy the Kafka server using the Helm chart. The below command deploys Kafka with 2 brokers (replicas).

   helm upgrade --install kafka bitnami/kafka --set replicaCount=2 

   1. If everything is correct, then

      1. Kafka can be accessed by consumers via port 9092 on the following DNS name from within your cluster:

         kafka.kafka.svc.cluster.local

      2. The CLIENT listener for Kafka client connections from within your cluster has been configured with the following security settings:

         • SASL authentication

      3. To connect a client to your Kafka:

         1. username="user1"

         2. To get the password execute the command below:

            kubectl get secret kafka-user-passwords --namespace kafka \
              -o jsonpath='{.data.client-passwords}' | base64 -d | cut -d , -f 1;

Enabling Kafka extension, Configuring the extension and Kafka

1. HiveMQ Enterprise Extension For Kafka requires a separate license file, e.g. kafka-license.elic, in the $HIVEMQ_HOME/license directory. You can skip this step. If you skip this step, then the kafka-extension will start in trial mode, limited to 5h, and will be automatically disabled by the HiveMQ broker after 5h. To add the kafka-license.elic along with the hivemq-license.lic, create a new configmap hivemq-license including all desired license files:

   kubectl create configmap hivemq-license \
     --from-file hivemq-licesen.lic \
     --from-file kafka-license.elic

2. Edit the values.yaml file of the hivemq-operator, section hivemq.configMaps. Update this:

     configMaps: []
     # ConfigMaps to mount to the HiveMQ pods. These can be mounted to existing directories without shadowing the folder contents as well.
     #- name: hivemq-license
     #  path: /opt/hivemq/license

   To this:

     configMaps: 
       - name: hivemq-license
         path: /opt/hivemq/license

   This will mount the content of the configMap hivemq-license to the directory /opt/hivemq/license of the hivemq-broker pods.

3. HiveMQ Enterprise Extension For Kafka is preinstalled with HiveMQ so once you enable it, it will look for its configuration file. You must prepare this file before enabling the extension. If you skip this step, the extension will not find its configuration file and will not load any configuration.

4. Prepare a simple configuration file for kafka-extension as in the example below.

   • this example configuration will map all incoming MQTT publish packets to the topic “test” in Kafka; and will map the topic “test” in Kafka to the topic “test-test” in the HiveMQ broker

   • Use your password in <password>here_is_your_password</password>, that you successfully retrieved with this command a few steps ago:

     kubectl get secret kafka-user-passwords --namespace kafka \
       -o jsonpath='{.data.client-passwords}' | base64 -d | cut -d , -f 1;

   • Here is the file:

<?xml version="1.0" encoding="UTF-8" ?>
<kafka-configuration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                     xsi:noNamespaceSchemaLocation="config.xsd">
    <kafka-clusters>
        <kafka-cluster>
            <id>cluster01</id>
            <bootstrap-servers>kafka.kafka.svc.cluster.local:9092</bootstrap-servers>
            <authentication>
                <scram-sha256>
                    <username>user1</username>
                    <password>here_is_your_password</password>
                </scram-sha256>
            </authentication>
        </kafka-cluster>
    </kafka-clusters>

    <mqtt-to-kafka-mappings>
        <mqtt-to-kafka-mapping>
            <id>mapping01</id>
            <cluster-id>cluster01</cluster-id>
            <mqtt-topic-filters>
                <mqtt-topic-filter>#</mqtt-topic-filter>
            </mqtt-topic-filters>
            <kafka-topic>test</kafka-topic>
        </mqtt-to-kafka-mapping>
    </mqtt-to-kafka-mappings>

    <kafka-to-mqtt-mappings>
        <kafka-to-mqtt-mapping>
            <id>mapping02</id>
            <cluster-id>cluster01</cluster-id>
            <kafka-topics>
                <kafka-topic>test</kafka-topic>
                <kafka-topic-pattern>test-(.)*</kafka-topic-pattern>
            </kafka-topics>
        </kafka-to-mqtt-mapping>
    </kafka-to-mqtt-mappings>
</kafka-configuration>

3. Create a new configMap kafka-config from the config.xml:

   kubectl create configmap kafka-config --from-file config.xml

4. Edit values.yaml file of hivemq-operator and update section hivemq.extensions, having name: hivemq-kafka-extension
   Update this:

     extensions:
       - name: hivemq-kafka-extension
         extensionUri: preinstalled
         enabled: false

   To this:

   extensions:
       - name: hivemq-kafka-extension
         extensionUri: preinstalled
         enabled: true
         configMap: kafka-config
         initialization: |
           # Fixes the location of the config.xml file
           [[ ! -f conf/config.xml ]] &&
           [[ -f /conf-override/extensions/hivemq-kafka-extension/config.xml ]] &&
           ln -s /conf-override/extensions/hivemq-kafka-extension/config.xml conf/config.xml

5. Re-deploy hivemq-operator with updated values.yaml

   helm upgrade hivemq --install hivemq/hivemq-operator --values my-hivemq-values.yaml --namespace hivemq

6. If everything is correct,

   1. The HiveMQ log contains info about using the correct license:

      kubectl logs deployment/hivemq | grep 'Using valid'

      INFO  - Using valid Enterprise Edition CPU license (hivemq-license.lic) issued to HiveMQ - Internal for max 9999 CPU cores, valid until 2024-03-31.
      INFO  - Using valid license (kafka-license.elic) for enterprise extension with name "HiveMQ Enterprise Extension for Kafka", valid until 2024-03-31.

   2. The HiveMQ log contains info about successful Kafka connection:

      kubectl logs deployments/hivemq -f | grep -i kafka

      INFO  - Starting extension with id "hivemq-kafka-extension" at /opt/hivemq/extensions/hivemq-kafka-extension
      INFO  - No mqtt-to-kafka transformers were found. No mqtt-to-kafka transformers are started.
      INFO  - Started mqtt-to-kafka mapping "mapping01" with MQTT topics [#] and Kafka topic "test" for Kafka Cluster "cluster01"
      INFO  - No kafka-to-mqtt transformers were found. No kafka kafka-to-mqtt transformers are started.
      INFO  - Started kafka-to-mqtt mapping "mapping02" with kafka topic: [test] and kafka pattern: [test-(.)*] for Kafka Cluster "cluster01" (poll duration: 100 ms).
      INFO  - Extension "HiveMQ Enterprise Extension for Kafka" version 4.24.0 started successfully.
      INFO  - Subscribing kafka-to-mqtt topic-mapping with id mapping02 to kafka pattern (test-(.)*|\Qtest\E)

   3. Kafka dashboard is visible in the HiveMQ Control Center:
      

      

End-to-end testing

1. Subscribe a reference mqtt client to the topic “test”, output show the topic name and message:

   mqtt subscribe --topic '#' --host $hivemqhost --port 1883 -q 1 --showTopics

   Do not close this terminal session!

2. From a different terminal session, publish a message to the topic “test”:

   mqtt publish --topic test --message Hello --host $hivemqhost --port 1883 -q 1

3. If everything is correct, the subscriber will indefinitely receive the message we published:

   mqtt subscribe --topic '#' --host $hivemqhost --port 1883 -q 1 --showTopics
   
   test: Hello
   test: Hello
   test: Hello
   test: Hello
   test: Hello
   test: Hello
   test: Hello
   test: Hello
   test: Hello

   You can stop this by terminating the execution of the command by pressing Ctrl+C.
   To gain extra points for this training, explain, why the message is received indefinitely rather than once.

If everything is correct, the Kafka Dashboard in the HiveMQ Control Center shows incoming and outgoing Kafka messaging: