Working with Messages in Kafka

The publishMessage operation allows you to publish messages to Kafka brokers using Kafka topics.

publishMessages

<kafkaTransport.publishMessages>
	<topic>topicName</topic>
</kafkaTransport.publishMessages>

Properties

topic: The name of the topic.

Sample scenario

Following is a sample scenario that demonstrates how to send messages to a Kafka broker using Kafka topics.

Prerequisites

Download and install Apache Kafka. For more information, see Apache Kafka documentation.
Copy the following client libraries from the <KAFKA_HOME>/lib directory to the <ESB_HOME>/repository/components/lib directory.
- kafka_2.9.2-0.8.1.1.jar
- scala-library-2.9.2.jar
- zkclient-0.3.jar
- zookeeper-3.3.4.jar
- metrics-core-2.2.0.jar
Run the following command to start the ZooKeeper server:
```
bin/zookeeper-server-start.sh config/zookeeper.properties
```
You will see the following log:
Run the following command to start the Kafka server:
```
bin/kafka-server-start.sh config/server.properties
```
You will see the following log:

Building the sample

Following is a sample proxy service that illustrates how you can connect to a Kakfa broker with the init operation and use the publishMessages operation to publish the messages with the topic.

<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="KafkaTransport"
       transports="https http"
       startOnLoad="true"
       trace="disable">
   <description/>
   <target>
      <inSequence>
         <kafkaTransport.init>
            <brokerList>localhost:9092</brokerList>
         </kafkaTransport.init>
         <kafkaTransport.publishMessages>
            <topic>test</topic>
         </kafkaTransport.publishMessages>
      </inSequence>
   </target>
</proxy>

Following is a sample client(JMeter) screen that displays how to send a message:

Analyzing the output

Run the following command to verify the messages:
```
bin/kafka-console-consumer.sh --zookeeper localhost:2181 --topic test --from-beginning
```
You will see the following message content:

<name>sample</name>

This demonstrates that the Kafka connector publishes messages to Kafka brokers.