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The Apache Kafka event receiver subscribes to a user-defined topic on a user-configured Kafka broker. Then the messages published to that topic are received by the Kafka receiver and forwarded to the WSO2 product engine. This feature is donated by Andres Gomez Ferrer. For more information, see Apache Kafka documentation.

Prerequisites

Set up the below prerequisites to start configuring an Apache Kafka event receiver.

  1. Download Apache Kafka server
  2. Copy the following client JAR files from <KAFKA_HOME>/lib/ directory  to <PRODUCT_HOME>/repository/components/lib/ directory.

    • kafka_2.10-0.8.1.jar
    • zkclient-0.3.jar
    • scala-library-2.10.1.jar
    • zookeeper-3.3.4.jar
    • kafka-clients-0.8.2.1
    • metrics-core-2.2.0

    If you are using Kafka_2.11-0.10.0.0, you need to download this jar and save it in the <PRODUCT_HOME>/repository/components/lib/ directory.

  3. Start the Apache Kafka server.

Creating an Kafka  event receiver 

For instructions on creating an  Apache Kafka event receiver, see Configuring Event Receivers .  

Configuring adapter properties

Specify the Adapter Properties , when creating an Apache Kafka  event receiver using the management console as shown below.

Apache Kafka input event adapter

After entering the above adapter properties, select the  Event Stream  to which you want to map the incoming events, and the  Message Format  which you want to apply on the receiving events. Also, click  Advanced  to define custom input mappings based on the  Message Format  you selected. For more information on custom input mapping types, see  Input Mapping Types .

You can also d efine the respective adapter properties of the event receiver based on the transport type within the  <from>  element of the event receiver configuration in the <PRODUCT_HOME>/repository/deployment/server/eventreceivers/ directory as follows.

<eventReceiver name="KafkaInputEventAdpater" statistics="disable" trace="disable" xmlns="http://wso2.org/carbon/eventreceiver">
    <from eventAdapterType="kafka">
        <property name="topic">test_topic</property>
        <property name="zookeeper.connect">127.0.0.1</property>
        <property name="threads">4</property>
        <property name="optional.configuration">zk.sessiontimeout.ms:6000</property>
        <property name="group.id">groupid</property>
        <property name="events.duplicated.in.cluster">false</property>
    </from>
    .....................
</eventReceiver>

The above adapter properties are described below.

Adapter Property
Description
Configuration file propertyExample

Server Zookeeper IP

IP address of the Zookeeper Server

zookeeper.connect
127.0.0.1

Group ID Kafka

Kafka consumer group id which uniquely identifies a set of consumers within the same consumer group

group.id
groupid

Threads

Number of consumer threads

threads
4
Optional Configuration Properties

Valid property and value pairs to denote o ptional configuration properties for Apache Kafka. (E.g. "property1: value1, property2: value2")

For more information on Axis2 JMS properties, go to Apache Kafka Documentation.

optional.configurationzk.sessiontimeout.ms:6000
Topic Kafka Name of the Kafka topic to which, input messages are published
topic
test_topic
Is events duplicated in cluster In a cluster whether the same event can reach two receiver nodes
events.duplicated.in.cluster
true/false

Related samples

For more information on kafka event receiver type, see the following sample in WSO2 CEP Documentation.

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