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Kafka Access (Enterprise Edition)

Benerator can read from and write to Kafka queues.

Basic configuration

The basic configuration elements required for any kind of Kafka connector are

Name Description
id the internal id by which the Kafka connector can be accessed in Benerator
bootstrap.servers See the original Kafka Documentation
topic The name of the Kafka queue to connect to
format The message format used in this queue. Currently, only 'json' is supported

Depending on the system you want to connect to, you might need to provide Advanced configuration.


For exporting data, a <kafka-exporter> is used:

    <kafka-exporter id='exporter' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json'/>
    <generate type='person' count='10' consumer='exporter'>
        <attribute name="name" pattern="Alice|Bob|Charly"/>
        <attribute name="age" type="int" min="18" max="67"/>


For importing data, a <kafka-importer> is used:

    <kafka-importer id='importer' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json'/>
    <iterate source='importer' type='person' count='10' consumer='ConsoleExporter'/>

Advanced configuration

Kafka properties

Benerator supports all configuration properties of Kafka 2.8. For an in-depth explanation of these, please have a look at the Kafka Documentation.


By default, Benerator uses UTF-8 encoding to read and write JSON.

If you need to use another encoding like UTF-16, specify it as encoding parameter:

<kafka-exporter id='exporter' bootstrap.servers='localhost:9094' topic='kafka-demo' 
    format='json' encoding='UTF-16'/>


By default, a kafka-importer runs forever. When using the idle.timeout.seconds property, it can be configured to stop automatically after a certain number of seconds without message reception.


When connecting to a topic, a client declares which group it belongs to and the group is assigned a message offset, which is stored on the server. When messages with a higher offset exist in the queue or are sent to it, the Kafka server sends them to the client and increases the saved offset.

The client declares its group using the setting, which Benerator sets to default, if not provided explicitly.

When a client reconnects, the Kafka server remembers the client group's offset and delivers the new messages.

This is the good case. In some situations, this method has issues:

  • New client group

  • Topic was deleted and recreated

  • messages have been deleted

  • You name it

Therefore, a client must declare an offset reset strategy (auto.offset.reset) to be applied in such a case. The setting can have the following values

  • earliest: automatically reset the offset to the earliest offset

  • latest: automatically reset the offset to the latest offset

  • none: throw exception to the consumer if no previous offset is found for the consumer's group


In order to tell a Kafka exporter which data to use as key to the exported message, specify the attribute name as key.attribute, for example using an order priority as key:

    <kafka-exporter id='exporter' bootstrap.servers='localhost:9094' key.attribute='priority' topic='kafka-demo' format='json'/>
    <generate type='order' count='100' consumer='exporter'>
        <attribute name='priority' type='string' script='(high|medium|low)'/>
        <attribute name='orderId' type='long' distribution='increment'/>
        <attribute name='productId' type='long' min='1' max='300'/>

key.serializer and key.deserializer

For de/serializing of message keys, Kafka provides different classes, each defined in Kafka's package org.apache.kafka.common.serialization. For sending messages a serializer is used, for receiving messages a deserializer.

By default, Benerator uses Kafka's StringSerializer and StringDeserializer.

If necessary, you can use other de/serializer classes, specifying the key.serializer or key.deserializer setting with one of these:

  • org.apache.kafka.common.serialization.ByteArraySerializer or ByteArrayDeserializer

  • org.apache.kafka.common.serialization.BytesSerializer or BytesSerializer

  • org.apache.kafka.common.serialization.DoubleSerializer or DoubleDeserializer

  • org.apache.kafka.common.serialization.FloatSerializer or FloatDeserializer

  • org.apache.kafka.common.serialization.IntegerSerializer or IntegerDeserializer

  • org.apache.kafka.common.serialization.LongSerializer or LongDeserializer

  • org.apache.kafka.common.serialization.ShortSerializer or ShortDeserializer

  • org.apache.kafka.common.serialization.StringSerializer or StringDeserializer

Alternatively, you can implement and provide your own de/serializer.


Kafka commits its messages received. For faster read access to a Kafka queue, you can use the Kafka-Settings and to combine a larger number of objects in one transaction, thus reducing transaction overhead.


<kafka-importer id='importer' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json''true''5000'/>

For a better match with Benerator's pageSize approach, you can use this in a Kafka-Importer too, e.g. for committing messages in groups of 10,000:

<kafka-importer id='importer' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json' 

Encryption and Authentication

Ask your Kafka administrator on details how to configure secure access. All settings you might need are available in the XML format, your configuration could look like this:

<kafka-importer id='importer' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json'

If the Benerator file is shared, but your access individual, then remember that you can hide your password from the XML setup file by using the properties file mechanism in your user folder, see '<setting> and Benerator identifiers':

Local file


Shared file benerator.xml:

<include uri=""/>
<kafka-importer id='importer' bootstrap.servers='localhost:9094' topic='kafka-demo' format='json'

AVRO Support

Since Release 3.0.0, Benerator supports AVRO.
In order to use it, set the following attributes of the <Kafka-exporter> or <Kafka-importer> element:

  • format: Set this to AVRO.

  • schema.url: The URL of the AVRO schema file. Attention: The current implementation does not support https. This will be resolved in a future release. Until then, pleas download the schema file, save it in your project folder and make the schema.url point to the saved file.