Apache Kafka Connect is a tool for integrating Kafka with external systems such as databases, key-value stores, and file systems. It provides a scalable and fault-tolerant way to stream data between Kafka and other systems using connectors.
Connectors in Kafka Connect can be either source connectors, which pull data from external systems into Kafka, or sink connectors, which push data from Kafka into external systems. Kafka Connect also supports custom connectors for specific use cases.
While Kafka Connect provides a variety of built-in connectors, there are scenarios where custom connectors are needed. These scenarios might include:
Creating a custom Kafka Connect plugin involves several steps. Here is a high-level overview:
SourceConnector
or SinkConnector
interface depending on whether you are building a source or sink connector.AbstractConfig
to specify the configuration parameters for your connector.SourceTask
or SinkTask
, responsible for the actual data transfer.Below is an example of a custom Kafka Connect source connector that reads data from a hypothetical data source.
import org.apache.kafka.connect.source.SourceConnector;
import org.apache.kafka.connect.source.SourceTask;
import org.apache.kafka.connect.connector.Task;
import org.apache.kafka.connect.connector.Connector;
import org.apache.kafka.common.config.ConfigDef;
import org.apache.kafka.connect.connector.ConnectorContext;
import org.apache.kafka.connect.source.SourceRecord;
import java.util.List;
import java.util.Map;
public class CustomSourceConnector extends SourceConnector {
private String configValue;
@Override
public void start(Map props) {
configValue = props.get("config.key");
}
@Override
public Class extends Task> taskClass() {
return CustomSourceTask.class;
}
@Override
public List
In this example, CustomSourceConnector
is the connector class that defines configuration and tasks, while CustomSourceTask
implements the logic for polling data from the source.
Once your custom connector and task classes are implemented, package them into a JAR file. This JAR file needs to be placed in the Kafka Connect plugins directory on the Kafka Connect worker nodes.
To package your plugin, use Maven or Gradle. For Maven, your pom.xml
should include the necessary dependencies and configuration for building the JAR.
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/POM/4.0.0">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>custom-connect-plugin</artifactId>
<version>1.0</version>>
<packaging>jar</packaging>
<dependencies>
<dependency>
<groupId>org.apache.kafka</groupId>
<artifactId>kafka-connect-api</artifactId>
<version>3.1.0</version>
</dependency>
</dependencies>
After packaging, copy the JAR file to the Kafka Connect plugins directory (typically specified by the plugin.path
configuration in connect-distributed.properties
or connect-standalone.properties
).
To use your custom connector, create a configuration file and specify the connector class, tasks, and any required configuration properties.
name=custom-source-connector
connector.class=com.example.CustomSourceConnector
tasks.max=1
config.key=some_value
Load this configuration file into Kafka Connect using the REST API or by placing it in the Kafka Connect configuration directory. Start or restart Kafka Connect to pick up the new plugin.