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Kafka Connect

Kafka connect is an open source component for easily integrate external systems with Kafka. It works with any Kafka product like IBM Event Streams, Srimzi, AMQ Streams. It uses the concepts of source and sink connectors to ingest or deliver data to / from Kafka topics.

Kafka component

The general concepts are detailed in the IBM Event streams product documentation, and Robin Moffatt’s video. Here is a quick summary:

  • Connector represents a logical job to move data from / to kafka to / from external systems. A lot of existing connectors can be reused, or you can implement your own.
  • Workers are JVMs running the connector. For production deployment workers run in cluster or “distributed mode”, and leverage the Kafka consumer group management protocol to scale task horizontally.
  • Tasks: each worker coordinates a set of tasks to copy data. In distributed mode, task states are saved in Kafka topics. They can be started, stopped at any time to support resilience, and scalable data pipeline.
  • REST API to configure the connectors and monitors the tasks.

The following figure illustrates a classical ‘distributed’ deployment of a Kafka Connect cluster. Workers are the running processes to execute connectors and tasks. Tasks are threads in a JVM. For fault tolerance and offset management, Kafka connect uses Kafka topics (suffix name as -offsets, -config, -status) When a connector is first submitted to the cluster, the workers rebalance the full set of connectors in the cluster with their tasks so that each worker has approximately the same amount of work. 

Connectors and tasks
  • Connector and tasks are not guaranteed to run on the same instance in the cluster, especially if you have multiple tasks and multiple instances in your cluster.
  • Connector coordinates data streaming by managing tasks
  • The connector may be configured to add Converters (code used to translate data between Connect and the system sending or receiving data), and Transforms: simple logic to alter each message produced by or sent to a connector.

Connector keeps state into three topics, which may be created when the connectors start are:

  • connect-configs: This topic stores the connector and task configurations.
  • connect-offsets: This topic stores offsets for Kafka Connect.
  • connect-status: This topic stores status updates of connectors and tasks.


  • Copy vast quantity of data from source to kafka: work at the datasource level. So when the source is a database, it uses JDBC API for example.
  • Support streaming and batch.
  • Scale from standalone, mono connector approach to start small, to run in parallel on distributed cluster.
  • Copy data, externalizing transformation in other framework.
  • Kafka Connect defines three models: data model, worker model and connector model.

Fault tolerance

When a worker fails:

fault 1

Tasks allocated in the failed worker are reallocated to existing workers, and the task’s state, read offsets, source record mapping to offset are reloaded from the different topics.

fault 2

Both figure above are illustrating a MongoDB sink connector.


The Kafka connect framework fits well into a kubernetes deployment. In 2021 we have different options for that deployment: the Strimzi Kafka connect operator, IBM Event Streams Connector, Red Hat AMQ Streams (2021.Q3) connector or one of the Confluent connector.

IBM Event Streams Cloud Pak for Integration

If you are using IBM Event Streams 2021.x on Cloud Pak for Integration, the connectors setup is part of the user admin console toolbox:

Event Streams connector

Deploying connectors against an IBM Event Streams cluster, you need to have a Kafka user with Manager role, to be able to create topic, produce and consume messages for all topics.

As an extendable framework, Kafka Connect, can have new connector plugins. To deploy new connector, you need to use the kafka docker image which needs to be updated with the connector jars and redeployed to kubernetes cluster or to other environment. With IBM Event Streams on Openshift, the toolbox includes a kafka connect environment packaging, that defines a Dockerfile and configuration files to build your own image with the connectors jar files you need. The configuration files defines the properties to connect to Event Streams kafka brokers using API keys and SASL.

The following public IBM messaging github account includes supported, open sourced, connectors (search for connector).

Here is the list of supported connectors for IBM Event Streams.

Event Stream Kafka connector use custom resource definition defined by Strimzi. So configuration for Strimzi works for Event Streams.

Normally you define one Kafka connect cluster, with a custom docker image which has all the necessary jars file for any connector you want to use. Then you configure each connector so they can start processing events or producing events. A Kafka connect cluster is identified with a and then it saves its states in topics. The example below are for the configuration in cluster, also named distributed.

config: connect-cluster connect-cluster-offsets connect-cluster-configs connect-cluster-status

This gitops repository includes a MQ Source connector deploy to push message to Kafka. It uses ArgoCD to maintain states of Kafka Cluster, topics, users, and Kafka connector.

Once the connector pods are running we need to start the connector tasks.


KafkaConnector resources allow you to create and manage connector instances for Kafka Connect in a Kubernetes-native way. To manage connectors, you can use the Kafka Connect REST API, or use KafkaConnector custom resources. In case of GitOps methodology we will define connector cluster and connector instance as yamls. Connector configuration is passed to Kafka Connect as part of an HTTP request and stored within Kafka itself.

Further Readings