Setting up Kafka Connect with Debezium Connectors: Importance of Database History Parameters

If you're working with databases, you've probably heard of Kafka, Kafka Connect, and connectors. In a nutshell, Kafka is a distributed streaming platform that allows you to publish and subscribe to streams of records, while Kafka Connect is a framework that simplifies the process of getting data into and out of Kafka. Connectors are plugins that let you connect to various data sources and sync them with Kafka.

One popular set of connectors for Kafka are the Debezium connectors. These connectors are specifically designed for change data capture (CDC) scenarios, which involve capturing changes in a database and publishing them to Kafka topics. The Debezium connectors are available for various databases, including MySQL, PostgreSQL, Oracle, and SQL Server.

However, when setting up the Debezium connectors, there's an important consideration to keep in mind: the configuration of the Kafka topic used for storing the history of database changes. This topic is set using the database.history.kafka.topic parameter, and it's critical that this topic has infinite retention and a single partition. https://debezium.io/documentation/reference/1.9/install.html#_configuring_debezium_topics
Starting 2.0 debezium changed the paramater name to schema.history.internal.kafka.topic so if you are reading this wondering why you don't have that parameter you might be implementing the 2.x version of the connector

apiVersion: kafka.strimzi.io/v1beta2
kind: KafkaConnector
metadata:
  name: sql-connector-001
  labels:
    strimzi.io/cluster: debezium-connect-cluster
spec:
  class: io.debezium.connector.sqlserver.SqlServerConnector
  tasksMax: 1
  config:
    database.history.kafka.topic: schema-changes-topic
    ...

It's worth noting that Confluent Kafka, the most popular distribution of Kafka, sets its topics with only one week of retention by default. This means that if you're using Confluent Kafka, you'll need to override this default behavior for the history topic.

If you don't set the retention policy for the history topic correctly, you may run into issues with the Debezium connector not working properly. One common error message is "The db history topic or its content is fully or partially missing. Please check the database history topic configuration and re-execute the snapshot."

If you encounter this error, you'll need to take corrective action, which may involve nuking the topics, setting proper configurations, and starting from scratch. Alternatively, you could rename the connector to another name, which is a temporary fix that will only last another week.

In summary, when setting up Kafka Connect with Debezium Connectors, it's important to pay close attention to the configuration of the history topic. Make sure that it has infinite retention and a single partition to avoid issues with the Debezium connector not working properly. Open source no-code tools like Kafka Connect make it easier than ever to build a scalable, reliable, and distributed data pipeline. However, it's essential to be careful about configuring our connectors, which can often go wrong without us realizing it. By setting the right configuration parameters for the database history topic, we can ensure that our Kafka Connect pipeline runs smoothly and without any hiccups. I hope this blog post helps you avoid any potential issues and that you are reading this before you release your connectors to production.