How to configure Debezium to use specific column as Kafka message key?

Question

By default, Debezium uses the primary key of the table as a message key. For example, if you have a table

create table users
(
    id            bigint auto_increment primary key,
    department_id bigint
);

with data

+----+----------------+
| id | department_id  |
+----+----------------+
|  5 |              1 |
|  6 |              1 |
|  7 |              2 |
+----+----------------+

Debezium will produce the following Kafka messages:

Key: {"id": 5} Value: {"id": 5, "department_id": 1}
Key: {"id": 6} Value: {"id": 6, "department_id": 1}
Key: {"id": 7} Value: {"id": 7, "department_id": 2}

The question is how to configure Debezium to use department_id or any other column as Kafka message key?

Answer 1

There is the message.key.columns parameter for this. In your connector's configuration, you should set it like this:

{
  "name": "my-connector",
  "config": {
    "connector.class": "io.debezium.connector.mysql.MySqlConnector",
    "tasks.max": "1",
    "database.hostname": "mysql",
    "database.port": "3306",
    "database.whitelist": "my_database",
    ...
    "message.key.columns": "my_database.users:department_id"
  }
}

This parameter is supported by all the relational Debezium connectors.

You can find more information here:

https://debezium.io/blog/2019/09/26/debezium-0-10-0-cr2-released/ https://debezium.io/documentation/reference/1.0/assemblies/cdc-mysql-connector/as_deploy-the-mysql-connector.html#mysql-connector-configuration-properties_debezium