Replicate data with Kafka (Confluent) and Debezium

Neon's logical replication feature allows you to replicate data from your Neon Postgres database to external destinations.

Confluent Cloud is a fully managed, cloud-native real-time data streaming service, built on Apache Kafka. It allows you to stream data from various sources, including Postgres, and build apps that consume messages from an Apache Kafka cluster.

In this guide, you will learn how to stream data from a Neon Postgres database to a Kafka cluster in Confluent Cloud. You will use the PostgreSQL CDC Source Connector (Debezium) for Confluent Cloud to read Change Data Capture (CDC) events from the Write-Ahead Log (WAL) of your Neon database in real-time. The connector will write events to a Kafka stream and auto-generate a Kafka topic. The connector performs an initial snapshot of the table and then streams any future change events.

Prerequisites

• A Confluent Cloud account
• A Neon account

Enable logical replication in Neon

To enable logical replication in Neon:

1. Select your project in the Neon Console.
2. On the Neon Dashboard, select Project settings.
3. Select Beta.
4. Click Enable to enable logical replication.

You can verify that logical replication is enabled by running the following query from the the Neon SQL Editor:

SHOW wal_level;
 wal_level 
-----------
 logical

Create a publication

In this example, we'll create a publication for a users table in the public schema of your Neon database.

1. Create the users table in your Neon database. You can do this via the Neon SQL Editor or by connecting to your Neon database from an SQL client such as psql.

   CREATE TABLE users (
     id SERIAL PRIMARY KEY,
     username VARCHAR(50) NOT NULL,
     email VARCHAR(100) NOT NULL
   );

2. Create a publication for the users table:

   CREATE PUBLICATION users_publication FOR TABLE users;

This command creates a publication, named users_publication, which will include all changes to the users table in your replication stream.

Create a Postgres role for replication

It is recommended that you create a dedicated Postgres role for replicating data. The role must have the REPLICATION privilege. The default Postgres role created with your Neon project and roles created using the Neon Console, CLI, or API are granted membership in the neon_superuser role, which has the required REPLICATION privilege.

Grant schema access to your Postgres role

If your replication role does not own the schemas and tables you are replicating from, make sure to grant access. Run these commands for each schema:

GRANT USAGE ON SCHEMA <schema_name> TO <role_name>;
GRANT SELECT ON ALL TABLES IN SCHEMA <schema_name> TO <role_name>;
ALTER DEFAULT PRIVILEGES IN SCHEMA <schema_name> GRANT SELECT ON TABLES TO <role_name>;

Granting SELECT ON ALL TABLES IN SCHEMA instead of naming the specific tables avoids having to add privileges later if you add tables to your publication.

Create a replication slot

The Debezium connector requires a dedicated replication slot. Only one source should be configured to use this replication slot.

To create a replication slot called debezium, run the following command on your database using your replication role:

SELECT pg_create_logical_replication_slot('debezium', 'pgoutput');

• debezium is the name assigned to the replication slot. You will need to provide the slot name when you set up your source connector in Confluent.
• pgoutput is the logical decoder plugin used in this example. Neon supports both pgoutput and wal2json decoder plugins.

Set up a Kafka cluster in Confluent Cloud

1. Sign in to Confluent Cloud at https://confluent.cloud.
2. Click Add cluster.
3. On the Create cluster page, for the Basic cluster, select Begin configuration.
4. On the Region/zones page, choose a cloud provider, a region, and select a single availability zone.
5. Select Continue.
6. Specify your payment details. You can select Skip payment for now if you're just trying out the setup.
7. Specify a cluster name, review the configuration and cost information, and select Launch cluster. In this example, we use cluster_neon as the cluster name. It may take a few minutes to provision your cluster. After the cluster has been provisioned, the Cluster Overview page displays.

Set up a source connector

To set up a Postgres CDC source connector for Confluent Cloud:

1. On the Cluster Overview page, under Set up connector, select Get started.

2. On the Connector Plugins page, enter Postgres into the search field.

3. Select the Postgres CDC Source connector. This is the PostgreSQL CDC Source Connector (Debezium) for Confluent Cloud. This connector will take a snapshot of the existing data and then monitor and record all subsequent row-level changes to that data.

4. On the Add Postgres CDC Source connector page:

   • Select the type of access you want to grant the connector. For the purpose of this guide, we'll select Global access, but if you are configuring a production pipeline, Confluent recommends Granular access.
   • Click the Generate API key & download button to generate an API key and secret that your connector can use to communicate with your Kafka cluster. Your applications will need this API key and secret to make requests to your Kafka cluster. Store the API key and secret somewhere safe. This is the only time you’ll see the secret.

   Click Continue.

5. On the Add Postgres CDC Source connector page:

   • Add the connection details for your Neon database. You can obtain the required details from your Neon connection string, which you can find in the Connection Details widget on the Neon Dashboard. Your connection string will look something like this:

     postgres://alex:AbC123dEf@ep-cool-darkness-123456.us-east-2.aws.neon.tech/dbname?sslmode=require

     Enter the details for your connection string into the source connector fields. Based on the sample connection string above, the values would be specified as shown below. Your values will differ.

     • Database name: dbname
     • Database server name: neon_server (This is a user-specified value that will represent the logical name of your Postgres server. Confluent uses this name as a namespace in all Kafka topic and schema names. It is also used for Avro schema namespaces if the Avro data format is used. The Kafka topic will be created with the prefix database.server.name. Only alphanumeric characters, underscores, hyphens, and dots are allowed.)
     • SSL mode: require
     • Database hostname ep-cool-darkness-123456.us-east-2.aws.neon.tech (this example shows the portion of a Neon connection string forms the database hostname)
     • Database port: 5432 (Neon uses port 5432)
     • Database username: alex
     • Database Password AbC123dEf

   • If you use Neon's IP Allow feature to limit IP addresses that can connect to Neon, you will need to add the Confluent cluster static IP addresses to your allowlist. For information about configuring allowed IPs in Neon, see Configure IP Allow. If you do not use Neon's IP Allow feature, you can skip this step.

   Click Continue.

6. Under Output Kafka record value format, select an output format for Kafka record values. The default is JSON, so we'll use that format in this guide. Other supported values include AVRO, JSON_SR, and PROTOBUF, which are schema-based message formats. If you use any of these, you must also configure a Confluent Cloud Schema Registry.

   Expand the Show advanced configurations drop-down and set the following values:

   • Under Advanced configuration
     • Ensure Slot name is set to debezium. This is the name of the replication slot you created earlier.
     • Set the Publication name to users_publication, which is the name of the publication you created earlier.
     • Set Publication auto-create mode to disabled. You've already created your publication.
   • Under Database details, set Tables included to public.users, which is the name of the Neon database table you are replicating from.

   Click Continue.

7. For Connector sizing, accept the default for the maximum number of Tasks. Tasks can be scaled up at a later time for additional throughput capacity.

   Click Continue.

8. Adjust your Connector name if desired, and review your Connector configuration, which is provided in JSON format, as shown below. We'll use the default connector name in this guide.

   {
     "connector.class": "PostgresCdcSource",
     "name": "PostgresCdcSourceConnector_0",
     "kafka.auth.mode": "KAFKA_API_KEY",
     "kafka.api.key": "2WY3UABFDN7DDFIV",
     "kafka.api.secret": "****************************************************************",
     "schema.context.name": "default",
     "database.hostname": "ep-cool-darkness-123456.us-east-2.aws.neon.tech",
     "database.port": "5432",
     "database.user": "alex",
     "database.password": "************",
     "database.dbname": "dbname",
     "database.server.name": "neon_server",
     "database.sslmode": "require",
     "publication.name": "users_publication",
     "publication.autocreate.mode": "all_tables",
     "snapshot.mode": "initial",
     "tombstones.on.delete": "true",
     "plugin.name": "pgoutput",
     "slot.name": "debezium",
     "poll.interval.ms": "1000",
     "max.batch.size": "1000",
     "event.processing.failure.handling.mode": "fail",
     "heartbeat.interval.ms": "0",
     "provide.transaction.metadata": "false",
     "decimal.handling.mode": "precise",
     "binary.handling.mode": "bytes",
     "time.precision.mode": "adaptive",
     "cleanup.policy": "delete",
     "hstore.handling.mode": "json",
     "interval.handling.mode": "numeric",
     "schema.refresh.mode": "columns_diff",
     "output.data.format": "JSON",
     "after.state.only": "true",
     "output.key.format": "JSON",
     "json.output.decimal.format": "BASE64",
     "tasks.max": "1"
   }

   Click Continue to provision the connector, which may take a few monents to complete.

Verify your Kafka stream

To verify that events are now being published to a Kafka stream in Confluent:

1. Insert a row into your users table from the Neon SQL Editor or a psql client connect to your Neon database. For example:

   -- Insert a new user
   INSERT INTO users (username, email) VALUES ('Zhang', 'zhang@example.com');

2. In Confluent Cloud, navigate to your cluster (cluster_neon in this guide) and select Topics > neon_server.public.users > Messages. Your newly inserted data should appear at the top of the list of messages.

Next steps

With events now being published to a Kafka stream, you can now set up a connection between Confluent and a supported consumer. This is quite simple using a Confluent Connector. For example, you can stream data to Databricks, Snowflake, or one of the other supported consumers. Refer to the Confluent documentation for connector-specific instructions.

References

• Quick Start for Confluent Cloud
• Publications - PostgreSQL documentation