This is the second post in a two-part blog series discussing how to stream database changes into Kafka. You can read part one here. We will discuss adding a Kafka target to the CDC source from the previous post. The application will ingest database changes (inserts, updates, and deletes) from the PostgreSQL source tables and deliver to Kafka to continuously to update a Kafka topic.
What is Kafka?
Apache Kafka is a popular distributed, fault-tolerant, high-performance messaging system.
Why use Striim with Kafka?
The Striim platform enables you to ingest data into Kafka, process it for different consumers, analyze, visualize, and distribute to a broad range of systems on-premises and in the cloud with an intuitive UI and SQL-based language for easy and fast development.
How to add a Kafka Target to a Striim Dataflow
From the Striim Apps page, click on the app that we created in the previous blog post and select Manage Flow.
This will open your application in the Flow Designer.
To do the writing to Kafka, we need to add a Target component into the dataflow. Click on the data stream, then on the plus (+) button, and select “Connect next Target component” from the menu.
Enter the Target Info
The next step is to specify how to write data to the target. With the New Target ADAPTER drop-down, select Kafka Writer Version 0.11.0, and enter a few connection properties including the target name, topic and broker URL.
Different Kafka consumers may have different requirements for the data format. When writing to Kafka in Striim, you can choose the data format with the FORMATTER drop down and optional configuration properties. Striim supports JSON, Delimited, XML, Avro and free text formats, in this case we are selecting the JSONFormatter.
Deploying and Starting the Data Flow
The resulting data flow can now be modified, deployed, and started through the UI. In order to run the application, it first needs to be deployed, click on the ‘Created’ dropdown and select ‘Deploy App’ to show the Deploy UI.
The application can be deployed to all nodes, any one node, or predefined groups in a Striim cluster, the default is the least used node.
After deployment the application is ready to start, by selecting Start App.
Testing the Data Flow
You can use the PostgreSQL to Kafka sample integration application, to insert, delete, and update the PosgtreSQL CDC source table, then you should see data flowing in the UI, indicated by a number of msgs/s. (Note the message sending happens fast and quickly returns to 0).
If you now click on the data stream in the middle and click on the eye icon, you can preview the data flowing between PostgreSQL and Kafka. Here you can see the data, metadata (these are all updates) and before values (what the data was before the update).