Processing Debezium CDC streams

Debezium is a change data capture (CDC) tool that sends database changes to other systems for processing. You can use Yandex Data Streams to capture these changes and Yandex Query to process them. You can do the following with processed data:

• Send it to Yandex Monitoring to make charts and use it in alerting.
• Write it to a stream in Data Streams and then send to Yandex Cloud Functions for processing.
• Write it to a stream in Data Streams and then transfer to Yandex Data Transfer to then distribute to various storage systems.

In this use case, you will send PostgreSQL database changes to a stream in Data Streams using Debezium and then query them with Query. The query will return the number of changes in DB tables grouped by 10s interval. It is assumed that Debezium is installed on the server with PostgreSQL set up and running.

For this tutorial:

1. Create a data stream in Data Streams.
2. Set the stream connection credentials.
3. Set up Debezium Server.
4. Connect Query to your data stream.
5. Query the data.

Getting startedGetting started

Sign up for Yandex Cloud and create a billing account:

1. Navigate to the management console and log in to Yandex Cloud or create a new account.
2. On the Yandex Cloud Billing page, make sure you have a billing account linked and it has the ACTIVE or TRIAL_ACTIVE status. If you do not have a billing account, create one and link a cloud to it.

If you have an active billing account, you can navigate to the cloud page to create or select a folder for your infrastructure.

Learn more about clouds and folders here.

Create a data stream in Data StreamsCreate a data stream in Data Streams

Create a data stream named debezium.

Set the stream connection credentialsSet the stream connection credentials

1. Create a service account and assign it the editor role for your folder.
2. Create a static access key.
3. On the server where PostgreSQL is set up and running, configure the AWS CLI:

   1. Install the AWS CLI and run this command:

      aws configure
      

   2. Enter the following, one by one:

      • AWS Access Key ID [None]:: Service account key ID.
      • AWS Secret Access Key [None]:: Service account secret key.
      • Default region name [None]:: ru-central1 availability zone.

Set up Debezium ServerSet up Debezium Server

On the server where PostgreSQL is set up and running:

1. Install the Debezium Server using this guide.

2. Go to the conf folder and create a file named application.properties with the following contents:

   debezium.sink.type=kinesis
   debezium.sink.kinesis.region=ru-central1
   debezium.sink.kinesis.endpoint=<endpoint>
   debezium.source.connector.class=io.debezium.connector.postgresql.PostgresConnector
   debezium.source.offset.storage.file.filename=data/offsets.dat
   debezium.source.offset.flush.interval.ms=0
   debezium.source.database.hostname=localhost
   debezium.source.database.port=5432
   debezium.source.database.user=<user_name>
   debezium.source.database.password=<user_password>
   debezium.source.database.dbname=<DB_name>
   debezium.source.database.server.name=debezium
   debezium.source.plugin.name=pgoutput
   
   debezium.source.transforms=Reroute
   debezium.source.transforms.Reroute.type=io.debezium.transforms.ByLogicalTableRouter
   debezium.source.transforms.Reroute.topic.regex=(.*)
   debezium.source.transforms.Reroute.topic.replacement=<data_stream>
   

   Where:

   • <endpoint>: Endpoint for a Data Streams data stream, e.g., https://yds.serverless.yandexcloud.net/ru-central1/b1g89ae43m6he********/etn01eg4rn1********. You can find the endpoint on the stream page (see Viewing a list of streams).
   • <data_stream>: Data Streams data stream name.
   • <DB_name>: PostgreSQL database name.
   • <user_name>: User name for connecting to the PostgreSQL database.
   • <user_password>: User password for connecting to the PostgreSQL database.

3. Run Debezium using this command:

   JAVA_OPTS=-Daws.cborEnabled=false ./run.sh
   

4. Make some changes to the PostgreSQL database, e.g., insert data into a table.

5. If the settings are correct, the Debezium console will show messages like:

   2022-02-11 07:31:12,850 INFO  [io.deb.con.com.BaseSourceTask] (pool-7-thread-1) 1 records sent during previous 00:19:59.999, last recorded offset: {transaction_id=null, lsn_proc=23576408, lsn_commit=23576120, lsn=23576408, txId=580, ts_usec=1644564672582666}
   

Connect Query to your data streamConnect Query to your data stream

1. Create a connection named yds-connection of the Data Streams type.
2. On the binding creation page:
   • Enter the binding name: debezium.
   • Specify the data stream: cdebezium.
   • Add a column titled data with JSON for type.
3. Click Create.

Query the dataQuery the data

Open the query editor in the Query interface and run this query:

$debezium_data = 
SELECT 
    JSON_VALUE(data,"$.payload.source.table") AS table_name, 
    DateTime::FromMilliseconds(cast(JSON_VALUE(data,"$.payload.source.ts_ms") AS Uint64)) AS `timestamp`
FROM bindings.`debezium`;

SELECT 
    table_name, 
    HOP_END() 
FROM 
    $debezium_data 
GROUP BY 
    HOP(`timestamp`, "PT10S", "PT10S", "PT10S"),
    table_name
LIMIT 2;

See alsoSee also

• Reading data from Data Streams using Query connections