PostgreSQL change data capture and delivery to YDS

You can track data changes in a Managed Service for PostgreSQL source cluster and send them to a Data Streams target cluster using change data capture (CDC).

To set up CDC using Data Transfer:

1. Set up your transfer.
2. Activate the transfer.
3. Test the replication process.

If you no longer need the resources you created, delete them.

Required paid resourcesRequired paid resources

The support cost includes:

• Managed Service for PostgreSQL cluster fee: Using computing resources allocated to hosts and disk space (see Managed Service for PostgreSQL pricing).

• Fee for using public IP addresses for cluster hosts (see Virtual Private Cloud pricing).

• Managed Service for YDB database fee. The charge depends on the usage mode:

  • For the serverless mode, you pay for data operations and the amount of stored data.
  • For the dedicated instance mode, you pay for the use of computing resources, dedicated DBs, and disk space.

  Learn more about the Managed Service for YDB pricing plans here.

• Data Streams fee, which depends on the pricing mode:

  • Provisioned capacity pricing mode: You pay for the number of write units and resources allocated for data streaming.
  • On-demand pricing mode:

    • If the DB operates in serverless mode, the data stream is charged according to the YDB serverless mode pricing policy.

    • If the DB operates in dedicated instance mode, the data stream is not charged separately (you only pay for the DB, see the pricing policy).

  Learn more about the Data Streams pricing plans here.

Getting startedGetting started

Set up your infrastructure:

Set up your transferSet up your transfer

1. Create a data stream in Data Streams named mpg-stream.

2. Connect to the Managed Service for PostgreSQL cluster, create a table named measurements in the db1 database, and populate it with data:

   CREATE TABLE measurements (
       device_id varchar(200) NOT NULL,
       datetime timestamp NOT NULL,
       latitude real NOT NULL,
       longitude real NOT NULL,
       altitude real NOT NULL,
       speed real NOT NULL,
       battery_voltage real,
       cabin_temperature real NOT NULL,
       fuel_level real,
       PRIMARY KEY (device_id)
   );
   INSERT INTO measurements VALUES
       ('iv9a94th6rzt********', '2022-06-05 17:27:00', 55.70329032, 37.65472196,  427.5,    0, 23.5, 17, NULL),
       ('rhibbh3y08qm********', '2022-06-06 09:49:54', 55.71294467, 37.66542005, 429.13, 55.5, NULL, 18, 32);
   

3. Create a target endpoint of the Data Streams type with the following settings:

   • Database: ydb-example
   • Stream: mpg-stream
   • Service account: yds-sa

4. Create a source endpoint and transfer:

   Manually

   Terraform

   1. Create a source endpoint of the PostgreSQL type and specify these cluster connection settings in it:

      • Installation type: Managed Service for PostgreSQL cluster.
      • Managed Service for PostgreSQL cluster: <PostgreSQL_source_cluster_name> from the drop-down list.
      • Database: db1.
      • User: pg-user.
      • Password: pg-user password.

   2. Create a transfer of the Replication type that will use the created endpoints.

   1. In the postgresql-yds.tf file, specify these variables:

      • yds_endpoint_id: ID of the target endpoint.
      • transfer_enabled: Set to 1 to create a transfer.

   2. Make sure the Terraform configuration files are correct using this command:

      terraform validate
      

      Terraform will show any errors found in your configuration files.

   3. Create the required infrastructure:

      1. Run this command to view the planned changes:

         terraform plan
         

         If you described the configuration correctly, the terminal will display a list of the resources to update and their parameters. This is a verification step that does not apply changes to your resources.

      2. If everything looks correct, apply the changes:

         1. Run this command:

            terraform apply
            

         2. Confirm updating the resources.

         3. Wait for the operation to complete.

Activate the transferActivate the transfer

1. Activate the transfer and wait for its status to change to Replicating.

2. Make sure the data from the source has been moved to the Data Streams stream:

   Management console

   AWS CLI

   1. In the management console, select Data Streams.
   2. Select the target stream from the list and navigate to  Data viewer.
   3. Make sure shard-000000 now contains messages with the source table rows. For a closer look at the messages, click .

   1. Install the AWS CLI.

   2. Configure the environment for Data Streams.

   3. Read the stream data using:

      • AWS CLI.
      • AWS SDK.

Test the replication processTest the replication process

1. Connect to the source cluster.

2. Add a new row to the measurements table:

   INSERT INTO measurements VALUES
       ('ad02l5ck6sdt********', '2022-06-05 17:27:00', 55.70329032, 37.65472196,  427.5,    0, 23.5, 19, 45);
   

3. Make sure you can now see the new row in your data stream.

Delete the resources you createdDelete the resources you created

Some resources are not free of charge. To avoid unnecessary charges, delete the resources you no longer need:

1. Delete the transfer.
2. Delete the target endpoint.
3. Delete the stream in Data Streams.

Delete the other resources depending on how you created them: