Sink to TiDB Cloud

This document describes how to stream data from a TiDB Cloud Dedicated cluster to a TiDB Cloud Serverless cluster.

Restrictions

• For each TiDB Cloud cluster, you can create up to 100 changefeeds.

• Because TiDB Cloud uses TiCDC to establish changefeeds, it has the same restrictions as TiCDC.

• If the table to be replicated does not have a primary key or a non-null unique index, the absence of a unique constraint during replication could result in duplicated data being inserted downstream in some retry scenarios.

• The Sink to TiDB Cloud feature is only available to TiDB Cloud Dedicated clusters that are in the following AWS regions and created after November 9, 2022:

  • AWS Oregon (us-west-2)
  • AWS Frankfurt (eu-central-1)
  • AWS Singapore (ap-southeast-1)
  • AWS Tokyo (ap-northeast-1)

• The source TiDB Cloud Dedicated cluster and the destination TiDB Cloud Serverless cluster must be in the same project and the same region.

• The Sink to TiDB Cloud feature only supports network connection via private endpoints. When you create a changefeed to stream data from a TiDB Cloud Dedicated cluster to a TiDB Cloud Serverless cluster, TiDB Cloud will automatically set up the private endpoint connection between the two clusters.

Prerequisites

The Sink to TiDB Cloud connector can only sink incremental data from a TiDB Cloud Dedicated cluster to a TiDB Cloud Serverless cluster after a certain TSO.

Before creating a changefeed, you need to export existing data from the source TiDB Cloud Dedicated cluster and load the data to the destination TiDB Cloud Serverless cluster.

1. Extend the tidb_gc_life_time to be longer than the total time of the following two operations, so that historical data during the time is not garbage collected by TiDB.

   • The time to export and import the existing data
   • The time to create Sink to TiDB Cloud

   For example:

   SET GLOBAL tidb_gc_life_time = '720h';
   

2. Back up data from your TiDB Cloud Dedicated cluster, then use community tools such as mydumper/myloader to load data to the destination TiDB Cloud Serverless cluster.

3. From the exported files of Dumpling, get the start position of TiDB Cloud sink from the metadata file:

   The following is a part of an example metadata file. The Pos of SHOW MASTER STATUS is the TSO of the existing data, which is also the start position of TiDB Cloud sink.

   Started dump at: 2023-03-28 10:40:19
   SHOW MASTER STATUS:
           Log: tidb-binlog
           Pos: 420747102018863124
   Finished dump at: 2023-03-28 10:40:20
   

Create a TiDB Cloud sink

After completing the prerequisites, you can sink your data to the destination TiDB Cloud Serverless cluster.

1. Navigate to the cluster overview page of the target TiDB cluster, and then click Changefeed in the left navigation pane.

2. Click Create Changefeed, and select TiDB Cloud as the destination.

3. In the TiDB Cloud Connection area, select the destination TiDB Cloud Serverless cluster, and then fill in the user name and password of the destination cluster.

4. Click Next to establish the connection between the two TiDB clusters and test whether the changefeed can connect them successfully:

   • If yes, you are directed to the next step of configuration.
   • If not, a connectivity error is displayed, and you need to handle the error. After the error is resolved, click Next again.

5. Customize Table Filter to filter the tables that you want to replicate. For the rule syntax, refer to table filter rules.

   • Filter Rules: you can set filter rules in this column. By default, there is a rule *.*, which stands for replicating all tables. When you add a new rule, TiDB Cloud queries all the tables in TiDB and displays only the tables that match the rules in the box on the right. You can add up to 100 filter rules.
   • Tables with valid keys: this column displays the tables that have valid keys, including primary keys or unique indexes.
   • Tables without valid keys: this column shows tables that lack primary keys or unique keys. These tables present a challenge during replication because the absence of a unique identifier can result in inconsistent data when the downstream handles duplicate events. To ensure data consistency, it is recommended to add unique keys or primary keys to these tables before initiating the replication. Alternatively, you can add filter rules to exclude these tables. For example, you can exclude the table test.tbl1 by using the rule "!test.tbl1".

6. Customize Event Filter to filter the events that you want to replicate.

   • Tables matching: you can set which tables the event filter will be applied to in this column. The rule syntax is the same as that used for the preceding Table Filter area. You can add up to 10 event filter rules per changefeed.
   • Ignored events: you can set which types of events the event filter will exclude from the changefeed.

7. In the Start Replication Position area, fill in the TSO that you get from Dumpling exported metadata files.

8. Click Next to configure your changefeed specification.

   • In the Changefeed Specification area, specify the number of Replication Capacity Units (RCUs) to be used by the changefeed.
   • In the Changefeed Name area, specify a name for the changefeed.

9. Click Next to review the changefeed configuration.

   If you confirm that all configurations are correct, check the compliance of cross-region replication, and click Create.

   If you want to modify some configurations, click Previous to go back to the previous configuration page.

10. The sink starts soon, and you can see the status of the sink changes from Creating to Running.

    Click the changefeed name, and you can see more details about the changefeed, such as the checkpoint, replication latency, and other metrics.

11. Restore tidb_gc_life_time to its original value (the default value is 10m) after the sink is created:

    SET GLOBAL tidb_gc_life_time = '10m';