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TiCDC Compatibility
Learn about compatibility issues of TiCDC and how to handle them.

TiCDC Compatibility

This section describes compatibility issues related to TiCDC and how to handle them.

CLI and configuration file compatibility

  • In TiCDC v4.0.0, ignore-txn-commit-ts is removed and ignore-txn-start-ts is added, which uses start_ts to filter transactions.
  • In TiCDC v4.0.2, db-dbs/db-tables/ignore-dbs/ignore-tables are removed and rules is added, which uses new filter rules for databases and tables. For detailed filter syntax, see Table Filter.
  • Starting from TiCDC v6.2.0, cdc cli can directly interact with TiCDC server via TiCDC Open API. You can specify the address of the TiCDC server using the --server parameter. --pd is deprecated.
  • Since v6.4.0, only the changefeed with the SYSTEM_VARIABLES_ADMIN or SUPER privilege can use the TiCDC Syncpoint feature.

Handle compatibility issues

This section describes compatibility issues related to TiCDC and how to handle them.

Incompatibility issue caused by using the TiCDC v5.0.0-rc cdc cli tool to operate a v4.0.x cluster

When using the cdc cli tool of TiCDC v5.0.0-rc to operate a v4.0.x TiCDC cluster, you might encounter the following abnormal situations:

  • If the TiCDC cluster is v4.0.8 or an earlier version, using the v5.0.0-rc cdc cli tool to create a replication task might cause cluster anomalies and get the replication task stuck.

  • If the TiCDC cluster is v4.0.9 or a later version, using the v5.0.0-rc cdc cli tool to create a replication task will cause the old value and unified sorter features to be unexpectedly enabled by default.

Solutions:

Use the cdc executable file corresponding to the TiCDC cluster version to perform the following operations:

  1. Delete the changefeed created using the v5.0.0-rc cdc cli tool. For example, run the tiup cdc:v4.0.9 cli changefeed remove -c xxxx --pd=xxxxx --force command.
  2. If the replication task is stuck, restart the TiCDC cluster. For example, run the tiup cluster restart <cluster_name> -R cdc command.
  3. Re-create the changefeed. For example, run the tiup cdc:v4.0.9 cli changefeed create --sink-uri=xxxx --pd=xxx command.

Note:

This issue exists only when cdc cli is v5.0.0-rc. cdc cli tool of other v5.0.x versions is compatible with v4.0.x clusters.

Compatibility notes for sort-dir and data-dir

The sort-dir configuration is used to specify the temporary file directory for the TiCDC sorter. Its functionalities might vary in different versions. The following table lists sort-dir's compatibility changes across versions.

Version sort-engine functionality Note Recommendation
v4.0.11 or an earlier v4.0 version, v5.0.0-rc It is a changefeed configuration item and specifies temporary file directory for the file sorter and unified sorter. In these versions, file sorter and unified sorter are experimental features and NOT recommended for the production environment.

If multiple changefeeds use the unified sorter as its sort-engine, the actual temporary file directory might be the sort-dir configuration of any changefeed, and the directory used for each TiCDC node might be different.		 It is not recommended to use unified sorter in the production environment.
v4.0.12, v4.0.13, v5.0.0, and v5.0.1 It is a configuration item of changefeed or of cdc server. By default, the sort-dir configuration of a changefeed does not take effect, and the sort-dir configuration of cdc server defaults to /tmp/cdc_sort. It is recommended to only configure cdc server in the production environment.

If you use TiUP to deploy TiCDC, it is recommended to use the latest TiUP version and set sorter.sort-dir in the TiCDC server configuration.

The unified sorter is enabled by default in v4.0.13, v5.0.0, and v5.0.1. If you want to upgrade your cluster to these versions, make sure that you have correctly configured sorter.sort-dir in the TiCDC server configuration.		 You need to configure sort-dir using the cdc server command-line parameter (or TiUP).
v4.0.14 and later v4.0 versions, v5.0.3 and later v5.0 versions, later TiDB versions sort-dir is deprecated. It is recommended to configure data-dir. You can configure data-dir using the latest version of TiUP. In these TiDB versions, unified sorter is enabled by default. Make sure that data-dir has been configured correctly when you upgrade your cluster. Otherwise, /tmp/cdc_data will be used by default as the temporary file directory.

If the storage capacity of the device where the directory is located is insufficient, the problem of insufficient hard disk space might occur. In this situation, the previous sort-dir configuration of changefeed will become invalid.		 You need to configure data-dir using the cdc server command-line parameter (or TiUP).
v6.0.0 and later versions data-dir is used for saving the temporary files generated by TiCDC. Starting from v6.0.0, TiCDC uses db sorter as the sort engine by default. data-dir is the disk directory for this engine. You need to configure data-dir using the cdc server command-line parameter (or TiUP).

Compatibility with temporary tables

Since v5.3.0, TiCDC supports global temporary tables. Replicating global temporary tables to the downstream using TiCDC of a version earlier than v5.3.0 causes table definition error.

If the upstream cluster contains a global temporary table, the downstream TiDB cluster is expected to be v5.3.0 or a later version. Otherwise, an error occurs during the replication process.