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-tsis removed andignore-txn-start-tsis added, which uses start_ts to filter transactions. - In TiCDC v4.0.2,
db-dbs/db-tables/ignore-dbs/ignore-tablesare removed andrulesis added, which uses new filter rules for databases and tables. For detailed filter syntax, see Table Filter. - Starting from TiCDC v6.2.0,
cdc clican directly interact with TiCDC server via TiCDC Open API. You can specify the address of the TiCDC server using the--serverparameter.--pdis deprecated. - Since v6.4.0, only the changefeed with the
SYSTEM_VARIABLES_ADMINorSUPERprivilege 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 clitool 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 clitool 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:
- Delete the changefeed created using the v5.0.0-rc
cdc clitool. For example, run thetiup cdc:v4.0.9 cli changefeed remove -c xxxx --pd=xxxxx --forcecommand. - If the replication task is stuck, restart the TiCDC cluster. For example, run the
tiup cluster restart <cluster_name> -R cdccommand. - Re-create the changefeed. For example, run the
tiup cdc:v4.0.9 cli changefeed create --sink-uri=xxxx --pd=xxxcommand.
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.