In previous releases, the periodic updates to the last_check_in field of the mysql_innodb_cluster_metadata.routers table generated very large binary logs. This was caused by MySQL Router storing full configuration details in the attributes field of the mysql_innodb_cluster_metadata.routers table and the entire row being copied to the binary log every time last_check_in was updated.

As of this release, a new version of the Metadata Schema is added, v2.4.0. In this version, last_check_in is moved to a new table, mysql_innodb_cluster_metadata.router_stats.

If the schema version is less than 2.4.0, MySQL Router carries on using mysql_innodb_cluster_metadata.routers.last_check_in. If the schema version is 2.4.0, or higher, MySQL Router uses mysql_innodb_cluster_metadata.router_stats.last_check_in. (Bug #37926324, WL #17027, WL #17028)