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MySQL 8.0 Reference Manual  /  ...  /  Semisynchronous Replication Monitoring

17.4.10.3 Semisynchronous Replication Monitoring

The plugins for semisynchronous replication expose a number of status variables that enable you to monitor their operation. To check the current values of the status variables, use SHOW STATUS:

mysql> SHOW STATUS LIKE 'Rpl_semi_sync%';

From MySQL 8.0.26, new versions of the source and replica plugins are supplied, which replace the terms master and slave with source and replica in system variables and status variables. If you install the new rpl_semi_sync_source and rpl_semi_sync_replica plugins, the new system variables and status variables are available but the old ones are not. If you install the old rpl_semi_sync_master and rpl_semi_sync_slave plugins, the old system variables and status variables are available but the new ones are not. You cannot have both the new and the old version of the relevant plugin installed on an instance.

All Rpl_semi_sync_xxx status variables are described at Section 5.1.10, “Server Status Variables”. Some examples are:

When the source switches between asynchronous or semisynchronous replication due to commit-blocking timeout or a replica catching up, it sets the value of the Rpl_semi_sync_source_status or Rpl_semi_sync_master_status status variable appropriately. Automatic fallback from semisynchronous to asynchronous replication on the source means that it is possible for the rpl_semi_sync_source_enabled or rpl_semi_sync_master_enabled system variable to have a value of 1 on the source side even when semisynchronous replication is in fact not operational at the moment. You can monitor the Rpl_semi_sync_source_status or Rpl_semi_sync_master_status status variable to determine whether the source currently is using asynchronous or semisynchronous replication.