MySQL 5.7 Release Notes
The plugins for the semisynchronous replication capability expose several system and status variables that you can examine to determine its configuration and operational state.
The system variable reflect how semisynchronous replication is
configured. To check their values, use SHOW
VARIABLES:
mysql> SHOW VARIABLES LIKE 'rpl_semi_sync%';
The status variables enable you to monitor the operation of
semisynchronous replication. To check their values, use
SHOW STATUS:
mysql> SHOW STATUS LIKE 'Rpl_semi_sync%';
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_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_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_master_status
status variable to determine whether the source currently is
using asynchronous or semisynchronous replication.
To see how many semisynchronous replicas are connected, check
Rpl_semi_sync_master_clients.
The number of commits that have been acknowledged successfully
or unsuccessfully by replicas are indicated by the
Rpl_semi_sync_master_yes_tx
and Rpl_semi_sync_master_no_tx
variables.
On the replica side,
Rpl_semi_sync_slave_status
indicates whether semisynchronous replication currently is
operational.