The administrative interface to semisynchronous replication has several components:
Two plugins implement semisynchronous capability. There is one plugin for the master side and one for the slave side.
System variables control plugin behavior. Some examples:
Controls whether semisynchronous replication is enabled on the master. To enable or disable the plugin, set this variable to 1 or 0, respectively. The default is 0 (off).
A value in milliseconds that controls how long the master waits on a commit for acknowledgment from a slave before timing out and reverting to asynchronous replication. The default value is 10000 (10 seconds).
rpl_semi_sync_master_enabled, but controls the slave plugin.
rpl_semi_sync_system variables are described at Section 5.1.4, “Server System Variables”.
Status variables enable semisynchronous replication monitoring. Some examples:
The number of semisynchronous slaves.
Whether semisynchronous replication currently is operational on the master. The value is 1 if the plugin has been enabled and a commit acknowledgment has not occurred. It is 0 if the plugin is not enabled or the master has fallen back to asynchronous replication due to commit acknowledgment timeout.
The number of commits that were not acknowledged successfully by a slave.
The number of commits that were acknowledged successfully by a slave.
Whether semisynchronous replication currently is operational on the slave. This is 1 if the plugin has been enabled and the slave I/O thread is running, 0 otherwise.
Rpl_semi_sync_status variables are described at Section 5.1.6, “Server Status Variables”.
The system and status variables are available only if the
appropriate master or slave plugin has been installed with