16.3.8.1. Semisynchronous Replication Administrative Interface

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:
- rpl_semi_sync_master_enabled
  
  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).
- rpl_semi_sync_master_timeout
  
  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_slave_enabled
  
  Similar to rpl_semi_sync_master_enabled, but controls the slave plugin.
All rpl_semi_sync_xxx system variables are described at Section 5.1.4, "Server System Variables".
Status variables enable semisynchronous replication monitoring. Some examples:
- Rpl_semi_sync_master_clients
  
  The number of semisynchronous slaves.
- Rpl_semi_sync_master_status
  
  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.
- Rpl_semi_sync_master_no_tx
  
  The number of commits that were not acknowledged successfully by a slave.
- Rpl_semi_sync_master_yes_tx
  
  The number of commits that were acknowledged successfully by a slave.
- Rpl_semi_sync_slave_status
  
  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.
All Rpl_semi_sync_xxx 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 INSTALL PLUGIN.