Semisynchronous Replication On the source: On each replica: If an attempt to install a plugin results in an error on Linux similar to that shown here, you must install libimf : You can obtain  libimf  from https://dev.mysql.com/downloads/os-linux.html. To see which plugins are installed, use the  SHOW PLUGINS  statement, or query the INFORMATION_SCHEMA.PLUGINS  table. To verify plugin installation, examine the  INFORMATION_SCHEMA.PLUGINS  table or use the  SHOW PLUGINS  statement (see Section 5.6.2, “Obtaining Server Plugin Information” ). For example: If the plugin fails to initialize, check the server error log for diagnostic messages. After a semisynchronous replication plugin has been installed, it is disabled by default. The plugins must be enabled both on the source side and the replica side to enable semisynchronous replication. If only one side is enabled, replication is asynchronous. To control whether an installed plugin is enabled, set the appropriate system variables. You can set these variables at runtime using  SET GLOBAL , or at server startup on the command line or in an option file. At runtime, these source-side system variables are available: For  rpl_semi_sync_master_enabled  or  rpl_semi_sync_slave_enabled , the value should be 1 to enable semisynchronous replication or 0 to disable it. By default, these variables are set to 0. For  rpl_semi_sync_master_timeout , the value  N  is given in milliseconds. The default value is 10000 (10 seconds). If you enable semisynchronous replication on a replica at runtime, you must also start the replication I/O thread (stopping it first if it is already running) to cause the replica to connect to the source and register as a semisynchronous replica: On the replica side, this system variable is available: SET GLOBAL rpl_semi_sync_slave_enabled = {0|1}; SET GLOBAL rpl_semi_sync_master_enabled = {0|1}; SET GLOBAL rpl_semi_sync_master_timeout =  N ; mysql>  SELECT PLUGIN_NAME, PLUGIN_STATUS FROM INFORMATION_SCHEMA.PLUGINS WHERE PLUGIN_NAME LIKE ’%semi%’; +----------------------+---------------+ | PLUGIN_NAME | PLUGIN_STATUS | +----------------------+---------------+ | rpl_semi_sync_master | ACTIVE | +----------------------+---------------+ mysql>  INSTALL PLUGIN rpl_semi_sync_master SONAME ’semisync_master.so’; ERROR 1126 (HY000): Can’t open shared library ’/usr/local/mysql/lib/plugin/semisync_master.so’ (errno: 22 libimf.so: cannot open shared object file: No such file or directory) INSTALL PLUGIN rpl_semi_sync_slave SONAME ’semisync_slave.so’; INSTALL PLUGIN rpl_semi_sync_master SONAME ’semisync_master.so’; 3650