Show 17.3.9.2 Semisynchronous Replication Installation and ConfigurationSemisynchronous replication is implemented using plugins, so the plugins must be installed into the server to make them available. After a plugin has been installed, you control it by means of the system variables associated with it. These system variables are unavailable until the associated plugin has been installed. This section describes how to install the semisynchronous replication plugins. For general information about installing plugins, see Section 5.5.1, “Installing and Uninstalling Plugins”. To use semisynchronous replication, the following requirements must be satisfied:
To set up semisynchronous replication, use the following instructions. The MySQL distributions include semisynchronous replication plugin files for the source side and the replica side. To be usable by a source or replica server, the appropriate plugin library file must be located in the MySQL plugin directory (the directory named by the
The plugin library file base names are The source plugin library file must be present in the plugin directory of the source server. The replica plugin library file must be present in the plugin directory of each replica server. To load the plugins, use the On the source: INSTALL PLUGIN rpl_semi_sync_master SONAME 'semisync_master.so'; On each replica: INSTALL PLUGIN rpl_semi_sync_slave SONAME 'semisync_slave.so'; If an attempt to install a plugin results in an error on Linux similar to that shown here, you must install mysql> You can obtain To see which plugins are installed,
use the To verify plugin installation, examine the
mysql> 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 At runtime, these source-side system variables are available: SET GLOBAL rpl_semi_sync_master_enabled = {0|1};
SET GLOBAL rpl_semi_sync_master_timeout = On the replica side, this system variable is available: SET GLOBAL rpl_semi_sync_slave_enabled = {0|1}; For
For
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: STOP SLAVE IO_THREAD; START SLAVE IO_THREAD; If the I/O thread is already running and you do not restart it, the replica continues to use asynchronous replication. At server startup, the variables that control semisynchronous replication can be set as command-line options or in an option file. A setting listed in an option file takes effect each time the server starts. For example, you can set the variables in On the source: [mysqld] rpl_semi_sync_master_enabled=1 rpl_semi_sync_master_timeout=1000 # 1 second On each replica: [mysqld] rpl_semi_sync_slave_enabled=1 Is MySQL replication synchronous?MySQL replication by default is asynchronous. The source writes events to its binary log and replicas request them when they are ready. The source does not know whether or when a replica has retrieved and processed the transactions, and there is no guarantee that any event ever reaches any replica.
What is async and sync replication?Most synchronous replication products write data to primary storage and the replica simultaneously. As such, the primary copy and the replica should always remain synchronized. In contrast, asynchronous replication products write data to the primary storage first and then copy the data to the replica.
What is replication sync?Synchronous replication is the process of copying data over a storage area network, local area network or wide area network so there are multiple, current copies of the data. Synchronous replication is mainly used for high-end transactional applications that need instant failover if the primary node fails.
What is master master replication MySQL?MySQL Master Master replication is a development of master-slave replication that addresses its major flaws. This method of replication requires two or more master nodes that can handle both read and write requests. Additionally, each of your masters can have several slave nodes.
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