A CUBRID HA node consists of one master process (cub_master), one or more database server processes (cub_server), one or more replication log copy processes (copylogdb), and one or more replication log reflection processes (applylogdb). When a database is configured, database server processes, replication log copy processes, and replication log reflection processes will start. Because copy and reflection of a replication log are executed by different processes, the delay in replicating reflections does not affect the transaction that is being executed.
- Master process (cub_master) : Exchanges heartbeat messages to control the internal management processes of CUBRID HA.
- Database server process (cub_server) : Provides services such as read or write to the user. For more information, see Server.
- Replication log copy process (copylogdb) : Copies all transaction logs in a group. When the replication log copy process requests a transaction log from the database server process of the target node, the database server process returns the corresponding log. The location of copied transaction logs can be configured in the REPL_LOG_HOME of cubrid-ha. Use cubrid applyinfo utility to verify the information of copied replication logs. The replication log copy process has following three modes: SYNC, SEMISYNC, and ASYNC. You can configure it with the LW_SYNC_MODE of cubrid-ha. For more information on these modes, see Multiplexing Logs.
- Replication log reflection process (applylogdb) : Reflects the log that has been copied by the replication log copy process to a node. The information of reflected replications is stored in the internal catalog (db_ha_apply_info). You can use the cubrid applyinfo utility to verify this information.