This section describes replication between MySQL servers based on the binary log file position method, where the MySQL instance operating as the source (where the database changes take place) writes updates and changes as “events” to the binary log. The information in the binary log is stored in different logging formats according to the database changes being recorded. Replicas are configured to read the binary log from the source and to execute the events in the binary log on the replica's local database.
Each replica receives a copy of the entire contents of the binary log. It is the responsibility of the replica to decide which statements in the binary log should be executed. Unless you specify otherwise, all events in the source's binary log are executed on the replica. If required, you can configure the replica to process only events that apply to particular databases or tables.
You cannot configure the source to log only certain events.
Each replica keeps a record of the binary log coordinates: the file name and position within the file that it has read and processed from the source. This means that multiple replicas can be connected to the source and executing different parts of the same binary log. Because the replicas control this process, individual replicas can be connected and disconnected from the server without affecting the source's operation. Also, because each replica records the current position within the binary log, it is possible for replicas to be disconnected, reconnect and then resume processing.
The source and each replica must be configured with a unique ID
variable). In addition, each replica must be configured with
information about the source's host name, log file name, and
position within that file. These details can be controlled from
within a MySQL session using a
REPLICATION SOURCE TO statement (from MySQL 8.0.23) or
CHANGE MASTER TO statement (before
MySQL 8.0.23) on the replica. The details are stored within the
replica's connection metadata repository (see
Section 17.2.4, “Relay Log and Replication Metadata Repositories”).