19.1.7.2 Pausing Replication on the Replica

You can stop and start replication on the replica using the STOP REPLICA and START REPLICA statements.

To stop processing of the binary log from the source, use STOP REPLICA:

mysql> STOP REPLICA;

When replication is stopped, the replication I/O (receiver) thread stops reading events from the source binary log and writing them to the relay log, and the SQL thread stops reading events from the relay log and executing them. You can pause the I/O (receiver) or SQL (applier) thread individually by specifying the thread type:

mysql> STOP REPLICA IO_THREAD;
mysql> STOP REPLICA SQL_THREAD;

To start execution again, use the START REPLICA statement:

mysql> START REPLICA;

To start a particular thread, specify the thread type:

mysql> START REPLICA IO_THREAD;
mysql> START REPLICA SQL_THREAD;

For a replica that performs updates only by processing events from the source, stopping only the SQL thread can be useful if you want to perform a backup or other task. The I/O (receiver) thread continues to read events from the source but they are not executed. This makes it easier for the replica to catch up when you restart the SQL (applier) thread.

Stopping only the receiver thread enables the events in the relay log to be executed by the applier thread up to the point where the relay log ends. This can be useful when you want to pause execution to catch up with events already received from the source, when you want to perform administration on the replica but also ensure that it has processed all updates to a specific point. This method can also be used to pause event receipt on the replica while you conduct administration on the source. Stopping the receiver thread but permitting the applier thread to run helps ensure that there is not a massive backlog of events to be executed when replication is started again.