Adding additional instances to the group is essentially the same sequence of steps as adding the second server, except that the configuration has to be changed as it had to be for server s2. To summarise the required commands:
Create the configuration file.
[mysqld] # # Disable other storage engines # disabled_storage_engines="MyISAM,BLACKHOLE,FEDERATED,ARCHIVE,MEMORY" # # Replication configuration parameters # server_id=3 gtid_mode=ON enforce_gtid_consistency=ON binlog_checksum=NONE # Not needed from 8.0.21 # # Group Replication configuration # plugin_load_add='group_replication.so' group_replication_group_name="aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa" group_replication_start_on_boot=off group_replication_local_address= "s3:33061" group_replication_group_seeds= "s1:33061,s2:33061,s3:33061" group_replication_bootstrap_group= off
Start the server and connect to it. Create the replication user for distributed recovery.
SET SQL_LOG_BIN=0;CREATE USERrpl_user@'%' IDENTIFIED BY 'password';GRANT REPLICATION SLAVE ON *.* TOrpl_user@'%';GRANT BACKUP_ADMIN ON *.* TOrpl_user@'%';FLUSH PRIVILEGES;SET SQL_LOG_BIN=1;
If you are providing user credentials using a CHANGE REPLICATION SOURCE TO | CHANGE MASTER TO statement, issue the following statement after that:
CHANGE MASTER TO MASTER_USER='Or from MySQL 8.0.23:rpl_user', MASTER_PASSWORD='password' \\ FOR CHANNEL 'group_replication_recovery';CHANGE REPLICATION SOURCE TO SOURCE_USER='rpl_user', SOURCE_PASSWORD='password' \\ FOR CHANNEL 'group_replication_recovery';
Install the Group Replication plugin if necessary.
INSTALL PLUGIN group_replication SONAME 'group_replication.so';
Start Group Replication.
mysql> START GROUP_REPLICATION;
Or if you are providing user credentials for distributed recovery on the START GROUP_REPLICATION statement (which you can from MySQL 8.0.21):
mysql> START GROUP_REPLICATION USER='rpl_user', PASSWORD='password';At this point server s3 is booted and running, has joined the group and caught up with the other servers in the group. Consulting the performance_schema.replication_group_members table again confirms this is the case.
mysql> SELECT * FROM performance_schema.replication_group_members; +---------------------------+--------------------------------------+-------------+-------------+---------------+ | CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | +---------------------------+--------------------------------------+-------------+-------------+---------------+ | group_replication_applier | 395409e1-6dfa-11e6-970b-00212844f856 | s1 | 3306 | ONLINE | | group_replication_applier | 7eb217ff-6df3-11e6-966c-00212844f856 | s3 | 3306 | ONLINE | | group_replication_applier | ac39f1e6-6dfa-11e6-a69d-00212844f856 | s2 | 3306 | ONLINE | +---------------------------+--------------------------------------+-------------+-------------+---------------+
Issuing this same query on server s2 or server s1 yields the same result. Also, you can verify that server s3 has caught up:
mysql>SHOW DATABASES LIKE 'test';+-----------------+ | Database (test) | +-----------------+ | test | +-----------------+ mysql>SELECT * FROM test.t1;+----+------+ | c1 | c2 | +----+------+ | 1 | Luis | +----+------+ mysql>SHOW BINLOG EVENTS;+---------------+------+----------------+-----------+-------------+--------------------------------------------------------------------+ | Log_name | Pos | Event_type | Server_id | End_log_pos | Info | +---------------+------+----------------+-----------+-------------+--------------------------------------------------------------------+ | binlog.000001 | 4 | Format_desc | 3 | 123 | Server ver: 8.0.25-log, Binlog ver: 4 | | binlog.000001 | 123 | Previous_gtids | 3 | 150 | | | binlog.000001 | 150 | Gtid | 1 | 211 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1' | | binlog.000001 | 211 | Query | 1 | 270 | BEGIN | | binlog.000001 | 270 | View_change | 1 | 369 | view_id=14724832985483517:1 | | binlog.000001 | 369 | Query | 1 | 434 | COMMIT | | binlog.000001 | 434 | Gtid | 1 | 495 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:2' | | binlog.000001 | 495 | Query | 1 | 585 | CREATE DATABASE test | | binlog.000001 | 585 | Gtid | 1 | 646 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:3' | | binlog.000001 | 646 | Query | 1 | 770 | use `test`; CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL) | | binlog.000001 | 770 | Gtid | 1 | 831 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:4' | | binlog.000001 | 831 | Query | 1 | 890 | BEGIN | | binlog.000001 | 890 | Table_map | 1 | 933 | table_id: 108 (test.t1) | | binlog.000001 | 933 | Write_rows | 1 | 975 | table_id: 108 flags: STMT_END_F | | binlog.000001 | 975 | Xid | 1 | 1002 | COMMIT /* xid=29 */ | | binlog.000001 | 1002 | Gtid | 1 | 1063 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:5' | | binlog.000001 | 1063 | Query | 1 | 1122 | BEGIN | | binlog.000001 | 1122 | View_change | 1 | 1261 | view_id=14724832985483517:2 | | binlog.000001 | 1261 | Query | 1 | 1326 | COMMIT | | binlog.000001 | 1326 | Gtid | 1 | 1387 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:6' | | binlog.000001 | 1387 | Query | 1 | 1446 | BEGIN | | binlog.000001 | 1446 | View_change | 1 | 1585 | view_id=14724832985483517:3 | | binlog.000001 | 1585 | Query | 1 | 1650 | COMMIT | +---------------+------+----------------+-----------+-------------+--------------------------------------------------------------------+