17.2.1.5 Bootstrapping the Group

The process of starting a group for the first time is called bootstrapping. You use the group_replication_bootstrap_group system variable to bootstrap a group. The bootstrap should only be done by a single server, the one that starts the group and only once. This is why the value of the group_replication_bootstrap_group option was not stored in the instance's option file. If it is saved in the option file, upon restart the server automatically bootstraps a second group with the same name. This would result in two distinct groups with the same name. The same reasoning applies to stopping and restarting the plugin with this option set to ON. Therefore to safely bootstrap the group, connect to s1 and issue:

mysql> SET GLOBAL group_replication_bootstrap_group=ON;
mysql> START GROUP_REPLICATION;
mysql> SET GLOBAL group_replication_bootstrap_group=OFF;

Once the START GROUP_REPLICATION statement returns, the group has been started. You can check that the group is now created and that there is one member in it:

mysql> SELECT * FROM performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+---------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE  |
+---------------------------+--------------------------------------+-------------+-------------+---------------+
| group_replication_applier | ce9be252-2b71-11e6-b8f4-00212844f856 |   s1        |       3306  | ONLINE        |
+---------------------------+--------------------------------------+-------------+-------------+---------------+

The information in this table confirms that there is a member in the group with the unique identifier ce9be252-2b71-11e6-b8f4-00212844f856, that it is ONLINE and is at s1 listening for client connections on port 3306.

For the purpose of demonstrating that the server is indeed in a group and that it is able to handle load, create a table and add some content to it.

mysql> CREATE DATABASE test;
mysql> USE test;
mysql> CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL);
mysql> INSERT INTO t1 VALUES (1, 'Luis');

Check the content of table t1 and the binary log.

mysql> SELECT * FROM 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    |         1 |         123 | Server ver: 5.7.44-log, Binlog ver: 4                              |
| binlog.000001 | 123 | Previous_gtids |         1 |         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=14724817264259180:1                                        |
| 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 |         899 | BEGIN                                                              |
| binlog.000001 | 899 | Table_map      |         1 |         942 | table_id: 108 (test.t1)                                            |
| binlog.000001 | 942 | Write_rows     |         1 |         984 | table_id: 108 flags: STMT_END_F                                    |
| binlog.000001 | 984 | Xid            |         1 |        1011 | COMMIT /* xid=38 */                                                |
+---------------+-----+----------------+-----------+-------------+--------------------------------------------------------------------+

As seen above, the database and the table objects were created and their corresponding DDL statements were written to the binary log. Also, the data was inserted into the table and written to the binary log. The importance of the binary log entries is illustrated in the following section when the group grows and distributed recovery is executed as new members try to catch up and become online.