# 18.2.1.5 引导组

首次启动组的过程称为引导。您使用group_replication_bootstrap_group引导组的系统变量。引导只能由单个服务器完成,即启动组的服务器并且只执行一次。这就是为什么价值group_replication_bootstrap_group选项未存储在实例的选项文件中。如果它保存在选项文件中,则在重新启动服务器时会自动引导第二个具有相同名称的组。这将导致两个不同的组具有相同的名称。相同的推理适用于将此选项设置为的停止和重新启动插件.因此,要安全地引导组,请连接到 s1 并发出以下语句:

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

或者,如果您要为分布式恢复提供用户凭据开始 GROUP_REPLICATION语句(您可以从 MySQL 8.0.21 开始),发出以下语句:

mysql> SET GLOBAL group_replication_bootstrap_group=ON;
mysql> START GROUP_REPLICATION USER='rpl_user', PASSWORD='password';
mysql> SET GLOBAL group_replication_bootstrap_group=OFF;

一旦开始 GROUP_REPLICATION语句返回,组已启动。您可以检查该组现在是否已创建并且其中有一个成员:

mysql> SELECT * FROM performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+---------------+-------------+----------------+----------------------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE  | MEMBER_ROLE | MEMBER_VERSION | MEMBER_COMMUNICATION_STACK |
+---------------------------+--------------------------------------+-------------+-------------+---------------+-------------+----------------+----------------------------+
| group_replication_applier | ce9be252-2b71-11e6-b8f4-00212844f856 |   s1        |       3306  | ONLINE        |             |                | XCom                       |
+---------------------------+--------------------------------------+-------------+-------------+---------------+-------------+----------------+----------------------------+
1 row in set (0.0108 sec)

此表中的信息确认组中有具有唯一标识符的成员ce9be252-2b71-11e6-b8f4-00212844f856, 这是在线的并且在s1监听端口上的客户端连接3306.

为了证明服务器确实在一个组中并且它能够处理负载,创建一个表并向其中添加一些内容。

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');

检查表的内容t1和二进制日志。

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: 8.0.28-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 */                                                |
+---------------+-----+----------------+-----------+-------------+--------------------------------------------------------------------+

如上所示,创建了数据库和表对象,并将其相应的 DDL 语句写入二进制日志。此外,数据被插入到表中并写入二进制日志,因此可以通过来自捐赠者的二进制日志的状态转移来进行分布式恢复。