18.2.1.5 引导组

第一次启动组的过程称为引导。您使用 group_replication_bootstrap_group 系统变量来引导一个组。引导程序只能由一台服务器完成,即启动组的服务器,并且只能启动一次。这就是 group_replication_bootstrap_group 选项的值未存储在实例的选项文件中的原因。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同名的组。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 来停止和重新启动插件ON。因此,为了安全地引导组,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,如果您在START GROUP_REPLICATION语句(您可以从 MySQL 8.0.21 开始)上提供用于分布式恢复的用户凭据,请发出以下语句:

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;

语句返回后,该START GROUP_REPLICATION 组已启动。您可以检查该组现在是否已创建并且其中是否有一名成员:

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一个具有唯一标识符的成员 ce9be252-2b71-11e6-b8f4-00212844f856,它正在ONLINE并且正在s1 侦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: 8.0.31-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,并将它们对应的 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,因此它可以用于从捐赠者的二进制日志通过状态传输进行分布式恢复。