17.2.1.5 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:

mysql> SET GLOBAL group_replication_bootstrap_group=ON;
mysql> START GROUP_REPLICATION;
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  |
+---------------------------+--------------------------------------+-------------+-------------+---------------+
| group_replication_applier | ce9be252-2b71-11e6-b8f4-00212844f856 |   s1        |       3306  | ONLINE        |
+---------------------------+--------------------------------------+-------------+-------------+---------------+

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: 5.7.40-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。二进制日志条目的重要性在下一节中说明,当组增长并且随着新成员试图赶上并上线而执行分布式恢复时。