详解MySQL 5.7 MGR单主确定主节点方法

我们行MGR年底要上线了，每天都要看官方文档学习，做测试，坚持每天写一个小知识点，有想一起学习的么~

MySQL 5.7 MGR单主确定主节点是哪个，我们可以通过成员ID来判断，然后结合read_only参数来确认。

[root@localhost ~]# mysql -uroot -p -P 3306 -h 127.0.0.1

mysql: [Warning] Using a password on the command line interface can be insecure.

Welcome to the MySQL monitor. Commands end with ; or \g.

Your MySQL connection id is 857246

Server version: 5.7.26-29-log Percona Server (GPL)

Copyright (c) 2009-2022 Percona LLC and/or its affiliates

Copyright (c) 2000, 2022, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its

affiliates. Other names may be trademarks of their respective

owners.

Type ‘help;’ or ‘\h’ for help. Type ‘\c’ to clear the current input statement.

mysql> status

————–

mysql Ver 14.14 Distrib 5.7.26-29, for Linux (x86_64) using EditLine wrAPPer

Connection id:   857246

Current database:  

Current user:    root@127.0.0.1

SSL:      Not in use

Current pager:   stdout

Using outfile:   ”

Using delimiter:  ;

Server version:   5.7.26-29-log Percona Server (GPL)

Protocol version:  10

Connection:   127.0.0.1 via TCP/IP

Server characterset:  utf8mb4

Db   characterset:  utf8mb4

Client characterset:  utf8

Conn. characterset:  utf8

TCP port:    3306

Uptime:     39 days 8 hours 53 min 39 sec

Threads: 4 Questions: 4989552 Slow queries: 731837 Opens: 930 Flush tables: 1 Open tables: 924 Queries per second avg: 1.466

————–

mysql> SHOW STATUS LIKE ‘group_replication_primary_member’;

+———————————-+————————————–+

| Variable_name          | Value                |

+———————————-+————————————–+

| group_replication_primary_member | 59d7f183-b8f6-11e9-863b-005056875165 |

+———————————-+————————————–+

1 row in set (0.00 sec)

mysql> select * from performance_schema.replication_group_members;

+—————————+————————————–+————-+————-+————–+

| CHANNEL_NAME       | MEMBER_ID              | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |

+—————————+————————————–+————-+————-+————–+

| group_replication_applier | 500dd0aa-b8f6-11e9-85ba-005056875a61 | 196.55.7.37 |    3306 | ONLINE    |

| group_replication_applier | 59d7f183-b8f6-11e9-863b-005056875165 | 196.55.7.36 |    3306 | ONLINE    |

| group_replication_applier | 69e1c26d-b8f6-11e9-91c1-00505687032a | 196.55.7.38 |    3306 | ONLINE    |

+—————————+————————————–+————-+————-+————–+

3 rows in set (0.00 sec)

mysql> show variables like ‘%read_only’;

+———————–+——-+

| Variable_name     | Value |

+———————–+——-+

| innodb_read_only   | OFF  |

| read_only       | OFF  |

| super_read_only    | OFF  |

| transaction_read_only | OFF  |

| tx_read_only     | OFF  |

+———————–+——-+

5 rows in set (0.01 sec)

mysql>

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