MGR集群搭建

2019/06/23 13:33
阅读数 95

  MGR全称MySQL Group Replication(Mysql组复制),是MySQL官方于2016年12月推出的一个全新的高可用与高扩展的解决方案。MGR提供了高可用、高扩展、高可靠的MySQL集群服务。在MGR出现之前,用户常见的MySQL高可用方式,无论怎么变化架构,本质就是Master-Slave架构。MySQL 5.7版本开始支持无损半同步复制(lossless semi-sync replication),从而进一步提示数据复制的强一致性。

  MGR是MySQL数据库未来发展的一个重要方向。

  注意:根据本人测试group_replication.so插件是mysql-community-server安装包中携带,如果是rpm安装或yum安装存放地址为/usr/lib64/mysql/plugin/目录下,看下图。另外在安装5.7.16版本时是没有这个插件,而在安装5.7.20版本有这个插件,推测这是一个5.7.16到5.7.20之间新加的插件,个人建议安装5.7.20以上的版本。另外大家请在安装好mysql后查看一下是否存在这个插件。

  如果提示group_replication.so不存在,或提示有问题并且查看时发现group_replication.so不存在,请重点看一下mysql的版本。(我搜了一大圈,没有一个人说这个问题。表示怀疑自己,如果我错了,请留言。)

(1).MGR的特性

  高一致性。基于原生复制及paxos协议的组复制技术,并以插件的方式提供,提供一致数据安全保证;

  高容错性。只要不是大多数节点坏掉就可以继续工作,有自动检测机制,当不同节点产生资源争用冲突时,不会出现错误,按照先到者优先原则进行处理,并且内置了自动化脑裂防护机制;

  高扩展性。节点的新增和移除都是自动的,新节点加入后,会自动从其他节点上同步状态,直到新节点和其他节点保持一致,如果某节点被移除了,其他节点自动更新组信息,自动维护新的组信息;

  高灵活性。有单主模式和多主模式,单主模式下,会自动选主,所有更新操作都在主上进行;多主模式下,所有server都可以同时处理更新操作。

(2).搭建MGR的基础结构要求和使用限制(重点)

  基础结构要求:1.引擎必须为innodb,因为需事务支持在commit时对各节点进行冲突检查;2.每个表必须有主键,在进行事务冲突检测时需要利用主键值对比;3.必须开启binlog且为row格式;4.开启GTID,且主从状态信息存于表中(--master-info-repository=TABLE 、--relay-log-info-repository=TABLE),--log-slave-updates打开;5.一致性检测设置--transaction-write-set-extraction=XXHASH64。

  使用限制:1.RP和普通复制binlog校验不能共存,需设置--binlog-checksum=none;2.不支持gap lock(间隙锁),隔离级别需设置为read_committed;3.不支持对表进行锁操作(lock /unlock table),不会发送到其他节点执行 ,影响需要对表进行加锁操作的情况,列入mysqldump全表备份恢复操作;4.不支持serializable(序列化)隔离级别;5.DDL语句不支持原子性,不能检测冲突,执行后需自行校验是否一;6.多主模式下不支持外键,单主模式下支持外键;最多9个节点,超过9台无法加入集群

(3).实验环境

youxi1  192.168.1.6  CentOS7.6  Mysql5.7.26  端口号3306  server-id=1

youxi2  192.168.1.7  CentOS7.6  Mysql5.7.26  端口号3306  server-id=2

youxi3  192.168.1.8  CentOS7.6  Mysql5.7.26  端口号3306  server-id=3

  另外,三台服务器上都进行IP的映射(如果此处不映射,请修改/etc/my.cnf配置文件中对应的域名为IP地址)

[root@youxi1 ~]# vim /etc/hosts
192.168.1.6 youxi1.cn youxi1  //长域名和短域名只要映射一个即可
192.168.1.7 youxi2.cn youxi2
192.168.1.8 youxi3.cn youxi3

(1).单主模式

  我是在空数据库下操作,如果主数据集已存在数据,需要将主数据库的数据导出再导入到从数据库。另外还需保证引擎为innodb,每个表必须存在主键。

1)以youxi1作为主服务器,对youxi1进行配置

  创建一个复制用的用户

mysql> grant replication slave on *.* to 'repl'@'192.168.1.%' identified by '12345678';
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)

  修改配置文件,加入到[mysqld]模块下。然后重启mysqld

[root@youxi1 ~]# vim /etc/my.cnf
server-id=1  //Mysql服务ID
gtid-mode=on  //全局事务
enforce-gtid-consistency=on  //强制GTID的一致性
master-info-repository=TABLE  //将master.info元数据保存在系统表中
relay-log-info-repository=TABLE  //将relay.info元数据保存在系统表中
binlog-checksum=none  //禁用二进制日志事件校验
log-slave-updates=on  //级联复制
log-bin=binlog  //开启二进制日志记录
binlog-format=ROW  //以行的格式记录

transaction-write-set-extraction=XXHASH64  //使用哈希算法将其编码为散列
loose-group_replication_group_name='ce9be252-2b71-11e6-b8f4-00212844f856'  //加入的组名,可以修改,只要格式对
loose-group_replication_start_on_boot=off  //不自动启用组复制集群
loose-group_replication_local_address='youxi1:33061'  //以本机端口33061接受来自组中成员的传入连接
loose-group_replication_group_seeds='youxi1:33061,youxi2:33062,youxi3:33063'  //组中成员访问表
loose-group_replication_bootstrap_group=off  //不启用引导组
[root@youxi1 ~]# systemctl restart mysqld

  注意:如果防火墙是打开的,记得添加mysql的端口号。

[root@youxi1 ~]# firewall-cmd --permanent --zone=public --add-port={3306,33061}/tcp
success
[root@youxi1 ~]# firewall-cmd --reload
success
[root@youxi1 ~]# firewall-cmd --zone=public --list-ports
3306/tcp 33061/tcp

  修改master信息,构建组复制(group replication)集群信息

mysql> change master to master_user='repl',master_password='12345678' for channel 'group_replication_recovery';
Query OK, 0 rows affected, 2 warnings (0.04 sec)

  安装组复制(group replication)插件,并查看组件信息

mysql> install PLUGIN group_replication SONAME 'group_replication.so';
Query OK, 0 rows affected (0.21 sec)

mysql> show plugins;  //查看组件是否安装成功
+----------------------------+----------+--------------------+----------------------+---------+
| Name                       | Status   | Type               | Library              | License |
+----------------------------+----------+--------------------+----------------------+---------+
| binlog                     | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| mysql_native_password      | ACTIVE   | AUTHENTICATION     | NULL                 | GPL     |
| sha256_password            | ACTIVE   | AUTHENTICATION     | NULL                 | GPL     |
| CSV                        | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| MEMORY                     | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| InnoDB                     | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| INNODB_TRX                 | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_LOCKS               | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_LOCK_WAITS          | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMP                 | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMP_RESET           | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMPMEM              | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMPMEM_RESET        | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMP_PER_INDEX       | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_CMP_PER_INDEX_RESET | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_BUFFER_PAGE         | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_BUFFER_PAGE_LRU     | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_BUFFER_POOL_STATS   | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_TEMP_TABLE_INFO     | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_METRICS             | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_DEFAULT_STOPWORD | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_DELETED          | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_BEING_DELETED    | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_CONFIG           | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_INDEX_CACHE      | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_FT_INDEX_TABLE      | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_TABLES          | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_TABLESTATS      | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_INDEXES         | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_COLUMNS         | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_FIELDS          | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_FOREIGN         | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_FOREIGN_COLS    | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_TABLESPACES     | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_DATAFILES       | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| INNODB_SYS_VIRTUAL         | ACTIVE   | INFORMATION SCHEMA | NULL                 | GPL     |
| MyISAM                     | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| MRG_MYISAM                 | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| PERFORMANCE_SCHEMA         | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| ARCHIVE                    | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| BLACKHOLE                  | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| FEDERATED                  | DISABLED | STORAGE ENGINE     | NULL                 | GPL     |
| partition                  | ACTIVE   | STORAGE ENGINE     | NULL                 | GPL     |
| ngram                      | ACTIVE   | FTPARSER           | NULL                 | GPL     |
| validate_password          | DISABLED | VALIDATE PASSWORD  | validate_password.so | GPL     |
| group_replication          | ACTIVE   | GROUP REPLICATION  | group_replication.so | GPL     |
+----------------------------+----------+--------------------+----------------------+---------+
46 rows in set (0.00 sec)

  作为主服务器需要由这台服务器开启引导,开启组复制(group replication)集群

mysql> set global group_replication_bootstrap_group=on;  //开启组复制引导
Query OK, 0 rows affected (0.00 sec)

mysql> start group_replication;  //开启组复制
Query OK, 0 rows affected (2.24 sec)

mysql> set global group_replication_bootstrap_group=off;  //关闭组复制引导
Query OK, 0 rows affected (0.00 sec)

  查看到添加到组复制集群的服务器信息

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | c9e3662b-9020-11e9-94aa-000c29721e89 | youxi1      |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
1 row in set (0.00 sec)

2)对youxi2进行配置

  创建一个复制用的用户

mysql> grant replication slave on *.* to 'repl'@'192.168.1.%' identified by '12345678';
Query OK, 0 rows affected, 1 warning (0.01 sec)

mysql> flush privileges; 
Query OK, 0 rows affected (0.01 sec)

  修改配置文件,加入到[mysqld]模块下。然后重启mysqld

[root@youxi2 ~]# vim /etc/my.cnf
server-id=2  //修改
gtid-mode=on
enforce-gtid-consistency=on
master-info-repository=TABLE
relay-log-info-repository=TABLE
binlog-checksum=none
log-slave-updates=on
log-bin=binlog
binlog-format=ROW

transaction-write-set-extraction=XXHASH64
loose-group_replication_group_name='ce9be252-2b71-11e6-b8f4-00212844f856'
loose-group_replication_start_on_boot=off
loose-group_replication_local_address='youxi2:33062'  //修改
loose-group_replication_group_seeds='youxi1:33061,youxi2:33062,youxi3:33063'
loose-group_replication_bootstrap_group=off
[root@youxi2 ~]# systemctl restart mysqld

  注意:如果防火墙是打开的,记得添加mysql的端口号。

[root@youxi2 ~]# firewall-cmd --permanent --zone=public --add-port={3306,33062}/tcp
success
[root@youxi2 ~]# firewall-cmd --reload
success
[root@youxi2 ~]# firewall-cmd --zone=public --list-ports
3306/tcp 33062/tcp

  修改master信息,构建组复制(group replication)集群信息

mysql> change master to master_user='repl',master_password='12345678' for channel 'group_replication_recovery';
Query OK, 0 rows affected, 2 warnings (0.05 sec)

  安装组复制(group replication)插件

mysql> install PLUGIN group_replication SONAME 'group_replication.so';
Query OK, 0 rows affected (0.35 sec)

  把youxi2加到之前的组复制(group replication)

mysql> set global group_replication_allow_local_disjoint_gtids_join=ON;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> start group_replication;
Query OK, 0 rows affected, 1 warning (5.92 sec)

  查看到添加到组复制集群的服务器信息

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 8fbf8b41-84fe-11e9-897e-000c29f27e52 | youxi2      |        3306 | ONLINE       |
| group_replication_applier | c9e3662b-9020-11e9-94aa-000c29721e89 | youxi1      |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
2 rows in set (0.00 sec)

3)youxi3的配置与youxi2的配置几乎一样,只需在/etc/my.cnf修改server-id和loose-group_replication_local_address即可。

  查看一下组复制集群信息

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 74df3399-91b8-11e9-be5f-000c299fdf40 | youxi3      |        3306 | ONLINE       |
| group_replication_applier | 8fbf8b41-84fe-11e9-897e-000c29f27e52 | youxi2      |        3306 | ONLINE       |
| group_replication_applier | c9e3662b-9020-11e9-94aa-000c29721e89 | youxi1      |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.01 sec)

  注意:如果防火墙是打开的,记得添加mysql的端口号。

[root@youxi3 ~]# firewall-cmd --permanent --zone=public --add-port=3306/tcp
success
[root@youxi3 ~]# firewall-cmd --permanent --zone=public --add-port=33063/tcp
success
[root@youxi3 ~]# firewall-cmd --reload
success
[root@youxi3 ~]# firewall-cmd --zone=public --list-ports
3306/tcp 33063/tcp

4)测试

  在youxi1上创建数据

mysql> create database test_db;
Query OK, 1 row affected (0.00 sec)

mysql> use test_db;
Database changed
mysql> create table user_tb(id int key,name varchar(20));  //id是主键,引擎默认是innodb
Query OK, 0 rows affected (0.02 sec)

mysql> insert into user_tb values(1,'zhangsan');
Query OK, 1 row affected (0.08 sec)

  在youxi2上查看

mysql> select * from test_db.user_tb;
+----+----------+
| id | name     |
+----+----------+
|  1 | zhangsan |
+----+----------+
1 row in set (0.00 sec)

  在youxi3上查看

mysql> select * from test_db.user_tb;
+----+----------+
| id | name     |
+----+----------+
|  1 | zhangsan |
+----+----------+
1 row in set (0.00 sec)

5)那么怎么区分主从服务器

  MGR区分主从服务器使用show variables like '%read_only%';查看read_only相关参数。如果是主服务器(youxi1),会显示如下:

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 (0.00 sec)

  如果是从服务器(youxi2)会显示如下:

mysql> show variables like '%read_only%';
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | ON    |
| super_read_only       | ON    |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.01 sec)

6)查看当前服务器的组复制集群参数设置列表

mysql> show variables like 'group_replication%';
+----------------------------------------------------+----------------------------------------+
| Variable_name                                      | Value                                  |
+----------------------------------------------------+----------------------------------------+
| group_replication_allow_local_disjoint_gtids_join  | OFF                                    |
| group_replication_allow_local_lower_version_join   | OFF                                    |
| group_replication_auto_increment_increment         | 7                                      |
| group_replication_bootstrap_group                  | OFF                                    |
| group_replication_components_stop_timeout          | 31536000                               |
| group_replication_compression_threshold            | 1000000                                |
| group_replication_enforce_update_everywhere_checks | OFF                                    |
| group_replication_exit_state_action                | READ_ONLY                              |
| group_replication_flow_control_applier_threshold   | 25000                                  |
| group_replication_flow_control_certifier_threshold | 25000                                  |
| group_replication_flow_control_mode                | QUOTA                                  |
| group_replication_force_members                    |                                        |
| group_replication_group_name                       | ce9be252-2b71-11e6-b8f4-00212844f856   |
| group_replication_group_seeds                      | youxi1:33061,youxi2:33062,youxi3:33063 |
| group_replication_gtid_assignment_block_size       | 1000000                                |
| group_replication_ip_whitelist                     | AUTOMATIC                              |
| group_replication_local_address                    | youxi1:33061                           |
| group_replication_member_weight                    | 50                                     |
| group_replication_poll_spin_loops                  | 0                                      |
| group_replication_recovery_complete_at             | TRANSACTIONS_APPLIED                   |
| group_replication_recovery_reconnect_interval      | 60                                     |
| group_replication_recovery_retry_count             | 10                                     |
| group_replication_recovery_ssl_ca                  |                                        |
| group_replication_recovery_ssl_capath              |                                        |
| group_replication_recovery_ssl_cert                |                                        |
| group_replication_recovery_ssl_cipher              |                                        |
| group_replication_recovery_ssl_crl                 |                                        |
| group_replication_recovery_ssl_crlpath             |                                        |
| group_replication_recovery_ssl_key                 |                                        |
| group_replication_recovery_ssl_verify_server_cert  | OFF                                    |
| group_replication_recovery_use_ssl                 | OFF                                    |
| group_replication_single_primary_mode              | ON                                     |
| group_replication_ssl_mode                         | DISABLED                               |
| group_replication_start_on_boot                    | OFF                                    |
| group_replication_transaction_size_limit           | 0                                      |
| group_replication_unreachable_majority_timeout     | 0                                      |
+----------------------------------------------------+----------------------------------------+
36 rows in set (0.00 sec)

7)如果主服务器出问题,MGR会自动切换主服务器

  将youxi1的mysqld人为关闭

[root@youxi1 ~]# systemctl stop mysqld

  之后前往youxi2和youxi3查看谁是主服务器

mysql> show variables like '%read_only%';  //这是youxi2的
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | ON    |
| super_read_only       | ON    |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.01 sec)

mysql> show variables like '%read_only%';  //这是youxi3的
+-----------------------+-------+
| 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 (0.02 sec)

  可以看到youxi3变成了主服务器,那么尝试在youxi3中插入数据

mysql> insert into test_db.user_tb values(2,'lisi');
Query OK, 1 row affected (0.14 sec)

  再到youxi2中查看数据

mysql> select * from test_db.user_tb;    
+----+----------+
| id | name     |
+----+----------+
|  1 | zhangsan |
|  2 | lisi     |
+----+----------+
2 rows in set (0.00 sec)

(2).多主模式

1)在创建时就启用多主模式

  在创建时就启用多主模式只需在修改配置文件/etc/my.cnf时多加两行参数。其余保持不变

loose-group_replication_single_primary_mode=off  //关闭单master模式
loose-group_replication_enforce_update_everywhere_checks=ON  //多主一致性检查

2)由单主模式改为多主模式

  由单主改为多主时,一样需要所有服务器配置信息增加两行参数,为了下次开启就是多主模式

loose-group_replication_single_primary_mode=off  //关闭单master模式
loose-group_replication_enforce_update_everywhere_checks=ON  //开启多主一致性检查

  然后全部服务器停止组复制(GROUP_REPLICATION)集群,并设置参数

mysql> stop GROUP_REPLICATION;
Query OK, 0 rows affected (9.51 sec)

mysql> set global group_replication_single_primary_mode=off;  //关闭单主模式
Query OK, 0 rows affected (0.00 sec)

mysql> set global group_replication_enforce_update_everywhere_checks=ON;  //开启多主一致性检查
Query OK, 0 rows affected (0.00 sec)

  选择其中一台引导组复制(GROUP_REPLICATION)集群

mysql> SET GLOBAL group_replication_bootstrap_group=ON;
Query OK, 0 rows affected (0.00 sec)

mysql> START GROUP_REPLICATION;
Query OK, 0 rows affected (2.13 sec)

mysql> SET GLOBAL group_replication_bootstrap_group=OFF;
Query OK, 0 rows affected (0.01 sec)

  剩下的开启组复制(GROUP_REPLICATION)即可

mysql> start group_replication;
Query OK, 0 rows affected, 1 warning (6.05 sec)

  最后查看非引导组复制的服务器

mysql> select * from performance_schema.replication_group_members;
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 74df3399-91b8-11e9-be5f-000c299fdf40 | youxi3      |        3306 | ONLINE       |
| group_replication_applier | 8fbf8b41-84fe-11e9-897e-000c29f27e52 | youxi2      |        3306 | ONLINE       |
| group_replication_applier | c9e3662b-9020-11e9-94aa-000c29721e89 | youxi1      |        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)

(3).如果宕机了

  停掉youxi1的mysqld模拟宕机

[root@youxi1 ~]# systemctl stop mysqld

  这时候查看youxi2和youxi3谁是新的master

[root@youxi2 ~]# mysql -uroot -p123456
mysql> show variables like '%read_only%';  //这是youxi2的
+-----------------------+-------+
| Variable_name         | Value |
+-----------------------+-------+
| innodb_read_only      | OFF   |
| read_only             | ON    |
| super_read_only       | ON    |
| transaction_read_only | OFF   |
| tx_read_only          | OFF   |
+-----------------------+-------+
5 rows in set (0.00 sec)

[root@youxi3 ~]# mysql -uroot -p123456
mysql> show variables like '%read_only%';  //这是youxi3的,可以看出youxi3成为了新的master
+-----------------------+-------+
| 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 (0.00 sec)

  在youxi3上写入数据,这是因为生产环境数据库是一直在使用的状态,不可能等你修复后再用

[root@youxi3 ~]# mysql -uroot -p123456
mysql> insert into test_db.user_tb values(2,'lisi');
Query OK, 1 row affected (0.03 sec)

mysql> select * from test_db.user_tb;
+----+----------+
| id | name     |
+----+----------+
|  1 | zhangsan |
|  2 | lisi     |
+----+----------+
2 rows in set (0.00 sec)

  将修好的youxi1添加回复制组

[root@youxi1 ~]# systemctl start mysqld
[root@youxi1 ~]# mysql -uroot -p123456
mysql> select * from performance_schema.replication_group_members;
+---------------------------+-----------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+-----------+-------------+-------------+--------------+
| group_replication_applier |           |             |        NULL | OFFLINE      |
+---------------------------+-----------+-------------+-------------+--------------+
1 row in set (0.00 sec)

mysql> change master to master_user='repl',master_password='12345678' for channel 'group_replication_recovery';  //这一步是为了以防万一,
Query OK, 0 rows affected, 2 warnings (0.01 sec)

mysql> set global group_replication_allow_local_disjoint_gtids_join=ON;  //将这台服务器重新添加进复制组
Query OK, 0 rows affected (0.00 sec)

mysql> start group_replication;
Query OK, 0 rows affected (3.36 sec)

mysql> select * from performance_schema.replication_group_members;  //查看是否加入复制组
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| CHANNEL_NAME              | MEMBER_ID                            | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
| group_replication_applier | 07c6f159-964f-11e9-b2c7-000c2934a723 | youxi3      |        3306 | ONLINE       |
| group_replication_applier | 8247f048-962f-11e9-a210-000c2975fa5d | youxi2      |        3306 | ONLINE       |
| group_replication_applier | 8b703193-962a-11e9-b582-000c29e6d627 | youxi1      |        3306 | ONLINE       |
+---------------------------+--------------------------------------+-------------+-------------+--------------+
3 rows in set (0.00 sec)

mysql> select * from test_db.user_tb;  //查看是否同步数据,没有同步请耐心等待,时间可能会长点
+----+----------+
| id | name     |
+----+----------+
|  1 | zhangsan |
|  2 | lisi     |
+----+----------+
2 rows in set (0.00 sec)

  

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