在>=mysql5.7.17的版本中开始支持组复制插件。组复制中的成员至少需要三个才会起到容错作用，各成员在通信层通过原子广播及总订单消息的
传递一起应用或回滚事务组从而达到数据的强一致性。组复制的成员是独立处理事务的，rw事务需要通过组的冲突检查才可以进行，ro事务则不需要
组之间的通信而直接提交。当一个成员要提交rw事务时，会原子广播写入的行数据和相关的写入集（变更行的唯一身份认证标志），所有的成员会接
收到一组顺序相同的事务集并顺序应用。如果不同的两组事务同时并发在两个成员上修改相同的行记录，那么这就是冲突（通过事务集的唯一标识值来
检测冲突），这种情况下，遵循第一提交完胜的准则。
组复制协议
组复制实践
单主机部署三个实例，端口分别为
s1：6666
s2：6667
s3：6668
与组复制相关的参数配置
server_id=1 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="aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa" loose-group_replication_start_on_boot=off loose-group_replication_local_address= "127.0.0.1:10001" loose-group_replication_group_seeds= "127.0.0.1:10001,127.0.0.1:10002,127.0.0.1:10003" loose-group_replication_bootstrap_group= off
10001、10002、10003是每个实例的recovery process分别侦听的端口
如果开启并行复制 还需 slave_preserve_commit_order 设置为1
先部署s1
1、创建用于复制事务日志的用户
组复制基于binlog采用异步复制的协议，recovery process通过group_replication_recovery 通道在成员间传输事务日志，
复制用户要有 REPLICATION SLAVE 权限
注意创建用户的日志不可以到达其他的成员实例上
set sql_log_bin=0;GRANT REPLICATION SLAVE ON *.* TO grepl@'%' IDENTIFIED BY 'grepl'; flush privileges;set sql_log_bin=1;
配置恢复通道用于从其他成员复制恢复
mysql> CHANGE MASTER TO MASTER_USER='grepl', MASTER_PASSWORD='grepl' FOR CHANNEL 'group_replication_recovery'; Query OK, 0 rows affected, 2 warnings (0.02 sec)
安装组复制插件
mysql> INSTALL PLUGIN group_replication SONAME 'group_replication.so'; Query OK, 0 rows affected (0.10 sec)
# check
mysql> show plugins;
开启组复制
通过s1引导组（bootstrap group）并开启组复制，bootstrap group只可以进行一次并由一个成员进行，不把 group_replication_bootstrap_group=ON
放到配置文件中的原因是避免实例重启重新进行bootstrap group，若果重复执行，则会产生两个拥有相同成员的组。
SET GLOBAL group_replication_bootstrap_group=ON; START GROUP_REPLICATION; SET GLOBAL group_replication_bootstrap_group=OFF;
mysql> SELECT * FROM performance_schema.replication_group_members;
+---------------------------+--------------------------------------+----------------+-------------+--------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE |
+---------------------------+--------------------------------------+----------------+-------------+--------------+
| group_replication_applier | b110f16d-3163-11e7-b64a-fa163eef641d | 10.211.253.192 | 6666 | ONLINE |
+---------------------------+--------------------------------------+----------------+-------------+--------------+
1 row in set (0.00 sec)
MEMBER_HOST字段显示的是report_host 的值
创建测试数据
use test CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL); INSERT INTO t1 VALUES (1, 'Luis');
SELECT * FROM t1;
mysql> SHOW BINLOG EVENTS in 'mysql-bin.000002';
+------------------+-----+----------------+------------+-------------+--------------------------------------------------------------------+
| Log_name | Pos | Event_type | Server_id | End_log_pos | Info |
+------------------+-----+----------------+------------+-------------+--------------------------------------------------------------------+
| mysql-bin.000002 | 4 | Format_desc | 4294967295 | 123 | Server ver: 5.7.18-log, Binlog ver: 4 |
| mysql-bin.000002 | 123 | Previous_gtids | 4294967295 | 150 | |
| mysql-bin.000002 | 150 | Gtid | 4294967295 | 211 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:1' |
| mysql-bin.000002 | 211 | Query | 4294967295 | 270 | BEGIN |
| mysql-bin.000002 | 270 | View_change | 4294967295 | 369 | view_id=14939720086383376:1 |
| mysql-bin.000002 | 369 | Query | 4294967295 | 434 | COMMIT |
| mysql-bin.000002 | 434 | Gtid | 4294967295 | 495 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:2' |
| mysql-bin.000002 | 495 | Query | 4294967295 | 585 | CREATE DATABASE test |
| mysql-bin.000002 | 585 | Gtid | 4294967295 | 646 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:3' |
| mysql-bin.000002 | 646 | Query | 4294967295 | 770 | use `test`; CREATE TABLE t1 (c1 INT PRIMARY KEY, c2 TEXT NOT NULL) |
| mysql-bin.000002 | 770 | Gtid | 4294967295 | 831 | SET @@SESSION.GTID_NEXT= 'aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa:4' |
| mysql-bin.000002 | 831 | Query | 4294967295 | 899 | BEGIN |
| mysql-bin.000002 | 899 | Table_map | 4294967295 | 942 | table_id: 219 (test.t1) |
| mysql-bin.000002 | 942 | Write_rows | 4294967295 | 984 | table_id: 219 flags: STMT_END_F |
| mysql-bin.000002 | 984 | Xid | 4294967295 | 1011 | COMMIT /* xid=73 */ |
+------------------+-----+----------------+------------+-------------+--------------------------------------------------------------------+
15 rows in set (0.01 sec)
添加组成员
重复上上面的操作，除了设置group_replication_bootstrap_group，注意个别配置项的更改
mysql> select * FROM performance_schema.replication_group_members; +---------------------------+--------------------------------------+----------------+-------------+--------------+ | CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | +---------------------------+--------------------------------------+----------------+-------------+--------------+ | group_replication_applier | b110f16d-3163-11e7-b64a-fa163eef641d | 10.211.253.192 | 6666 | ONLINE | | group_replication_applier | b9e9924f-3163-11e7-b226-fa163eef641d | 10.211.253.192 | 6667 | ONLINE | | group_replication_applier | c1ae8a71-3163-11e7-ad97-fa163eef641d | 10.211.253.192 | 6668 | ONLINE | +---------------------------+--------------------------------------+----------------+-------------+--------------+ 3 rows in set (0.00 sec)
其他的成员加入组aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa后在被宣布online前自动复制s1的差异日志并应用
组复制模式
https://dev.mysql.com/doc/refman/5.7/en/group-replication-deploying-in-multi-primary-or-single-primary-mode.html