背景：
MySQL5.7在主从复制上面相对之前版本多了一些新特性，包括多源复制、基于组提交的并行复制、在线修改Replication Filter、GTID增强、半同步复制增强等。因为都是和复制相关，所以本文将针对这些新特性放一起进行说明，篇幅可能稍长，本文使用的MySQL版本是5.7.13。
1，多源复制（多主一从）
MySQL在5.7之后才支持多源复制，之前介绍过官方文档。
原理：多源复制加入了一个叫做Channel的概念， 每一个Channel都是一个独立的Slave，都有一个IO_THREAD和SQL_THREAD。原理和普通复制一样。我们只需要对每一个Master执行Change Master 语句，只需要在每个语句最后使用For Channel来进行区分。由于复制的原理没有改变，在没有开启GTID的时候Master的版本可以是MySQL5.5、5.6、5.7。并且从库需要master-info-repository、relay-log-info-repository设置为table，否则会报错：
ERROR 3077 (HY000): To have multiple channels, repository cannot be of type FILE; Please check the repository configuration and convert them to TABLE.
① 测试环境：
5台主机（1从4主）：
MySQL5.5 : 10.0.3.202 MySQL5.6 : 10.0.3.162 MySQL5.7 : 10.0.3.141 MySQL5.7 : 10.0.3.219 MySQL5.7 : 10.0.3.251
② 复制账号：
mysql> CREATE USER 'repl'@'10.0.3.%' IDENTIFIED BY 'Repl_123456'; Query OK, 0 rows affected (0.00 sec) mysql> GRANT REPLICATION SLAVE ON *.* TO 'repl'@'10.0.3.%'; Query OK, 0 rows affected (0.00 sec)
③ Change：这里先说明通过binlog文件名和position的普通复制，后面会专门介绍GTID的复制。10.0.3.251（MySQL5.7）做从库，这里需要注意：从的版本若是5.7.x～5.7.13，主的版本不能是MySQL5.5，因为MySQL5.5没有server_uuid函数。该问题在MySQL5.7.13里修复(Bug #22748612)。
CHANGE MASTER TO MASTER_HOST='10.0.3.141',MASTER_USER='repl',MASTER_PASSWORD='Repl_123456',MASTER_LOG_FILE='mysql-bin-3306.000001',MASTER_LOG_POS=154 FOR CHANNEL 't22'; CHANGE MASTER TO MASTER_HOST='10.0.3.162',MASTER_USER='repl',MASTER_PASSWORD='Repl_123456',MASTER_LOG_FILE='mysql-bin.000001',MASTER_LOG_POS=120 FOR CHANNEL 't21'; CHANGE MASTER TO MASTER_HOST='10.0.3.202',MASTER_USER='repl',MASTER_PASSWORD='Repl_123456',MASTER_LOG_FILE='mysql-bin-3306.000001',MASTER_LOG_POS=107 FOR CHANNEL 't10'; CHANGE MASTER TO MASTER_HOST='10.0.3.219',MASTER_USER='repl',MASTER_PASSWORD='Repl_123456',MASTER_LOG_FILE='mysql-bin-3306.000001',MASTER_LOG_POS=154 FOR CHANNEL 't23';
④ 相关操作：
查看单个channel的状态：
show slave status for channel 't10'\G
停止单个channel的同步：
stop slave for channel 't10';
开启单个channel的同步：
start slave for channel 't10';
重置单个channel：
reset slave all for channel 't10';
查看所有channel：
show slave status\G
停止所有channel：
stop slave;
开启所有channel：
start slave;
跳过一个channel的报错（类似MariaDB的default_master_connection）：
channel 't10' 报错： mysql> show slave status for channel 't10'\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 10.0.3.202 Master_User: repl Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin-3306.000001 Read_Master_Log_Pos: 827 Relay_Log_File: mysqld-relay-bin-t10.000006 Relay_Log_Pos: 767 Relay_Master_Log_File: mysql-bin-3306.000001 Slave_IO_Running: Yes Slave_SQL_Running: No Replicate_Do_DB: Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 1062 Last_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 0 failed executing transaction 'ANONYMOUS' at master log mysql-bin-3306.000001, end_log_pos 800. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Skip_Counter: 0 Exec_Master_Log_Pos: 646 Relay_Log_Space: 1303 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: NULL Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 1062 Last_SQL_Error: Coordinator stopped because there were error(s) in the worker(s). The most recent failure being: Worker 0 failed executing transaction 'ANONYMOUS' at master log mysql-bin-3306.000001, end_log_pos 800. See error log and/or performance_schema.replication_applier_status_by_worker table for more details about this failure or others, if any. Replicate_Ignore_Server_Ids: Master_Server_Id: 5 Master_UUID: Master_Info_File: mysql.slave_master_info SQL_Delay: 0 SQL_Remaining_Delay: NULL Slave_SQL_Running_State: Master_Retry_Count: 86400 Master_Bind: Last_IO_Error_Timestamp: Last_SQL_Error_Timestamp: 160725 19:10:08 Master_SSL_Crl: Master_SSL_Crlpath: Retrieved_Gtid_Set: Executed_Gtid_Set: Auto_Position: 0 Replicate_Rewrite_DB: Channel_Name: t10 Master_TLS_Version: