多源複製就是多個master複製，允許一個slave對應多個master；
change master語法（參考：http://dev.mysql.com/doc/refman/5.7/en/change-master-to.html）：
CHANGE MASTER TO option [, option] ... [ channel_option ]
option:
MASTER_BIND = 'interface_name'
| MASTER_HOST = 'host_name'
| MASTER_USER = 'user_name'
| MASTER_PASSWORD = 'password'
| MASTER_PORT = port_num
| MASTER_CONNECT_RETRY = interval
| MASTER_RETRY_COUNT = count
| MASTER_DELAY = interval
| MASTER_HEARTBEAT_PERIOD = interval
| MASTER_LOG_FILE = 'master_log_name'
| MASTER_LOG_POS = master_log_pos
| MASTER_AUTO_POSITION = {0|1}
| RELAY_LOG_FILE = 'relay_log_name'
| RELAY_LOG_POS = relay_log_pos
| MASTER_SSL = {0|1}
| MASTER_SSL_CA = 'ca_file_name'
| MASTER_SSL_CAPATH = 'ca_directory_name'
| MASTER_SSL_CERT = 'cert_file_name'
| MASTER_SSL_CRL = 'crl_file_name'
| MASTER_SSL_CRLPATH = 'crl_directory_name'
| MASTER_SSL_KEY = 'key_file_name'
| MASTER_SSL_CIPHER = 'cipher_list'
| MASTER_SSL_VERIFY_SERVER_CERT = {0|1}
| MASTER_TLS_VERSION = 'protocol_list'
| IGNORE_SERVER_IDS = (server_id_list)
channel_option:
FOR CHANNEL channelserver_id_list:
[server_id [, server_id] ... ]一、環境配置
master 192.168.0.109
master 192.168.0.112
slave 192.168.0.110
確保都開啓gtid_mode，基於事務的複製。配置如下：
[mysqld]
gtid-mode=on
enforce-gtid-consistency=true
避免relay.info更新不及時，SLAVE 重啓後導致的主從複製出錯，，在從服務器上實現事故安全功能，增加配置：
master_info_repository=TABLE
relay_log_info_repository=TABLE
對於多源複製是必須的不然會出現錯誤：
ERROR 3077 (HY000): To have multiple channels, repository cannot be of type FILE; Please check the repository configuration and convert them to TABLE.
查看：show variables like 'gtid_mode';
二、配置步驟
1.在master創建複製用戶。
mysql>create user 'repltest'@'192.168.0.%' identified by 'Repltest123#@!';
mysql>grant replication slave on *.* to 'repltest'@'192.168.0.%';
2.在slave配置change master
change master to master_host='192.168.0.109',
master_user='repltest',
master_password='Repltest123#@!',
master_auto_position=1 FOR CHANNEL 'channe1';
啓動複製 start slave FOR CHANNEL 'channe1';
change master to master_host='192.168.0.112',
master_user='repltest',
master_password='Repltest123#@!',
MASTER_AUTO_POSITION=1 FOR CHANNEL 'channe2';
啓動複製 start slave FOR CHANNEL 'channe2';
可以通過show slave status \G查看複製狀態。如果同步相同庫，同一張表，需要處理，庫和表創建衝突以及，表主鍵衝突情況。
3.可以查看performance_schema下的複製表變化
show tables like 'replication%';
另外可以通過如下全局參數設置多線程複製，提高複製速度：
在slave服務器上停止所有鏈路的複製
stop slave [for channel 'channel']
set global slave_parallel_type='logical_clock' 併發類型， 默認DATABASE
set global slave_parallel_workers=4 併發工作線程數 默認爲0
start slave [for channel 'channel']
重新啓動複製鏈接。
通過查看線程數：
show processlist;
查詢系統視圖的變化：
replication_applier_status_by_coordinator 協調複製線程
replication_applier_status_by_worker 複製線程的工作狀態
參考文章：
