RDS数据库与自建库的gtid主从同步，什么是主从数据库
场景：数据库用的是和通数据库的RDS，有个实时数据分析项目需要做数据库主从，开始的时候购买了和通数据库RDS的只读实例，但在测试的过程中，发现该只读实例不能满足项目需求。因为实时数据分析项目需要从库的条件有：
1、从库需要有开启和停止主从的权限；
2、从库需要支持replication级联同步。
经咨询和通数据库工程师，只能通过DTS进行数据同步，并且不支持级联同步。所以只好自己搭建MYSQL主从去满足项目了。
一、在centos7上部署MySQL数据库
1、从MYSQL官网下载安装文件
wget http://dev.mysql.com/get/mysql-community-release-el7-5.noarch.rpm
2、卸载mariadb
rpm -qa | grep mariadb #查询已安装的mariadb rpm
rpm -e --nodeps mariadb-libs-xxxxx.x86_64 #强制卸载
3、安装MySQL
rpm -ivh mysql-community-release-el7-5.noarch.rpm
yum install mysql-community-server
4、启动MySQL
systemctl start mysqld.service
5、停止MySQL
systemctl stop mysqld.service
二、修改从库配置文件/etc/my.cnf
character-set-server=utf8
datadir = /var/lib/mysql
socket = /var/lib/mysql/mysql.sock
wait_timeout=2880000
interactive_timeout = 2880000
max_allowed_packet = 100M
innodb_checksum_algorithm=innodb
innodb_data_file_path=ibdata1:200M:autoextend
innodb_log_files_in_group=2
innodb_log_file_size=524288000
innodb_undo_directory=.
innodb_undo_tablespaces=0
server-id = 10000
gtid_mode = on
enforce_gtid_consistency = 1
master-info-repository = file
relay-log-info_repository = file
log-bin = mysqlslave-bin
relay-log = mysqlslave-relay-bin
expire_logs_days = 30
log-slave-updates = 1
binlog_format = row
replicate-do-db = db1
replicate-do-db = db2
replicate-do-db = db3
replicate-ignore-db = mysql
replicate-ignore-db = information_schema
replicate-ignore-db = performance_schema
slave-skip-errors = 1007,1008,1053,1062,1213,1158,1159
三、重启从库
systemctl restart mysqld.service
四、从RDS的数据库导数据出来
mysqldump -u db1_user -pdb1_password -hmasterhost.mysql.rds.aliyuncs.com> /tmp/db1.sql
mysqldump -u db2_user -pdb2_password -hmasterhost.mysql.rds.aliyuncs.com> /tmp/db2.sql
mysqldump -u db3_user -pdb3_password -hmasterhost.mysql.rds.aliyuncs.com> /tmp/db3.sql
五、主库查询master gtid_purged
mysql>show global variables like '%gtid%';
找到gtid_purged的值，第七步要用到
六、将RDS导出的数据库，导入到从库
mysql -uroot -p root_password < /tmp/db1.sql
mysql -uroot -p root_password < /tmp/db2.sql
mysql -uroot -p root_password < /tmp/db3.sql
七、进入从库，设置同步信息
mysql>reset master;
mysql>set @@global.gtid_purged='主库的GITD值';
mysql>change master to master_host = 'masterhost.mysql.rds.aliyuncs.com', master_port = 3306, master_user = 'repl', master_password='repl_password', master_auto_position = 1;
mysql>start slave;
八、查询返回信息
mysql>show slave status G;
Slave_IO_Running: Yes
Slave_SQL_Running: Yes
两个都是yes，表示同步成功。