上一篇我们将mgr多主集群切换到单主模式，实现了一主(master)两备(secondary)的架构。在高并发模式下，paxos协议的乐观锁可能会导致事务的冲突、回滚和性能的下降，这次我们尝试通过中间件atlas的方式，实现读写分离的架构。
atlas是360团队在MySQL-Proxy 0.8.2版本的基础上，进一步优化的项目，该中间件在当前很多场景中得到广泛应用。 这里将atlas部署在Node3服务器上，通过atlas实现数据库的读写分离。
1、部署atlas软件在node3节点，并进行参数的配置
#####安装atlas软包
rpm -ivh Atlas-2.2.1.el6.x86_64.rpm
#####配置atlas配置文件
cd /usr/local/mysql-proxy/conf
mv test.cnf test.cnfbak####编辑配置文件，填写下列配置
vi test.cnf[mysql-proxy]
proxy-backend-addresses = 192.168.170.17:3306
proxy-read-only-backend-addresses = 192.168.170.18:3306,192.168.170.19:3306
pwds = xhh:/iZxz+0GRoA=,mha:/iZxz+0GRoA=
daemon = true
keepalive = true
event-threads = 8
log-level = message
log-path = /usr/local/mysql-proxy/log
sql-log=ON
proxy-address = 0.0.0.0:33060
admin-username = user
admin-password = pass
admin-address = 0.0.0.0:12345
charset=utf8 #####关键参数说明
#####proxy-backend-addresses 主库的写节点
#####proxy-read-only-backend-addresses 读写点
#####pwds 应用连接的用户和加密密码
#####daemon 以后台的方式运行
#####keepalive 心跳检测
#####event-threads 开启的线程
#####proxy-address 对外提供服务的代理地址
#####admin-address 内部管理地址
#####admin-username、admin-password 内部管理的用户名和密码2、启动atlas服务
[root@rac3 ~]# cd /usr/local/mysql-proxy/bin
[root@rac3 bin]# ls
encrypt mysql-proxy mysql-proxyd VERSION
[root@rac3 bin]# #####encrypt 制作加密的
[root@rac3 bin]# ./encrypt 123456
/iZxz+0GRoA=#####mysql-proxyd atlas的启动进程[root@rac3 bin]# ./mysql-proxyd test start
OK: MySQL-Proxy of test is started
[root@rac3 bin]#3、测试atlas读写分离
#####通过atlas代理地址连接mgr集群
[root@rac3 bin]# /usr/local/mysql/bin/mysql -uxhh -p123456 -P13306 -h192.168.170.19
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.81-log MySQL Community Server (GPL)
Copyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> select @@server_id;
+-------------+
| @@server_id |
+-------------+
| 3 |
+-------------+
1 row in set (0.00 sec)
mysql> select @@server_id;
+-------------+
| @@server_id |
+-------------+
| 2 |
+-------------+
1 row in set (0.00 sec)
mysql>
#####atlas分别将查询的请求分别发到节点2和节点3进行处理#####atlas将写的请求发送到节点1进行处理
mysql> begin;select @@server_id;commit;
Query OK, 0 rows affected (0.01 sec)
+-------------+
| @@server_id |
+-------------+
| 1 |
+-------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
mysql>
4、atlas端口管理
#####通过配置文件定义用户名和密码连接到atlas内置库，可进行一些节点管理等操作
[root@rac3 bin]# /usr/local/mysql/bin/mysql -uuser -ppass -P12345 -h192.168.170.19
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.99-agent-adminCopyright (c) 2000, 2020, Oracle and/or its affiliates. All rights reserved.Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.mysql> select * from help;
+----------------------------+---------------------------------------------------------+
| command | description |
+----------------------------+---------------------------------------------------------+
| SELECT * FROM help | shows this help |
| SELECT * FROM backends | lists the backends and their state |
| SET OFFLINE $backend_id | offline backend server, $backend_id is backend_ndx's id |
| SET ONLINE $backend_id | online backend server, ... |
| ADD MASTER $backend | example: "add master 127.0.0.1:3306", ... |
| ADD SLAVE $backend | example: "add slave 127.0.0.1:3306", ... |
| REMOVE BACKEND $backend_id | example: "remove backend 1", ... |
| SELECT * FROM clients | lists the clients |
| ADD CLIENT $client | example: "add client 192.168.1.2", ... |
| REMOVE CLIENT $client | example: "remove client 192.168.1.2", ... |
| SELECT * FROM pwds | lists the pwds |
| ADD PWD $pwd | example: "add pwd user:raw_password", ... |
| ADD ENPWD $pwd | example: "add enpwd user:encrypted_password", ... |
| REMOVE PWD $pwd | example: "remove pwd user", ... |
| SAVE CONFIG | save the backends to config file |
| SELECT VERSION | display the version of Atlas |
+----------------------------+---------------------------------------------------------+
16 rows in set (0.00 sec)mysql>
mysql> select * from backends;
+-------------+---------------------+-------+------+
| backend_ndx | address | state | type |
+-------------+---------------------+-------+------+
| 1 | 192.168.170.17:3306 | up | rw |
| 2 | 192.168.170.18:3306 | up | ro |
| 3 | 192.168.170.19:3306 | up | ro |
+-------------+---------------------+-------+------+
3 rows in set (0.00 sec)
mysql>
####通过backends可以查询到后端的节点，type状态为读写、读等通过atlas+mgr实现了读写分离，但如果主节点发生切换，需要手动修改atlas的配置来实现业务的耦合，在一些7*24小时的应用场景不太符合业务实时性的要求，下篇我们将通过虚拟地址的方式来解决这一问题。