一、 简介
Cetus是由C语言开发的关系型数据库MySQL的中间件，主要提供了一个全面的数据库访问代理功能。Cetus连接方式与MySQL基本兼容，应用程序几乎不用修改即可通过Cetus访问数据库，实现了数据库层的水平扩展和高可用。
Cetus由网易乐得专家技术团队领队，经多部门协调合作设计出来的优秀中间件。
具体详细可参考官网：https://github.com/Lede-Inc/cetus
本文主要基于读写分离的实践
二、 读写分离的搭建
1、安装依赖
yum install cmake gcc glib2-devel flex libevent-devel mysql-devel gperftools-libs -y
2、下载源码
git clone https://github.com/Lede-Inc/cetus.git
3、编译安装
1、在源码主目录下创建独立的目录build，并转到该目录下
mkdir build/
cd build/
2、编译：利用cmake进行编译，指令如下
cmake ../ -DCMAKE_BUILD_TYPE=Debug -DCMAKE_INSTALL_PREFIX=/data/cetus/cetus_install -DSIMPLE_PARSER=ON
3、安装：执行make install进行安装
make install
4、配置文件
cd /data/cetus/cetus_install/conf/
cp XXX.json.example XXX.json
cp XXX.conf.example XXX.conf
vi XXX.json
vi XXX.conf
本文基于读写分离主要配置两个文件users.json和proxy.conf
1、cp users.json.example users.json && vim users.json
{
"users": [{
"user": "root",
"client_pwd": "123",
"server_pwd": "123456"
}]
}
2、cp proxy.conf.example proxy.conf && vim proxy.conf
[cetus]
# For mode-switch
daemon = true
# Loaded Plugins
plugins=proxy,admin
# Proxy Configuration, For eaxmlpe: MySQL master and salve host ip are both 192.0.0.1
proxy-address=127.0.0.1:6001
proxy-backend-addresses=192.168.142.48:5700
proxy-read-only-backend-addresses=192.168.142.49:5700
# Admin Configuration
admin-address=127.0.0.1:7001
admin-username=admin
admin-password=admin
# Backend Configuration, use test db and username created
default-db=test
default-username=root
# File and Log Configuration, put log in /data and marked by proxy port, /data/cetus needs to be created manually and has rw authority for cetus os user
pid-file = cetus6001.pid
plugin-dir=lib/cetus/plugins
log-file=cetus_6001.log
log-level=debug
# support the MGR
group-replication-mode = 1
5、启动
./bin/cetus --defaults-file=conf/proxy.conf --conf-dir=/data/cetus/cetus_install/conf/
6、命令行登录
1、应用端口
usr/local/mysql-5.7.18/bin/mysql --prompt="proxy> " --comments -uroot -p123 -h227.0.0.1 -P6001
proxy> select version();
+------------+
| version() |
+------------+
| 5.7.18-log |
+------------+
1 row in set (0.00 sec)
2、管理端口
/usr/local/mysql-5.7.18/bin/mysql --prompt="admin> " --comments -uadmin -padmin -h227.0.0.1 -P7001
admin> select * from backends;
+-------------+--------------------+-------+------+-------------+------+------------+------------+-------------+
| backend_ndx | address | state | type | slave delay | uuid | idle_conns | used_conns | total_conns |
+-------------+--------------------+-------+------+-------------+------+------------+------------+-------------+
| 1 | 192.168.142.48:5700 | up | rw | NULL | NULL | 2 | 0 | 2 |
| 2 | 192.168.142.49:5700 | up | ro | 0 | NULL | 2 | 0 | 2 |
+-------------+--------------------+-------+------+-------------+------+------------+------------+-------------+
2 rows in set (0.00 sec)
三、 MGR的读写分离测试
部署环境
MGR环境
192.168.142.48为MGR主节点
192.168.142.49为MGR从节点
写入节点配置
proxy-backend-addresses=192.168.142.48:5700
读取节点配置
proxy-read-only-backend-addresses=192.168.142.49:5700
1、测试读：
1.1、主从组复制正常
proxy> select sleep(15) from t1 where a=1;
192.168.142.49上出现对应读请求进程
1.2、主从组复制异常
192.168.142.49停止组复制
root@192.168.142.49> STOP GROUP_REPLICATION;
proxy> select sleep(15) from t1 where a=1;
192.168.142.48上出现对应读请求进程
2、测试写：
2.1、主从组复制正常
proxy> insert into t1 select 6, sleep(15);
192.168.142.48上出现对应写请求进程
2.2、主从组复制异常
192.168.142.49停止组复制
root@192.168.142.49> STOP GROUP_REPLICATION;
proxy> insert into t1 select 7, sleep(15);
192.168.142.48上出现对应写请求进程
四、 一主两从的读写分离测试
部署环境
192.168.142.48为master节点
192.168.142.49为slave节点
192.168.142.50为slave节点
写入节点配置
proxy-backend-addresses=192.168.142.48:5700
读取节点配置
proxy-read-only-backend-addresses=192.168.142.49:5700,192.168.142.50:5700
1、测试读：
proxy> select sleep(15) from t1 where a=1;
192.168.142.49上出现对应读请求进程
再次读请求
proxy> select sleep(15) from t1 where a=1;
192.168.142.50上出现对应读请求进程
可以发现读请求是均匀随机到两个读节点
2、测试写：
proxy> insert into t1 select 2 ,sleep(15);
192.168.142.48上出现对应写请求进程
