通常一个网站在初期访问量都比较小，所以一般的小架构足以支撑。但是，当网站逐渐发展起来后，随之而来的是大量的访问，这时候最先出现的瓶颈就是数据库了。因为数据的写入读取操作（I/O）是集群中响应速度最慢的，所以在集群建设时就要规划好后端存储架构。
后端存储数据库架构普遍是主从复制，这样解决了数据备份问题。但是，由前端来的读写请求都要经过主库，量小没问题，当量大到超过主库的性能极限时，主库分分钟会宕机。
为了避免主库宕机这种灾难性事件的发生，读写分离的设计诞生了！把写的请求只交给主库，读的请求由主库和从库一起分摊，这样就大大减轻了主库的负担。
大部分公司会由开发部门在软件层面实现对数据库的读写分离，其次可以选择读写分离的中间件如：TDDL、amoeba、cobar、MySQL-proxy、Atlas、MyCat。
本次测试采用MySQL官方发布的MySQL-proxy。
官网下载地址（二进制包）：https://downloads.mysql.com/archives/get/file/mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz
测试环境：
[[email protected] ~]# cat /etc/redhat-release
CentOS release 6.8 (Final)
[[email protected] ~]# uname -r
2.6.32-642.el6.x86_64
MySQL-proxy IP：192.168.0.86
MySQL-master IP：192.168.0.88
MySQL-slave IP：192.168.0.90
前提：MySQL主库与从库已经实现主从复制。
实现主从复制请参考我的前一篇博文：http://yuyicong.blog.51cto.com/11274530/1919158
接下来的操作在proxy服务器上：
[[email protected] ~]# cd /usr/local/src/
[[email protected] src]# wget https://downloads.mysql.com/archives/get/file/mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz
[[email protected] src]# ll -h
total 12M
-rw-r--r-- 1 root root 12M Aug 19 2014 mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz
[[email protected] src]# tar zxf mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz -C /usr/local/
[[email protected] src]# cd ..
[[email protected] local]# mv mysql-proxy-0.8.5-linux-el6-x86-64bit/ mysql-proxy-0.8.5
[[email protected] local]# ll -d mysql-proxy-0.8.5
drwxr-xr-x 8 7161 wheel 4096 Aug 19 2014 mysql-proxy-0.8.5 # 看到所属用户和组有问题
[[email protected] local]# chown -R root:root mysql-proxy-0.8.5/ # 改为root
[[email protected] local]# ln -s mysql-proxy-0.8.5/ mysql-proxy # 必备软连接
[[email protected] local]# cd mysql-proxy
[[email protected] mysql-proxy]# mkdir etc # 创建 lua 脚本存放目录
[[email protected] mysql-proxy]# mkdir logs # 创建日志目录
把实现读写分离的 lua 脚本复制到 etc 目录下
[[email protected] mysql-proxy]# cp share/doc/mysql-proxy/rw-splitting.lua etc/
[[email protected] mysql-proxy]# cp share/doc/mysql-proxy/admin-sql.lua etc/
创建启动参数文件，启动服务时命令行就不用老长老长的。
[[email protected] ~]# vim /etc/mysql-proxy.cnf
[mysql-proxy] admin-username=proxy # 连接主从mysql共有的用户 admin-password=123 # 连接用户的密码 proxy-address=192.168.0.86:3306 # mysql-proxy监听本地工作ip和端口，不加端口默认是4040，为了方便管理这里用3306 proxy-backend-addresses=192.168.0.87:3306 # 指定后端主库 proxy-read-only-backend-addresses=192.168.0.90:3306 # 指定后端只读从库 proxy-lua-script=/usr/local/mysql-proxy/etc/rw-splitting.lua # 指定实现读写分离的lua脚本 admin-lua-script=/usr/local/mysql-proxy/etc/admin-sql.lua # 指定管理脚本 pid-file=/var/run/mysql-proxy.pid log-file=/usr/local/mysql-proxy/logs/mysql-proxy.log # 日志位置 log-level=info # 定义log日志级别，由高到低分别有(error|warning|info|message|debug) daemon=true # 以守护进程方式运行 keepalive=true # work进程崩溃时，尝试重启
启动服务
[[email protected] ~]# /usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/etc/mysql-proxy.cnf
2017-04-24 16:40:19: (critical) mysql-proxy-cli.c:326: loading config from ‘/etc/mysql-proxy.cnf‘ failed: permissions of /etc/mysql-proxy.cnf aren‘t secure (0660 or stricter required)
2017-04-24 16:40:19: (message) Initiating shutdown, requested from mysql-proxy-cli.c:328
2017-04-24 16:40:19: (message) shutting down normally, exit code is: 1
！！看到无法启动，文件权限要改，因为文件里面有账号密码。
[[email protected] ~]# chmod 660 /etc/mysql-proxy.cnf # 改权限
[[email protected] ~]# ll /etc/mysql-proxy.cnf
-rw-rw---- 1 root root 432 Apr 24 16:31 /etc/mysql-proxy.cnf
[[email protected] ~]# /usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/etc/mysql-proxy.cnf # 重新启动
[[email protected] ~]# netstat -lntup # 查看服务
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 192.168.0.86:3306 0.0.0.0:* LISTEN 3086/mysql-proxy
老是命令行敲一长串命令肯定不科学了，直接上服务管理脚本。
[[email protected] ~]# vim /etc/init.d/mysql-proxy
#!/bin/bash
#
# mysql-proxy This script starts and stops the mysql-proxy daemon
#
# chkconfig: - 78 30
# processname: mysql-proxy
# description: mysql-proxy is a proxy daemon for mysql
# Source function library.
. /etc/rc.d/init.d/functions
prog="/usr/local/mysql-proxy/bin/mysql-proxy"
# Source networking configuration.
if [ -f /etc/sysconfig/network ]; then
. /etc/sysconfig/network
fi
# Check that networking is up.
[ ${NETWORKING} = "no" ] && exit 0
DEFAULT_FILE=/etc/mysql-proxy.cnf
PROXY_PID=/var/run/mysql-proxy.pid
RETVAL=0
start() {
echo -n $"Starting MySQL-proxy... : "
daemon $prog --defaults-file=$DEFAULT_FILE
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
touch /var/lock/subsys/mysql-proxy.lock
fi
}
stop() {
echo -n $"Stopping MySQL-proxy... : "
killproc -p $PROXY_PID -d 3 $prog
RETVAL=$?
echo
if [ $RETVAL -eq 0 ]; then
rm -f /var/lock/subsys/mysql-proxy.lock
rm -f $PROXY_PID
fi
}
# See how we were called.
case "$1" in
start)
start
;;
stop)
stop
;;
restart)
stop
start
;;
condrestart|try-restart)
if status -p $PROXY_PIDFILE $prog >&/dev/null; then
stop
start
fi
;;
status)
status -p $PROXY_PID $prog
;;
*)
echo "Usage: $0 {start|stop|restart|reload|status|condrestart|try-restart}"
RETVAL=1
;;
esac
exit $RETVAL
[[email protected] ~]# chmod +x /etc/init.d/mysql-proxy # 给执行权限
[[email protected] ~]# chkconfig mysql-proxy on # 可以加入开机启动
测试一下脚本：
[[email protected] ~]# /etc/init.d/mysql-proxy status mysql-proxy (pid 3086) is running... [[email protected] ~]# [[email protected] ~]# /etc/init.d/mysql-proxy stop Stopping MySQL-proxy... : [ OK ] [[email protected] ~]# [[email protected] ~]# /etc/init.d/mysql-proxy status mysql-proxy is stopped [[email protected] ~]# netstat -lntup Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 1079/sshd tcp 0 0 :::22 :::* LISTEN 1079/sshd [[email protected] ~]# /etc/init.d/mysql-proxy start Starting MySQL-proxy... : [ OK ] [[email protected] ~]# /etc/init.d/mysql-proxy restart Stopping MySQL-proxy... : [ OK ] Starting MySQL-proxy... : [ OK ] [[email protected] ~]# [[email protected] ~]# netstat -lntup Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 192.168.0.86:3306 0.0.0.0:* LISTEN 3143/mysql-proxy
以上MySQL-proxy服务器搭建完成，但是用于连接后端数据库的用户：proxy还需要在数据库端创建
数据库Master端：创建proxy用户，给增删改查权限
[[email protected] ~]# mysql -uroot -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 3 Server version: 5.5.55-log MySQL Community Server (GPL) Copyright (c) 2000, 2017, 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. Master> Master> grant insert,delete,update,select on *.* to [email protected]‘192.168.0.86‘ identified by ‘123‘; Query OK, 0 rows affected (0.00 sec) Master> select user,host from mysql.user; +-------+--------------+ | user | host | +-------+--------------+ | root | 127.0.0.1 | | rep | 192.168.0.% | | proxy | 192.168.0.86 | | root | localhost | +-------+--------------+ 4 rows in set (0.00 sec) Master> show grants for [email protected]‘192.168.0.86‘; +------------------------------------------------------------------------------------------------------------------------------------------+ | Grants for [email protected] | +------------------------------------------------------------------------------------------------------------------------------------------+ | GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO ‘proxy‘@‘192.168.0.86‘ IDENTIFIED BY PASSWORD ‘*23AE809DDACAF96AF0FD78ED04B6A265E05AA257‘ | +------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
Slave端：此时已经与主库一致拥有了proxy用户，但是从库只能读（select），所以要对proxy回收权限。
Slave> show grants for [email protected]‘192.168.0.86‘; +------------------------------------------------------------------------------------------------------------------------------------------+ | Grants for [email protected] | +------------------------------------------------------------------------------------------------------------------------------------------+ | GRANT SELECT, INSERT, UPDATE, DELETE ON *.* TO ‘proxy‘@‘192.168.0.86‘ IDENTIFIED BY PASSWORD ‘*23AE809DDACAF96AF0FD78ED04B6A265E05AA257‘ | +------------------------------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec) Slave> revoke insert,update,delete on *.* from [email protected]‘192.168.0.86‘; # 只留查询权限 Query OK, 0 rows affected (0.00 sec) Slave> show grants for [email protected]‘192.168.0.86‘; +------------------------------------------------------------------------------------------------------------------+ | Grants for [email protected] | +------------------------------------------------------------------------------------------------------------------+ | GRANT SELECT ON *.* TO ‘proxy‘@‘192.168.0.86‘ IDENTIFIED BY PASSWORD ‘*23AE809DDACAF96AF0FD78ED04B6A265E05AA257‘ | +------------------------------------------------------------------------------------------------------------------+ 1 row in set (0.00 sec)
测试读写分离
为了方便测试，修改 rw-splitting.lua 脚本里触发读写分离参数
[[email protected] ~]# vim /usr/local/mysql-proxy/etc/rw-splitting.lua
-- connection pool
if not proxy.global.config.rwsplit then
proxy.global.config.rwsplit = {
min_idle_connections = 1, # 默认超过4个连接数时，才开始读写分离，改为1
max_idle_connections = 8, # 默认最大连接数8，不动它
is_debug = false
}
end
[[email protected] ~]# /etc/init.d/mysql-proxy restart # 重启一下
Stopping MySQL-proxy... : [ OK ]
Starting MySQL-proxy... : [ OK ]
数据库Master端
Master> create database proxy; # 建个库 Query OK, 1 row affected (0.00 sec) Master> create table master(id int(2),name char(10)); # 停掉从库 IO线程后再建个表 Query OK, 0 rows affected (0.18 sec) Master> desc master; +-------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+---------+-------+ | id | int(2) | YES | | NULL | | | name | char(10) | YES | | NULL | | +-------+----------+------+-----+---------+-------+ 2 rows in set (0.00 sec)
Slave端
Slave> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | proxy | # 新建的库已经有了 | school | | test | +--------------------+ 6 rows in set (0.00 sec) Slave> stop slave io_thread; # 停掉 IO 线程 Query OK, 0 rows affected (0.00 sec) Slave> show slave status\G *************************** 1. row *************************** Slave_IO_State: Master_Host: 192.168.0.88 Master_User: rep Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000019 Read_Master_Log_Pos: 351 Relay_Log_File: relay-bin.000011 Relay_Log_Pos: 497 Relay_Master_Log_File: mysql-bin.000019 Slave_IO_Running: No Slave_SQL_Running: Yes Slave> use proxy; Database changed Slave> create table slave(id int(2),name char(10)); # 建个表 Query OK, 0 rows affected (0.00 sec) Slave> desc slave; +-------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+---------+-------+ | id | int(2) | YES | | NULL | | | name | char(10) | YES | | NULL | | +-------+----------+------+-----+---------+-------+ 2 rows in set (0.00 sec) Slave> insert into slave values(90,‘slave‘); # 插入一条数据 Query OK, 1 row affected (0.00 sec) Slave> select * from slave; +------+-------+ | id | name | +------+-------+ | 90 | slave | +------+-------+ 1 row in set (0.00 sec)
模拟远程连接MySQL-proxy服务器进行读写操作
[[email protected] ~]# mysql -h192.168.0.86 -uproxy -P3306 -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 12 Server version: 5.5.55-log MySQL Community Server (GPL) Copyright (c) 2000, 2017, 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> mysql> use proxy; Database changed mysql> mysql> show tables; # show 出来的只有master这个表 +-----------------+ | Tables_in_proxy | +-----------------+ | master | +-----------------+ 1 row in set (0.01 sec) mysql> desc master; +-------+----------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+----------+------+-----+---------+-------+ | id | int(2) | YES | | NULL | | | name | char(10) | YES | | NULL | | +-------+----------+------+-----+---------+-------+ 2 rows in set (0.00 sec) mysql> insert into master values(88,‘master‘); # 往master表里插入数据 Query OK, 1 row affected (0.00 sec) <<--- 写入是 OK 的 mysql> select * from master; ERROR 1146 (42S02): Table ‘proxy.master‘ doesn‘t exist # 明显查不到的，因为去找从库了，从库上没有这表。 mysql> show tables; # 我们show时只能看到 master 表，好像show只能找主库。 +-----------------+ | Tables_in_proxy | +-----------------+ | master | +-----------------+ 1 row in set (0.00 sec) mysql> select * from slave; # 我们直接查 slave 表 +------+-------+ | id | name | +------+-------+ | 90 | slave | <<--- 查到了，读操作成功 +------+-------+ 1 row in set (0.00 sec) mysql>
恢复 slave IO 线程
Slave> start slave io_thread; Query OK, 0 rows affected (0.00 sec) Slave> show slave status\G *************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: 192.168.0.88 Master_User: rep Master_Port: 3306 Connect_Retry: 60 Master_Log_File: mysql-bin.000019 Read_Master_Log_Pos: 1566 Relay_Log_File: relay-bin.000012 Relay_Log_Pos: 1468 Relay_Master_Log_File: mysql-bin.000019 Slave_IO_Running: Yes Slave_SQL_Running: Yes
再次模拟远程连接MySQL-proxy服务器查 master 表
[[email protected] ~]# mysql -h192.168.0.86 -uproxy -P3306 -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 12 Server version: 5.5.55-log MySQL Community Server (GPL) Copyright (c) 2000, 2017, 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> mysql> use proxy; Database changed mysql> mysql> select * from master; +------+--------+ | id | name | +------+--------+ | 88 | master | <<----由于从库恢复后开始复制主库数据，所以可以查到了。 +------+--------+ 1 row in set (0.00 sec)
以上MySQL-proxy读写分离完成。
存在的问题：
当模拟前端连接MySQL-proxy服务器并进行数据库操作时，MySQL-proxy服务器端屏幕有信息输出，不知道为什么？
信息如下：
[[email protected] ~]# server default db: proxy
client default db: school
syncronizing
server default db: proxy
client default db: school
syncronizing
server default db: school
client default db: proxy
syncronizing