Linux运维之mysql数据库的读写分离

Linux运维之mysql数据库的读写分离

什么是读写分离及什么是mysql-proxy

• 读写分离，基本的原理是让主数据库处理事务性增、改、删操作（INSERT;UPDATE、DELETE），而从数据库处理SELECT查询操作。数据库复制被用来把事务性操作导致的变更同步到集群中的从数据库。
• 数据库的“写”操作是比较耗时的。
• 但是数据库的“读”（从oracle读10000条数据可能只要5秒钟）。
• 所以读写分离，解决的是，数据库的写入，影响了查询的效率。
• 数据库不一定要读写分离，如果程序使用数据库较多时，而更新少，查询多的情况下会考虑使用，利用数据库 主从同步 。可以减少数据库压力，提高性能。当然，数据库也有其它优化方案。memcache 或是 表折分，或是搜索引擎。都是解决方法。
• MySQL Proxy最强大的一项功能是实现“读写分离(Read/Write Splitting)”。基本的原理是让主数据库处理事务性查询，而从数据库处理SELECT查询。数据库复制被用来把事务性查询导致的变更同步到集群中的从数据库。 当然，主服务器也可以提供查询服务。使用读写分离最大的作用无非是环境服务器压力。

配置步骤

实验环境准备：
用server3来做proxy，1和2一个读一个写
做以下实验之前，先做好server1和server2的gtid主从复制

#server3上：

tar zxf mysql-proxy-0.8.5-linux-el6-x86-64bit.tar.gz -C /usr/local
cd /usr/local/
ln -s mysql-proxy-0.8.5-linux-el6-x86-64bit/ mysql-proxy	#软链接便于访问

cd /usr/local/mysql-proxy/bin
./mysql-proxy --help	##查看帮助
./mysql-proxy --help-proxy	##查看proxy的帮助
./mysql-proxy --help-all	##查看所有帮助

cd /usr/local/mysql-proxy
mkdir conf	##建立配置文件目录

#编辑配置文件（自己手动新建）

vim mysql-proxy.conf	

[mysql-proxy]
proxy-address=0.0.0.0:3306
proxy-backend-addresses=172.25.136.1:3306
proxy-read-only-backend-addresses=172.25.136.2:3306
proxy-lua-script=/usr/local/mysql-proxy/share/doc/mysql-proxy/rw-splitting.lua
pid-file=/usr/local/mysql-proxy/log/mysql-proxy.pid
plugins=proxy
log-file=/usr/local/mysql-proxy/log/mysql-proxy.log
log-level=debug
keepalive=true
daemon=true

#创建日志目录

mkdir /usr/local/mysql-proxy/log

#修改lua脚本

min_idle_connections = 1,	##把原来的4和8改为1和2，默认超过4个连接才会启动读写分离，改为1个好测试
max_idle_connections = 2,

#启动mysql-proxy

/usr/local/mysql-proxy/bin/mysql-proxy --defaults-file=/usr/local/mysql-proxy/conf/mysql-proxy.conf

启动报错：

	2019-03-15 14:15:04: (critical) mysql-proxy-cli.c:326: loading config from '/usr/local/mysql-proxy/conf/mysql-proxy.conf' failed: permissions of /usr/local/mysql-proxy/conf/mysql-proxy.conf aren't secure (0660 or stricter required)
2019-03-15 14:15:04: (message) Initiating shutdown, requested from mysql-proxy-cli.c:328
2019-03-15 14:15:04: (message) shutting down normally, exit code is: 1

#因为配置文件权限过大

chmod 660 /usr/local/mysql-proxy/conf/mysql-proxy.conf=

再启动，正常

#查看日志

cat /usr/local/mysql-proxy/log/mysql-proxy.log
看到两个节点都加进来了

2019-03-15 15:07:22: (message) chassis-unix-daemon.c:136: [angel] we try to keep PID=2521 alive
2019-03-15 15:07:22: (debug) chassis-unix-daemon.c:157: waiting for 2521
2019-03-15 15:07:22: (debug) chassis-unix-daemon.c:121: we are the child: 2521
2019-03-15 15:07:22: (critical) plugin proxy 0.8.5 started
2019-03-15 15:07:22: (debug) max open file-descriptors = 1024
2019-03-15 15:07:22: (message) proxy listening on port 0.0.0.0:3306
2019-03-15 15:07:22: (message) added read/write backend: 172.25.136.1:3306
2019-03-15 15:07:22: (message) added read-only backend: 172.25.136.2:3306

#在server1上授权新用户读写权限

mysql> grant insert,update,select on *.* to wsp@'%' identified by 'Wsp+123ld';

mysql> flush privileges;

mysql> use westos;
Database changed
mysql> create table usertb (
    -> username varchar(10) not null,
    -> password varchar(15) not null);

mysql> desc usertb;

#在物理机上打开一个shell来连接数据库

[kiosk@foundation0 ~]$ mysql -h 172.25.136.3 -uwsp -pWsp+123ld

#然后在server3上看到连接已经建立

[root@server3 log]# lsof -i:3306
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mysql-pro 2521 root   10u  IPv4  28318      0t0  TCP *:mysql (LISTEN)
mysql-pro 2521 root   11u  IPv4  28362      0t0  TCP server3:mysql->foundation0.ilt.example.com:55716 (ESTABLISHED)
mysql-pro 2521 root   12u  IPv4  28363      0t0  TCP server3:47376->server1:mysql (ESTABLISHED)

#在物理机上再打开一个shell来连接数据库
#再到server3上查看

[root@server3 log]# lsof -i:3306
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mysql-pro 2521 root   10u  IPv4  28318      0t0  TCP *:mysql (LISTEN)
mysql-pro 2521 root   11u  IPv4  28362      0t0  TCP server3:mysql->foundation0.ilt.example.com:55716 (ESTABLISHED)
mysql-pro 2521 root   12u  IPv4  28363      0t0  TCP server3:47376->server1:mysql (ESTABLISHED)
mysql-pro 2521 root   13u  IPv4  28709      0t0  TCP server3:mysql->foundation0.ilt.example.com:55722 (ESTABLISHED)
mysql-pro 2521 root   14u  IPv4  28710      0t0  TCP server3:47382->server1:mysql (ESTABLISHED)

‘发现两次连接都指向server1’

#在物理机上再打开一个shell来连接数据库
#再到server3上查看

[root@server3 log]# lsof -i:3306
COMMAND    PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mysql-pro 2521 root   10u  IPv4  28318      0t0  TCP *:mysql (LISTEN)
mysql-pro 2521 root   11u  IPv4  28362      0t0  TCP server3:mysql->foundation0.ilt.example.com:55716 (ESTABLISHED)
mysql-pro 2521 root   12u  IPv4  28363      0t0  TCP server3:47376->server1:mysql (ESTABLISHED)
mysql-pro 2521 root   13u  IPv4  28709      0t0  TCP server3:mysql->foundation0.ilt.example.com:55722 (ESTABLISHED)
mysql-pro 2521 root   14u  IPv4  28710      0t0  TCP server3:47382->server1:mysql (ESTABLISHED)
mysql-pro 2521 root   15u  IPv4  28769      0t0  TCP server3:mysql->foundation0.ilt.example.com:55726 (ESTABLISHED)
mysql-pro 2521 root   16u  IPv4  28770      0t0  TCP server3:55914->server2:mysql (ESTABLISHED)

‘这次连接到了server2，说明读写分离启用’

#测试读写分离
在物理机上插入数据：

MySQL [(none)]> use westos
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
MySQL [westos]> insert into usertb values('user1','123');
MySQL [westos]> select * from usertb;
+----------+----------+
| username | password |
+----------+----------+
| user1    | 123      |
+----------+----------+
1 row in set (0.00 sec)

发现server1和server2都能看到，看不出读写分离，因为存在主从复制

现在到server2上关闭复制

mysql> stop slave;

这时再在物理机上插入数据
MySQL [westos]> insert into usertb values ('user4','123');
Query OK, 1 row affected (0.01 sec)

MySQL [westos]> select * from usertb;
+----------+----------+
| username | password |
+----------+----------+
| user1    | 123      |
| user2    | 123      |
+----------+----------+
2 rows in set (0.00 sec)

发现插入的数据看不到，但是在server1上可以看到，这就说明了它在读的时候读的是server2上的数据，而写操作却写在了server1上