基于Lvs-nat模型的discuz负载均衡实现
前言：
lvs-nat模型需要一台机器作为前端VS(Virtual Server)主机，和两台作为后端的RS(Real Server)才能够实现负载均衡效果
因为需要负载均衡应用Discuz，同一客户端请求如果被调度到不同的RS上，无法保障用户访问会话持久不丢失，和数据的一致性，所以还需要考虑会话保持和数据共享的问题。
会话保持的解决方案有三种：源地址哈希、会话集群、会话服务器，这里选择源地址；即将来自同一客户端的请求调度至同一台服务器，只需要将lvs集群的调度算法配置为SH(Source Hash)即可，比较简单，但实际上这种方案存在弊端，如果初始调度的RS宕机，将请求调度至其他RS时，就无法获取到之前的会话了，此处我们暂时不考虑这一情况！随后我会提供相关博客。
数据共享的解决方案在前面一篇文章（rsync+inotify）中提到过，此处我们选择NFS，由于其搭建起来比较方便，性能还不错。
环境需求：
HostVS
OS:CentOS-7-x86_64
hostname:ws1
eno16777736:10.0.0.61/8(VIP)
eno33554984:172.18.64.1/16(DIP)
gateway:10.0.0.254
HostRS1
OS:CentOS-7-x86_64
hostname:ws2
eno16777736:172.18.64.2/16 (RIP1)
gateway:172.18.64.254
HostRS2
OS:CentOS-7-x86_64
hostname:ws3
eno16777736:172.18.64.3/16 (RIP2)
gateway:172.18.64.254
HostDB
OS:CentOS-7-x86_64
hostname:ws4
eno16777736:172.18.64.4/16
gateway:172.18.64.254
时间同步：
# ntpdate cn.pool.ntp.org # hwclock --sysohc
安装软件：
HostDB
安装二进制mariadb-5.5.46
详细配置请入传送门：http://wscto.blog.51cto.com/11249394/1783131
安装NFS
# yum install -y nfs-utils
HostRS2
安装nginx，注意nginx属于epel源
# yum install-y nginx php-fpm php-mbstring php-mysql nfs-utils mariadb
HostRS1
安装nginx，注意nginx属于epel源
# yum install-y nginx php-fpm php-mbstring php-mysql nfs-utils mariadb
HostVS
安装LVS的cli接口程序ipvsadm
# yum install -y ipvsadm
配置集群
HostDB
配置mariadb
安全初始化完成后，创建discuz数据库和discuz用户，并授权其可远程操作数据库
# mysql_secure_installation # mysql -u root -p > create database discuz; > create user 'discuz'@'lodalhost' identified by '123456'; > grant all privileges on discuz.* to 'discuz'@'%' identified by '123456'; > flush privileges;
配置NFS
# mkdir /nfshare/ # ls -ld /nfshare/ drwxr-xr-x 2 root root 6 May 9 17:01 /nfshare/ # echo "/nfshare/ 10.0.0.62(rw,no_root_squash,async) 10.0.0.63(rw,no_root_squash,async)" > /etc/exports # systemctl start rpcbind Starting rpcbind: [ OK ] # systemctl start nfs-server Starting NFS services: [ OK ] Starting NFS quotas: [ OK ] Starting NFS mountd: [ OK ] Starting NFS daemon: [ OK ] Starting RPC idmapd: [ OK ] # systemctl enable rpcbind # systemctl enable nfs-server # chkconfig rpcbind --list rpcbind 0:off 1:off 2:on 3:on 4:on 5:on 6:off # chkconfig nfs --list nfs 0:off 1:off 2:on 3:on 4:on 5:on 6:off # showmount -e 127.0.0.1 Export list for 127.0.0.1: /nfshare/ 10.0.0.62,10.0.0.63
注意：rpcbind和nfs两个服务启动顺序不能更换，否则会出问题
解压discuz的程序包至/nfsshare/目录
# mkdir /nfshare/discuz # unzip /Discuz_X3.2_SC_UTF8.zip -d /nfshare/discuz/ # ls /nfshare/discuz/ readme upload utility
HostR2
测试链接HostDB上的mariadb
# mysql -h 172.18.64.4 -u discuz -p
挂载HostDB上的NFS共享存储目录，属主属组修改为apache
# showmount -e 172.18.64.4 Export list for 172.18.64.4: /nfshare/ 10.0.0.62,10.0.0.63 # mkdir /htdocs # ls -ld /htdocs/ drwxr-xr-x 2 root root 6 May 9 17:05 /htdocs/ # mount -t nfs 172.18.64.4:/nfshare /htdocs # ls /htdocs/ discuz # chown -R apache:apache /htdocs/discuz/
启动php-fpm
# systemctl start php-fpm.service # ss -tnl | grep 9000
配置nginx的配置文件
# vim /etc/nginx/nginx.conf
server {
listen 80;
server_name ws3
# Load configuration files for the default server block.
include /etc/nginx/default.d/*.conf;
location / {
root /htdocs/discuz/upload;
index index.html index.htm index.php;
}
location ~ \.php$ {
root /htdocs/discuz/upload;
fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
include /etc/nginx/fastcgi.conf;
}
error_page 404 /404.html;
location = /40x.html {
}
error_page 500 502 503 504 /50x.html;
location = /50x.html {
}
}
# nginx -t
nginx: the configuration file /etc/nginx/nginx.conf syntax is ok
nginx: configuration file /etc/nginx/nginx.conf test is successful
# nginx
# ss -tnl | grep 80
LISTEN 0 128 *:80 *:*
测试访问discuz安装页面主机加上最后的/
# curl -I http://172.18.64.3/install/ HTTP/1.1 200 OK Server: nginx/1.6.3 Date: Mon, 09 May 2016 10:23:50 GMT Content-Type: text/html Connection: keep-alive X-Powered-By: PHP/5.4.16
HostRS1
配置同上
HostVS
打开核心转发功能
# echo 1 > /proc/sys/net/ipv4/ip_forward
先使用rr调度算法，期望会话丢失情况出现，若出现会话丢失情况，改用sh(源地址哈希)调度算法再测试，期望会话能保持
# ipvsadm -A -t 10.0.0.61:80 -s rr # ipvsadm -a -t 10.0.0.61:80 -r 172.18.64.2:80 -m # ipvsadm -a -t 10.0.0.61:80 -r 172.18.64.3:80 -m
测试：
浏览器访问http://10.0.0.61/install/