Nginx+keepalived高可用（双主模式）
负载均衡技术对于一个网站尤其是大型网站的web服务器集群来说是至关重要的！做好负载均衡架构，可以实现故障转移和高可用环境，避免单点故障，保证网站健康持续运行。由于业务扩展，网站的访问量不断加大，负载越来越高。现需要在web前端放置nginx负载均衡,同时结合keepalived对前端nginx实现HA高可用。
介绍下Nginx和keepalive
1.Nginx
Nginx 是一个很强大的高性能Web和反向代理服务器，它具有很多非常优越的特性：
Nginx作为负载均衡服务器：Nginx 既可以在内部直接支持 Rails 和 PHP 程序对外进行服务，也可以支持作为 HTTP代理服务器对外进行服务。Nginx采用C进行编写，不论是系统资源开销还是CPU使用效率都比 Perlbal 要好很多。
2.keepalive
Keepalived是Linux下面实现VRRP备份路由的高可靠性运行件。基于Keepalived设计的服务模式能够真正做到主服务器和备份服务器故障时IP瞬间无缝交接。二者结合，可以构架出比较稳定的软件LB方案。
Nginx+keepalive高可用方式有两种：
1.Nginx+keepalived 主从配置
这种方案，使用一个vip地址，前端使用2台机器，一台做主，一台做备，但同时只有一台机器工作，另一台备份机器在主机器不出现故障的时候，永远处于浪费状态，对于服务器不多的网站，该方案不经济实惠。
2.Nginx+keepalived 双主配置
这种方案，使用两个vip地址，前端使用2台机器，互为主备，同时有两台机器工作，当其中一台机器出现故障，两台机器的请求转移到一台机器负担，非常适合于当前架构环境。所以在这里就详细介绍下双主模型配置
一、拓扑结构
二、测试环境介绍
系统centos7.4 64位
centos6.9 64位
前端node1服务器：DIP:192.168.92.136
VIP1:192.168.92.23
VIP2：192.168.92.24
前端node2服务器：DIP:192.168.92.133
VIP1:192.168.92.24
VIP2：192.168.92.23
后端服务器：web node3:192.168.92.123
web node4:192.168.92.124
web node5:192.168.92.125
我们开始之前先把防火墙和selinux关掉，很多时候我们服务器之间不通都是这些原因造成的。
三、软件安装
Nginx和keepalive的安装非常简单，我们可以直接使用yun来安装。
yum install keepalived nginx -y
后端服务器我们同样用yum来装上Nginx
后端node3
# yum -y install nginx
# echo "this is 192.168.92.123" > /usr/share/nginx/html/index.html
# service nginx start
# curl 192.168.92.123
this is 192.168.92.123
后端node4
# yum -y install nginx
# echo "this is 192.168.92.124" > /usr/share/nginx/html/index.html
# service nginx start
# curl 192.168.92.124
this is 192.168.92.124
后端node5
# yum -y install nginx
# echo "this is 192.168.92.125" > /usr/share/nginx/html/index.html
# service nginx start
# curl 192.168.92.125
this is 192.168.92.125
四、在node1、node2上配置Nginx
# vim /etc/nginx/conf.d/node2.conf #在扩展配置目录中配置需要注释掉主配置文件中的server部分
upstream web1 {
#ip_hash; #hash绑定ip
server 192.168.92.123:80;
server 192.168.92.124:80;
server 192.168.92.125:80;
}
server {
listen 80;
server_namewww.node.com;
index index.html index.htm;
location / {
proxy_set_header Host $host;
proxy_set_header X-Forwarded-For $remote_addr;
proxy_pass http://web1;
}
}
五、在node1上配置keepalive
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id node1
vrrp_mcast_gruop4 224.0.100.23
}
vrrp_script chk_haproxy {
script "/etc/keepalived/chk_nginx.sh"
interval 2
weight 2
}
vrrp_instance VI_1 {
state MASTER
interface ens37
virtual_router_id 51
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 111123
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.92.23
}
}
vrrp_instance VI_2 {
state BACKUP
interface ens37
virtual_router_id 151
priority 98
advert_int 1
authentication {
auth_type PASS
auth_pass 123123
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.92.24
}
}
六、在node2上配置keepalive
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
root@localhost
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id node1
vrrp_mcast_gruop4 224.0.100.23
}
vrrp_script chk_haproxy {
script "/etc/keepalived/chk_nginx.sh"
interval 2
weight 2
}
vrrp_instance VI_1 {
state BACKUP
interface ens34
virtual_router_id 51
priority 98
advert_int 1
authentication {
auth_type PASS
auth_pass 111123
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.92.23
}
}
vrrp_instance VI_2 {
state MASTER
interface ens34
virtual_router_id 151
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 123123
}
track_script {
chk_nginx
}
virtual_ipaddress {
192.168.92.24
}
}
七、在双主服务器上添加检测脚本
此脚本作用是检测Nginx是否运行，如果没有运行就启动Nginx
如果启动失败则停止keepalive，保证备用服务器正常运行。
# cat /etc/keepalived/chk_nginx.sh
#!/bin/bash
status=$(ps -C nginx --no-heading|wc -l)
if [ "${status}" = "0" ]; then
systemctl start nginx
status2=$(ps -C nginx --no-heading|wc -l)
if [ "${status2}" = "0"]; then
systemctl stop keepalived
fi
fi
八、启动Nginx、keepalive服务
# service nginx start
# service keepalived start
# service nginx start
# service keepalived start
九、查看VIP并测试访问
# ip a
..........
ens34:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:ca:0b:2b brd ff:ff:ff:ff:ff:ff
inet 192.168.92.133/24 brd 192.168.92.255 scope global dynamic ens34
valid_lft 1293sec preferred_lft 1293sec
inet 192.168.92.24/32 scope global ens34
valid_lft forever preferred_lft forever
inet6 fe80::9bff:2e2b:aebb:e35/64 scope link
valid_lft forever preferred_lft forever
.........
# ip a
..........
ens37:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:04:b6:17 brd ff:ff:ff:ff:ff:ff
inet 192.168.92.136/24 brd 192.168.92.255 scope global dynamic ens37
valid_lft 1567sec preferred_lft 1567sec
inet 192.168.92.23/32 scope global ens37
valid_lft forever preferred_lft forever
inet6 fe80::7ff4:9608:5903:1a4b/64 scope link
valid_lft forever preferred_lft forever
..........
# curl http://192.168.92.23
this is 192.168.92.123
# curl http://192.168.92.23
this is 192.168.92.124
# curl http://192.168.92.23
this is 192.168.92.125
# curl http://192.168.92.24
this is 192.168.92.124
十、测试脚本是否能正常运行
手动停止Nginx后自动恢复启动
# systemctl stop nginx
# ss -tnlp
State Recv-Q Send-Q Local Address:Port Peer Address:Port
LISTEN 0 128 *:80 *:* users:(("nginx",pid=20257,fd=6),("nginx",pid=20256,fd=6))
LISTEN 0 128 *:22 *:* users:(("sshd",pid=913,fd=3))
LISTEN 0 100 127.0.0.1:25 *:* users:(("master",pid=991,fd=13))
LISTEN 0 128 :::22 :::* users:(("sshd",pid=913,fd=4))
LISTEN 0 100 ::1:25 :::* users:(("master",pid=991,fd=14))
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