双机热备是指两台机器都在运行,但并非两台机器同时在提供服务。 当提供服务的一台出现故障的时候,另外一台会马上自动接管并且提供服务,且切换的时间非常短。
keepalived的工作原理是VRRP——虚拟路由冗余协议。
测试环境如下:
ip
vip
master
192.168.174.135
192.168.174.140
backup
192.168.174.137
192.168.174.140
回到顶部 nginx 安装
sudo apt-get install nginx 查找配置文件位置
sudo find / -name nginx.conf /etc/nginx/nginx.conf 修改配置文件(nginx.conf)
复制代码 user www-data; worker_processes 4; pid /run/nginx.pid;
events { worker_connections 1024; }
http { sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048;
include /etc/nginx/mime.types;
default_type application/octet-stream;
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
server {
listen 80 default_server;
server_name test;
charset utf-8;
location / {
root html;
index index.html index.htm;
proxy_set_header X-Real_IP $remote_addr;
client_max_body_size 100m;
}
}
} 复制代码 文件/usr/share/nginx/html/index.html
在192.168.174.135上加上 Welcome to nginx! 135
在192.168.174.137上加上 Welcome to nginx! 137
启动
sudo service nginx start
关闭
sudo service nginx stop 回到顶部 keepalived 安装
下载keepalived-1.2.19.tar.gz
tar –zxvf keepalived-1.2.19.tar.gz cd keepalived-1.2.19 ./configure --prefix=/usr/local/keepalived make sudo make install 期间可能出现问题:
!!! OpenSSL is not properly installed on your system. !!! !!! Can not include OpenSSL headers files. !!!
解决
sudo apt-get install libssl.dev 建立软链接
sudo ln -s /usr/local/keepalived/sbin/keepalived /sbin/ sudo ln -s /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/ sudo ln -s /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/ 启动
sudo keepalived -D -f /usr/local/keepalived/etc/keepalived/keepalived.conf 关闭
sudo killall keepalived 配置(keepalived.conf):
复制代码 global_defs { router_id NODEA }
vrrp_instance VI_1 {
state MASTER
interface eth0 #监测网络接口
virtual_router_id 50 #主、备必须一样
priority 100 #优先级:主>备
advert_int 1
authentication {
auth_type PASS #VRRP认证,主备一致
auth_pass 1111 #密码
}
virtual_ipaddress { 192.168.174.140/24 #VRRP HA虚拟地址 } } 复制代码 备用节点的配置
复制代码 global_defs { router_id NODEB }
vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 50 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 }
virtual_ipaddress { 192.168.174.140/24 } } 复制代码 回到顶部 测试 双击热备
两台机子均启动nginx和keepalived,浏览器各自访问
浏览器访问:http://192.168.174.140/,显示的是MASTER的页面。
同样用ip appr可以验证:
135机器:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 00:0c:29:39:d4:88 brd ff:ff:ff:ff:ff:ff
inet 192.168.174.135/24 brd 192.168.174.255 scope global eth0
valid_lft forever preferred_lft forever
inet 192.168.174.140/24 scope global secondary eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe39:d488/64 scope link
valid_lft forever preferred_lft forever
137机器:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
link/ether 00:0c:29:cf:23:62 brd ff:ff:ff:ff:ff:ff
inet 192.168.174.137/24 brd 192.168.174.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fecf:2362/64 scope link
valid_lft forever preferred_lft forever
现在关闭135机器的keepalived。
但当nginx宕掉或整个机子宕机后,这种情况不行了——通过浏览器访问192.168.174.140访问不到资源。
nginx宕掉/机器宕掉热备
为了解决上一问题,可以利用脚本,当检测到nginx进程宕掉后,自动关闭keepalived进程,从而实现热备份。
主节点的配置
复制代码 global_defs { router_id NODEA }
vrrp_script chk_http_port { script "/home/jimite/keepalived/chk_nginx_pid.sh" interval 2 weight 2 }
vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 50 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } track_script { chk_http_port } virtual_ipaddress { 192.168.174.140/24 } } 复制代码 备用节点的配置
复制代码 global_defs { router_id NODEB }
vrrp_script chk_http_port { script "/home/jihite/keepalived/chk_nginx_pid.sh" interval 2 weight 2 }
vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 50 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } track_script { chk_http_port }
virtual_ipaddress {
192.168.174.140/24
}
} 复制代码 其中/home/jimite/keepalived/chk_nginx_pid.sh为
复制代码
#!/bin/bash
A=ps -C nginx --no-header |wc -l
if [ $A -eq 0 ]
then
echo 'nginx server is died'
sudo killall keepalived
fi
问题:杀死keepalived进程后,可以实现vip的偏移,但是原机器的vip无法自动删除
原因:VRRP协议原理是:只有MASTER对外发送消息。各BACKUP接受消息,当接受不到消息时会在剩下的BACKUP机器中选出新的MASTER。
之前用kill -9 pid 或killall pid杀死keepalived进程,导致安装keepalived不能发送信息,BACKUP收不到信息升级为MASTER,但是由于进程被杀死【非正常关闭】,导致keepalived没有能力自己删除vip。
解决方案:关闭keepalived时用命令
service keepalived stop 或 kill -15 pid(注:只删除第一个进程号)
存在问题:
非正常关闭keepalived。 禁止使用kill -9 或killall杀死keepalived。