背景:
既然有了Lvs+keepalived这样高性能的组合,那为何还要有Nginx+keepalived呢,keepalived的初衷就是为了Lvs而设计的,我们都知道Lvs是一个四层的负载均衡设备,虽然有着高性能的优势,但同时它却没有后端服务器的健康检查机制,keepalived为lvs设计了一系列的健康检查机制TCP_CHECK,UDP_CHECK,HTTP_GET等。同时lvs也可以自己写健康检查脚脚本。或者结合ldirectory来实现后端检测。但是固LVS始终无法摆脱它是一个四层设备,无法对上层协议进行解析。Nginx不一样,Nginx是一个七层的设备可以对七层协议进行解析,可以对一些请求进行过滤,还可以对请求结果进行缓存。这些都是Nginx独有的优势。但是keepalived并没有为Nginx提供健康检测。需要自己去写一些脚步来进行健康检测。关于keepalived+lvs的构建可参考我的另一篇博文:
http://ljohn.blog.51cto.com/11932290/1980547
更新:2017.11.28
笔者写了一个Ansible-role 一键部署《keppalived+nginx 高可用集群》
https://github.com/Ljohn001/Ansible-roles/tree/master/Ansible-keepalived-nginx-role
CentOS6.9,CentOS7.4 经过反复测试没毛病。正真实现一件就搞定,都准备放弃脚本投奔Ansible了。
废话不多说开始构建 keppalived+nginx 高可用集群
1、首先还是要准备环境
四台机器(CentOS7.3)
192.168.0.56 ---> proxy1 (nginx)
192.168.0.57 ---> proxy2 (nginx)
192.168.0.58 ---> web1 (httpd)
192.168.0.59 ---> web1 (httpd)
拓扑
注:
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1、这里需要保持4台机器时间同步
# ntpdate IP(ntp时钟服务器自行搭建不多介绍)
*
/5
* * * * root
/usr/sbin/ntpdate
192.168.1.99 &>
/dev/null
;hwclock -w
2、为了操作的方便后面配置对所有参与机器进行免密处理
# ssh-keygen -t rsa -P '' -f "/root/.ssh/id_rsa"
# for i in 56 57 58 59;do ssh-copy-id -i .ssh/id_rsa.pub root@192.168.0.$i;done
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2、配置realserver(web1和web2)
a、安装web程序
注意这里的realserver 可以是任何web容器(tomcat、jetty、httpd、nginx..),因为是学习,所以这里使用httpd来演示
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#yum install httpd -y
#systemctl restart httpd
# netstat -nultp| grep httpd##确保httpd启动
tcp6 0 0 :::80 :::* LISTEN 4619
/httpd
配置页面
web1:
# echo "<h1>The page from web1(58)</h1>" > /var/www/html/index.html
web2:
# echo "<h1>The page from web1(59)</h1>" > /var/www/html/index.html
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b、设置VIP及内核参数
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#编写脚本如下:
# cat setka.sh
#!/bin/bash
vip=192.168.0.100
case
$1
in
start)
echo
1 >
/proc/sys/net/ipv4/conf/all/arp_ignore
echo
1 >
/proc/sys/net/ipv4/conf/lo/arp_ignore
echo
2 >
/proc/sys/net/ipv4/conf/all/arp_announce
echo
2 >
/proc/sys/net/ipv4/conf/lo/arp_announce
ifconfig
lo:0 $vip broadcast $vip netmask 255.255.255.255 up
;;
stop)
ifconfig
lo:0 down
echo
0 >
/proc/sys/net/ipv4/conf/all/arp_ignore
echo
0 >
/proc/sys/net/ipv4/conf/lo/arp_ignore
echo
0 >
/proc/sys/net/ipv4/conf/all/arp_announce
echo
0 >
/proc/sys/net/ipv4/conf/lo/arp_announce
;;
esac
# bash setka.sh start #运行该脚本设置相关内核参数及VIP地址。
# cat /proc/sys/net/ipv4/conf/lo/arp_ignore #内核参数设置成功
1
# cat /proc/sys/net/ipv4/conf/all/arp_announce
2
# ifconfig lo:0 #VIP设置成功
lo:0 Link encap:Local Loopback
inet addr:192.168.137.10 Mask:255.255.255.255
UP LOOPBACK RUNNING MTU:65536 Metric:1
# scp setka.sh root@192.168.0.59:/root #拷贝一份给web2并执行
setka.sh 100% 547 0.5KB
/s
00:00
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3、配置nginx proxy1和2 负载均衡
a、两台proxy都安装nginx
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yum
install
-y nginx
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b、配置nginx proxy
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vim
/etc/nginx/nginx
.conf
upstream backserver {
server 192.168.0.58:80 weight=1 max_fails=3 fail_timeout=3s;
server 192.168.0.59:80 weight=2 max_fails=3 fail_timeout=3s;
}
server {
listen 80;
server_name localhost;
location / {
root html;
index index.html index.htm;
proxy_pass http:
//backserver
;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
}
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复制一份至另一台proxy(nginx)
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# scp /etc/nginx/nginx.conf root@192.168.0.57:/etc/nginx/nginx.conf
# systemctl restart nginx;ssh 192.168.0.57 ‘systemctl restart nginx’
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c、测试访问
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# for i in {1..10};do curl http://192.168.0.56;done
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
# for i in {1..10};do curl http://192.168.0.57;done
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
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#注:这里可以看出,每台proxy(nginx) 都完成了负载均衡配置,且实现了负载均衡调度。细心的同学发现后端real server 配置的权重1:2,调度大致请求调度返回也为1:2
4、配置keepalived 高可用nginx
a、每台proxy安装httpd 和keepalived
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# yum install -y httpd keepalived
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每台proxy 配置Sorry页面,这里一旦后端服务器同时无法访问,会自动调用本地的httpd服务
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# echo "<h1>Sorry,Under maintances(56).</h1>" >/var/www/html/index.html
# echo "<h1>Sorry,Under maintances(57).</h1>" >/var/www/html/index.html
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# 编辑各个proxy 的 nginx.conf,添加在upstream下添加
server 127.0.0.1:8080 backup;
或者:
# sed -i '/server 192.168.0.59:80 weight=2 max_fails=3 fail_timeout=3s;/a\server 127.0.0.1:8080 backup;' /etc/nginx/nginx.conf
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b、编辑配置文件
proxy1:
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# cat /etc/keepalived/keepalived.conf
! Configuration File
for
keepalived
global_defs {
notification_email {
root@localhost
#定义邮箱报警的邮箱地址
}
notification_email_from root@localhost
#定义发送报警信息的地址
smtp_server 127.0.0.1
#定义发送邮件的邮件服务器地址
smtp_connect_timeout 30
#定义发送邮件的超时时间
router_id ha_nginx
#全局标识
}
vrrp_script chk_nginx {
#定义检查nginx服务的脚本
script
"/etc/keepalived/chk_nginx.sh"
#脚本重启nginx,如果进程还是无法检测到,则强制停止keepalived
interval 2
#检查的间隔时间
weight -2
#检查失败的话权重减2
fall 2
#检查失败2次才认为是真正的检查失败
}
vrrp_instance VI_1 {
state MASTER
interface ens33
virtual_router_id 51
priority 100
#备用机器的keepalived的权重要小于这个权重,并且当nginx服务挂掉后100-2要小于备用机器的权重。
advert_int 1
smtp_alert
#比较重要 定义使用邮件发送,不然上面的邮件定义都是没有用的,使用了这个当状态发生改变就会发送邮件报警
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
#定义使用哪个脚本来检查。
chk_nginx
}
virtual_ipaddress {
192.168.0.100
/16
dev ens33 label ens33:1
}
}
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##拷贝配置文件至proxy2
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# scp /etc/keepalived/keepalived.conf root@192.168.0.57:/etc/keepalived/keepalived.conf
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proxy2:
修改keepalived.conf 如下两个参数:
state BACKUP
priority 99
#这里贴出我实验的配置
# cat /etc/keepalived/keepalived.conf
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! Configuration File
for
keepalived
global_defs {
notification_email {
root@localhost
#定义邮箱报警的邮箱地址
}
notification_email_from root@localhost
#定义发送报警信息的地址
smtp_server 127.0.0.1
#定义发送邮件的邮件服务器地址
smtp_connect_timeout 30
#定义发送邮件的超时时间
router_id ha_nginx
#全局标识
}
vrrp_script chk_nginx {
#定义检查nginx服务的脚本
script
"/etc/keepalived/chk_nginx.sh"
#脚本重启nginx,如果进程还是无法检测到,则强制停止keepalived
interval 2
#检查的间隔时间
weight -2
#检查失败的话权重减2
fall 2
#检查失败2次才认为是真正的检查失败
}
vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 51
priority 99
#备用机器的keepalived的权重要小于这个权重,并且当nginx服务挂掉后100-2要小于备用机器的权重。
advert_int 1
smtp_alert
#比较重要 定义使用邮件发送,不然上面的邮件定义都是没有用的,使用了这个当状态发生改变就会发送邮件报警
authentication {
auth_type PASS
auth_pass 1111
}
track_script {
#定义使用哪个脚本来检查。
chk_nginx
}
virtual_ipaddress {
192.168.0.100
/16
dev ens33 label ens33:1
}
}
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c、nginx检测脚本
#脚本先判断是否有nginx进程,然后如果没有,则会重启nginx,如果进程还是无法检测到,则强制停止keepalived,启用备用节点的作为master。
#该脚本可以有效防止HA脑裂,发现无发启动nginx尝试重启,不行再将keepalived关闭,彻底移除此节点。
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#cat /etc/keepalived/chk_nginx.sh
#!/bin/bash
N=`
ps
-C nginx --no-header|
wc
-l`
if
[ $N -
eq
0 ];
then
systemctl restart keepalived
sleep
1
if
[ `
ps
-C nginx --no-header|
wc
-l` -
eq
0 ];
then
systemctl stop keepalived
fi
fi
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d、启动keepalived及nginx
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# systemctl restart nginx;ssh 192.168.0.57 'systemctl restart nginx'
# systemctl restart keepalived.service;ssh 192.168.0.57 'systemctl restart keepalived.service'
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5、测试
1、查看地址是否在proxy1上:
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# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
00:0c:29:d6:84:65 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.56
/24
brd 192.168.0.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.0.100
/16
scope global ens33:1
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fed6:8465
/64
scope link
valid_lft forever preferred_lft forever
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测试网页是否能够打开。
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# for i in {1..5};do curl http://192.168.0.100;done
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
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这里能够正常访问,测试通过。
2、关闭主节点的keepalived测试VIP是否能够漂移至备用节点
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[root@node2 keepalived]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
00:0c:29:7c:92:ae brd ff:ff:ff:ff:ff:ff
inet 192.168.0.57
/24
brd 192.168.0.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.0.100
/16
scope global ens33:1
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe7c:92ae
/64
scope link
valid_lft forever preferred_lft forever
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查看VIP是否能正常访问
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# for i in {1..5};do curl http://192.168.0.100;done
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
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这里能够正常访问,测试通过。
5、由于我们配置的抢占模式,一旦主节点恢复,则VIP会直接漂回去。
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[root@node1 ~]
# systemctl start keepalived
[root@node1 ~]
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
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: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link
/ether
00:0c:29:d6:84:65 brd ff:ff:ff:ff:ff:ff
inet 192.168.0.56
/24
brd 192.168.0.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.0.100
/16
scope global ens33:1
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fed6:8465
/64
scope link
valid_lft forever preferred_lft forever
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测试VIP访问
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# for i in {1..5};do curl http://192.168.0.100;done
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(58)<
/h1
>
<h1>The page from web1(59)<
/h1
>
<h1>The page from web1(59)<
/h1
>
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VIP地址又被主节点抢回来,服务正常访问,通过测试
最后我们来看下一下备用节点的在主节点keepalived关闭时,系统到底做了什么
##查看日志,观察VIP漂移的整个过程
1、传递MASTER的状态
2、设置自己为MASTER状态,
3、设置VIP 虚拟地址
4、发送ARP广播地址 ,地址为:192.168.0.100 #告诉大家我现在叫MASTER,对外提供服务了。
备用节点上/var/log/messages:
Nov 13 16:46:02 localhost Keepalived_vrrp[12348]: VRRP_Instance(VI_1) Transition to MASTER STATE
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: VRRP_Instance(VI_1) Entering MASTER STATE
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: VRRP_Instance(VI_1) setting protocol VIPs.
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Sending gratuitous ARP on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Sending gratuitous ARP on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Sending gratuitous ARP on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Sending gratuitous ARP on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Sending gratuitous ARP on ens33 for 192.168.0.100
Nov 13 16:46:03 localhost Keepalived_vrrp[12348]: Remote SMTP server [127.0.0.1]:25 connected.
FAQ:
Q:再/var/log/messages日志中发现:Unable to access script `killall`
A:因为centos7精简安装,没有killall命令,需要安装一下
# yum install psmisc -y
至此在CentOS7.3上完成了:keepalived 高可用nginx,有兴趣的同学可以玩一下,有什么问题,还请批评指正。