集群介绍，keepalived介绍，用keepalived配置高可用集群
集群介绍[*]根据功能划分为两大类：高可用和负载均衡
[*]高可用集群通常为两台服务器，一台工作，另外一台作为冗余，当提供服务的机器宕机，冗余将接替继续提供服务
[*]业内有个综合评分比如4个九，甚至5个九六个九来衡量服务的高可用，一般大企业的核心业务都有高可用，如果一个机器故障，一分钟之内就可以切换到另一台上
[*]实现高可用的开源软件有：heartbeat、keepalived
[*]负载均衡集群，需要有一台服务器作为分发器，它负责把用户的请求分发给后端的服务器处理，在这个集群里，除了分发器外，就是给用户提供服务的服务器了，这些服务器数量至少为2
[*]实现负载均衡的开源软件有LVS、keepalived、haproxy、nginx，商业的有F5、Netscaler
keepalived介绍
[*]在这里我们使用keepalived来实现高可用集群，因为heartbeat在centos6上有一些问题，影响实验效果，并更新不及时
[*]keepalived通过VRRP（Virtual Router Redundancy Protocl即虚拟路由冗余协议）来实现高可用。
[*]在这个协议里会将多台功能相同的路由器（其实是一台机器）组成一个小组，这个小组里会有1个master角色和N（N>=1）个backup角色。
[*]master会通过组播的形式向各个backup发送VRRP协议的数据包，当backup收不到master发来的VRRP数据包时，就会认为master宕机了。此时就需要根据各个backup的优先级来决定谁成为新的mater。
[*]Keepalived要有三个模块，分别是core、check和vrrp。其中core模块为keepalived的核心，负责主进程的启动、维护以及全局配置文件的加载和解析，check模块负责健康检查，vrrp模块是来实现VRRP协议的。
用keepalived配置高可用集群
[*]准备两台机器130和132，130作为master，132作为backup
[*]两台机器都执行yum install -y keepalived
[*]两台机器都安装nginx，其中130上已经编译安装过nginx，132上需要yum安装nginx: yum install -y nginx
[*]之所以选择nginx，在生产环境中，好多企业把它作为负载均衡器，如果它挂掉，影响后面好多web服务器，所以不能出现单点故障
[*]编辑130上的keepalived配置文件，
# > /etc/keepalived/keepalived.conf
# vim !$
vim /etc/keepalived/keepalived.conf
global_defs { #这个全局定义参数
notification_email { #出现问题给邮箱发邮件，
aming@aminglinux.com
}
notification_email_from root@aminglinux.com #由哪一个邮件发送
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_nginx { #检测一个服务是否正常，需要有个脚本
script "/usr/local/sbin/check_ng.sh"
interval 3 # 3秒检测一次
}
vrrp_instance VI_1 { # 定义master相关的
state MASTER #如果是从就是backup
interface ens33 #定义网卡
virtual_router_id 51# 定义路由器的id
priority 100 #定义权重
advert_int 1
authentication { #认证相关
auth_type PASS
auth_pass aminglinux>com
}
virtual_ipaddress { #定义vip（公有的ip）
192.168.21.100
}
track_script { #加载服务
chk_nginx
}
}
[*]在130上编辑监控脚本
# vim /usr/local/sbin/check_ng.sh
#!/bin/bash
#时间变量，用于记录日志
d=`date --date today +%Y%m%d_%H:%M:%S`
#计算nginx进程数量
n=`ps -C nginx --no-heading|wc -l`
#如果进程为0，则启动nginx，并且再次检测nginx进程数量，
#如果还为0，说明nginx无法启动，此时需要关闭keepalived(防止脑裂)
if [ $n -eq "0" ]; then
/etc/init.d/nginx start
n2=`ps -C nginx --no-heading|wc -l`
if [ $n2 -eq "0"]; then
echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log
systemctl stop keepalived
fi
fi
[*]给脚本755权限，并启动keepalived服务
# chmod 755 /usr/local/sbin/check_ng.sh
# systemctl start keepalived
# ps aux |grep keepa
root 28950.00.0 1186081388 ? Ss 23:20 0:00 /usr/sbin/keepalived -D
root 28960.10.1 1274683304 ? S 23:20 0:00 /usr/sbin/keepalived -D
root 28990.30.1 1274082836 ? S 23:20 0:00 /usr/sbin/keepalived -D
root 29610.00.0 112676 980 pts/1 S+ 23:20 0:00 grep --color=auto keepa
[*]检测下nginx可以自动加载不
# ps aux |grep nginx
root 10160.00.0460081260 ? Ss 20:52 0:00 nginx: master process /usr/localnginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
nobody 10170.00.2484964152 ? S 20:52 0:00 nginx: worker process
nobody 10180.00.2484963896 ? S 20:52 0:00 nginx: worker process
root 29820.00.0 112680 980 pts/1 S+ 23:20 0:00 grep --color=auto nginx
# /etc/init.d/nginx stop
Stopping nginx (via systemctl): [确定]
# ps aux |grep nginx
root 32661.00.0460081252 ? Ss 23:22 0:00 nginx: master process /usr/localnginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
nobody 32670.00.2484963892 ? S 23:22 0:00 nginx: worker process
nobody 32680.00.2484963892 ? S 23:22 0:00 nginx: worker process
root 32730.00.0 112676 984 pts/1 S+ 23:22 0:00 grep --color=auto nginx
[*]日志
# less /var/log/messages
[*]查看vip
# ip add
1: lo: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:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:87:fb:87 brd ff:ff:ff:ff:ff:ff
inet 192.168.21.128/24 brd 192.168.21.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.21.100/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::68fd:e6fa:c781:f5a6/64 scope link
valid_lft forever preferred_lft forever
3: ens37:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:87:fb:91 brd ff:ff:ff:ff:ff:ff
inet 192.168.110.136/24 brd 192.168.110.255 scope global dynamic ens37
valid_lft 1278sec preferred_lft 1278sec
inet6 fe80::c559:4a92:72f1:b448/64 scope link
valid_lft forever preferred_lft forever
[*] 132上编辑配置文件
# > /etc/keepalived/keepalived.conf
# vim /etc/keepalived/keepalived.conf
global_defs {
notification_email {
aming@aminglinux.com
}
notification_email_from root@aminglinux.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_nginx {
script "/usr/local/sbin/check_ng.sh"
interval 3
}
vrrp_instance VI_1 {
state BACKUP
interface ens33
virtual_router_id 51
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass aminglinux>com
}
virtual_ipaddress {
192.168.21.100
}
track_script {
chk_nginx
}
}
[*]132上编辑监控脚本
# vim /usr/local/sbin/check_ng.sh
#时间变量，用于记录日志
d=`date --date today +%Y%m%d_%H:%M:%S`
#计算nginx进程数量
n=`ps -C nginx --no-heading|wc -l`
#如果进程为0，则启动nginx，并且再次检测nginx进程数量，
#如果还为0，说明nginx无法启动，此时需要关闭keepalived
if [ $n -eq "0" ]; then
systemctl start nginx
n2=`ps -C nginx --no-heading|wc -l`
if [ $n2 -eq "0"]; then
echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log
systemctl stop keepalived
fi
fi
[*]给脚本755权限并启动keepalived
# chmod 755 /usr/local/sbin/check_ng.sh
# systemctl start keepalived
测试
[*]curl或者浏览器打开
# curl localhost@192.168.21.128
master,master.
# curllocalhost@192.168.21.129
backup,backup.
# curllocalhost@192.168.21.100
master,master.
[*]测试高可用
# systemctl stop keepalived
# curl localhost@192.168.21.100
backup,backup.
# systemctl startkeepalived
# curl localhost@192.168.21.100
master,master.
扩展
[*]heartbeat和keepalived比较
[*]DRBD工作原理和配置
[*]mysql+keepalived
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