搭建高可用集群 --- keepalived的介绍及简单配置

本文索引：

集群介绍

keepalived介绍

keepalived配置高可用集群

集群介绍

根据功能划分为2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。按可用的效率衡量高可用，例如“4个9”即99.99%的可用性，在99.99%的时间上不允许服务器宕机，当服务器宕机后作为冗余的服务器将立即接替主服务器提供服务，切换的时间间隔也较短，给用户造成的影响较小。实现高可用的开源软件有：heartbeat、keepalived。

负载均衡集群：通常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集群进行处理，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，并且这些服务器的数量至少为2台。实现负载均衡的开源软件有LVS、keepalived、haproxy、nginx，商业的负载均衡器有F5、Netscaler，优点为高并发量、高稳定性。

keepalived介绍

keepalived通过VRRP(Virtual Router Redundancy Protocol，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组成一个小组，这个小组里会有1个master角色和N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已宕机。此时就需要根据各个backup的优先级来决定哪个backup成为新的master。

keepalived有三个模块，分别是core、check和vrrp。其中core模块是keepalived的核心，负责主进程的启动、维护及全局配置文件的加载和解析；check模块负责健康检查；vrrp模块用来实现VRRP协议。

keepalived配置

test1:192.168.65.133 test2:192.168.65.134
test1作为master，test2作为backup

test1/test2都安装keepalived和nginx

# 如果主机内已经源码安装过nginx就不需要再安装了
[root@test1 ~]# yum install -y keepalived
[root@test1 ~]# yum install -y nginx

[root@test2 ~]# yum install -y keepalived
[root@test2 ~]# yum install -y nginx

更改配置文件

# 默认安装keepalived后会有一个keepalived.conf,这里清空内容后输入下列的代码
[root@test1 ~]# > /etc/keepalived/keepalived.conf
[root@test1 ~]# vim /etc/keepalived/keepalived.conf
# 全局定义参数
global_defs {
# 出现问题时发邮件，邮件地址自定义
notification_email {
1245626656@qq.com
}
notification_email_from 1245626656@qq.com
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}

# 用来检测服务是否正常
vrrp_script chk_nginx {
# 自定义脚本：检测服务是否正常
script "/usr/local/sbin/check_ng.sh"
# 检测间隔3s
interval 3
}

# 定义相关master信息
vrrp_instance VI_1 {
# 角色定义：主为MASTER，从为BACKUP
state MASTER
# 定义发送数据包的网卡
interface ens33
# 定义路由器id
virtual_router_id 51
# 权重
priority 100
advert_int 1
# 定义认证信息
authentication {
auth_type PASS
auth_pass test1
}
# 定义公有ip，正常时master绑定，master宕机后backup绑定
virtual_ipaddress {
192.168.188.100
}
# 加载检测脚本，对于上面
track_script {
chk_nginx
}
}

编辑检测脚本

# 检测服务是否正常，脚本所在路径在/etc/keepalived/keepalived.conf内定义
[root@test1 ~]# 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
if [ $n -eq "0" ]; then
/etc/init.d/nginx start
n2=`ps -C nginx --no-heading|wc -l`
# 执行启动nginx后发现nginx启动不成功，就关闭keepalived服务，并记录日志
if [ $n2 -eq "0"  ]; then
echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log
systemctl stop keepalived
fi
fi

[root@test1 ~]# chmod 755 /usr/local/sbin/check_ng.sh
[root@test1 ~]# systemctl stop firewalld
[root@test1 ~]# setenforce 0

如果你master上的nginx是源码编译的，那么对应脚本上启动nginx的命令要做相应修改，此外master上的防火墙和selinux必须关闭，否则keepalived无法拉起nginx。

keepalived的日志文件记录在/var/log/messages文件内

[root@test1 data]# less /var/log/messages
...
Jan 16 19:58:06 test1 Keepalived_vrrp[5547]: Registering gratuitous ARP shared channel
Jan 16 19:58:06 test1 Keepalived_vrrp[5547]: Opening file '/etc/keepalived/keepalived.conf'.
Jan 16 19:58:06 test1 kernel: show_signal_msg: 53 callbacks suppressed
Jan 16 19:58:06 test1 kernel: keepalived[5547]: segfault at 0 ip           (null) sp 00007fff063621b8 error 14 in libgcc_s-4.8.5-20150702.so.1[7fd2356f4000+15000]
Jan 16 19:58:06 test1 Keepalived_vrrp[5547]: VRRP_Instance(VI_
1) removing protocol VIPs.
Jan 16 19:58:06 test1 Keepalived[4983]: Keepalived_vrrp exited due to segmentation fault (SIGSEGV).
Jan 16 19:58:06 test1 Keepalived[4983]:  Please report a bug at https://github.com/acassen/keepalived/issues Jan 16 19:58:06 test1 Keepalived[4983]:  and include this log from when keepalived started, what happened
Jan 16 19:58:06 test1 Keepalived[4983]:  immediately before the crash, and your configuration file.
Jan 16 19:58:06 test1 Keepalived[4983]: VRRP child process(5547) died: Respawning
Jan 16 19:58:06 test1 Keepalived[4983]: Starting VRRP child process, pid=5548
Jan 16 19:58:06 test1 Keepalived_vrrp[5548]: Registering Kernel netlink reflector
Jan 16 19:58:06 test1 Keepalived_vrrp[5548]: Registering Kernel netlink command channel
Jan 16 19:58:06 test1 Keepalived_vrrp[5548]: Registering gratuitous ARP shared channel
Jan 16 19:58:06 test1 Keepalived_vrrp[5548]: Opening file '/etc/keepalived/keepalived.conf'.
...

公有ip的查看

[root@test1 data]# ip addr
...
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
...
inet 192.168.65.100/32 scope global ens33
valid_lft forever preferred_lft forever
...

配置backup从服务器

修改配置文件

# 配置前关闭防火墙及selinux
[root@test1 ~]# systemctl stop firewalld
[root@test1 ~]# setenforce 0

[root@test2 ~]# cat /etc/keepalived/keepalived.conf
global_defs {
notification_email {
1245626656@qq.com
}
notification_email_from 1245626656@qq.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 {
# 配置为backup机
state BACKUP
interface ens33
# router_id与master一致
virtual_router_id 51
# 权重较master要小
priority 90
advert_int 1
authentication {
auth_type PASS
auth_pass test2
}
# 这样设置公有ip，master宕机后，backup机绑定
virtual_ipaddress {
192.168.65.100
}
track_script {
chk_nginx
}
}

配置检测脚本

[root@test2 ~]# 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`

if [ $n -eq "0" ]; then
# backup机上的nginx使用yum安装的，启动目录不同
systemctl start nginx
n2=`ps -C nginx --no-heading|wc -l`
# 执行启动nginx后发现nginx启动不成功，就关闭keepalived服务，并记录日志
if [ $n2 -eq "0"  ]; then
echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log
systemctl stop keepalived
fi
fi

# 配置权限
[root@test1 ~]# chmod 755 /usr/local/sbin/check_ng.sh

区分主从内的nginx

修改master上nginx默认主机的默认网页内容为“master web”；backup上nginx默认主页的内容为“backup web”;访问公有ip看显示的是哪个服务器的默认网页。

# 修改默认虚拟主机上的默认网页内容，这个要根据自己的实际情况修改
[root@test1 ~]# echo "master web server" > /data/wwwroot/default/index.html

# yum 安装的nginx的默认网页路径是/usr/share/nginx/html/index.html
[root@test2 ~]# echo "backup web server" > /usr/share/nginx/html/index.html

测试高可用

master信息

[root@test1 data]# curl -x127.0.0.1:80 test1.com
master web server
[root@test1 data]# curl -x127.0.0.1:80 test1.com -I
HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Tue, 16 Jan 2018 13:36:35 GMT
Content-Type: text/html
Content-Length: 18
Last-Modified: Tue, 16 Jan 2018 13:33:27 GMT
Connection: keep-alive
ETag: "5a5dff27-12"
Accept-Ranges: bytes
# 当前公用ip绑定在test1上
[root@test1 data]# ip addr
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:d0:81:f5 brd ff:ff:ff:ff:ff:ff
inet 192.168.65.133/24 brd 192.168.65.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.65.100/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::893d:23f6:69dd:1d54/64 scope link
valid_lft forever preferred_lft forever

backup信息

[root@test2 ~]# curl -x127.0.0.1:80 test2.com
backup web server
[root@test2 ~]# curl -x127.0.0.1:80 test2.com -I
HTTP/1.1 200 OK
Server: nginx/1.12.2
Date: Tue, 16 Jan 2018 13:35:49 GMT
Content-Type: text/html
Content-Length: 18
Last-Modified: Tue, 16 Jan 2018 13:35:33 GMT
Connection: keep-alive
ETag: "5a5dffa5-12"
Accept-Ranges: bytes

模拟主宕机：关闭master上的keepalived

模拟主恢复服务：重启master上的keepalived