第十八章 Linux集群
18.1 集群介绍
Linux集群根据功能划分为两大类：高可用和负载均衡。
高可用集群
高可用集群通常为2台服务器，一台工作，另一台作为冗余，当提供服务的机器宕机时，冗余将接替继续提供服务。
实现高可用的开源软件有：heartbeat、Keepalived，其中heartbeat已无人维护，所以今后使用Keepalived来搭建高可用集群。
负载均衡集群
负载均衡集群，需要有1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台，所以负载均衡集群至少要3台服务器。
实现负载均衡的开源软件有：LVS、Keepalived、haproxy、nginx；商业软件有：F5、Netscaler。
18.2 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，这个小组会有1个master角色和N（N≥1）个backup角色。
Keepalived有三个模块：core、check、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负责实现vrrp协议。
18.3-18.5 用Keepalived配置高可用集群（上）
操作环境：
两台虚拟机：
master：192.168.230.135；
backup：192.168.230.145；
准备工作
master：
[root@cham002 ~]# yum install -y keepalived
[root@cham002 ~]# /usr/local/nginx/sbin/nginx -v
nginx version: nginx/1.12.1
backup：
[root@test ~]# yum install -y keepalived
[root@test ~]# yum install -y nginx
[root@test ~]# nginx -v
nginx version: nginx/1.12.2
开始配置
配置master机器：
在此使用自定义的Keepalived配置文件脚本(先清空或删除自带配置文件脚本)。
[root@cham002 ~]# vim /etc/keepalived/keepalived.conf
global_defs {
notification_email {
[email protected]
} #定义故障提醒邮件接收地址（本实验用不到）
notification_email_from [email protected]
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL #定义故障提醒邮件发送地址（本实验用不到）
}
vrrp_script chk_nginx { #定义监控脚本
script "/usr/local/sbin/check_ng.sh" #指定服务健康检测（check）脚本
interval 3 #检测时间间隔
}
vrrp_instance VI_1 {
state MASTER #定义该服务的角色
interface ens33 #定义在本机中监听VIP的网卡
virtual_router_id 51 #虚拟路由id（同组中的服务器保持该id一致）
priority 100 #指定本机权重（决定优先级）
advert_int 1
authentication { #定义认证相关信息
auth_type PASS #认证类型为密码形式
auth_pass 123456 #定义认证密码
}
virtual_ipaddress { #定义VIP
192.168.230.100
}
track_script { #加载监控服务（脚本）
chk_nginx #注意此处服务名称要与上面监控脚本名称一致
}
}创建监控脚本：
[root@cham002 ~]# 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`
if [ $n2 -eq "0" ]; then
echo "$d nginx down,keepalived will stop" >> /var/log/check_ng.log
systemctl stop keepalived #在此停止Keepalived服务是为了避免发生脑裂
fi
fi
更改脚本权限：
[root@cham002 ~]# chmod 755 !$
chmod 755 /usr/local/sbin/check_ng.sh
启动Keepalived服务：
[root@cham002 ~]# systemctl start keepalived
检测服务状态：
[root@cham002 ~]# ps aux |grep keep
root 4915 0.0 0.1 120720 1400 ? Ss 18:51 0:00 /usr/sbin/keepalived -D
root 4916 0.0 0.3 127460 3276 ? S 18:51 0:00 /usr/sbin/keepalived -D
root 4917 0.0 0.2 131656 3024 ? S 18:51 0:00 /usr/sbin/keepalived -D
root 4966 0.0 0.0 112680 976 pts/1 S+ 18:52 0:00 grep --color=auto keep
[root@cham002 ~]# ps aux |grep nginx
root 2302 0.0 0.2 46840 2956 ? Ss 01:08 0:00 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
nobody 4763 0.0 0.4 48764 4164 ? S 18:25 0:00 nginx: worker process
nobody 4764 0.0 0.4 48764 4164 ? S 18:25 0:00 nginx: worker process
root 4986 0.0 0.0 112684 976 pts/1 S+ 18:52 0:00 grep --color=auto nginx
[root@cham002 ~]# date
2018年 01月 24日 星期三 18:54:09 CST
注：由以上检测状态可知关闭nginx服务之后Keepalived会再次自动启动nginx服务
[root@cham002 ~]# /etc/init.d/nginx stop
Stopping nginx (via systemctl): [ 确定 ]
[root@cham002 ~]# !ps
ps aux |grep nginx
root 2302 0.0 0.2 46840 2956 ? Ss 01:08 0:00 nginx: master process /usr/local/nginx/sbin/nginx -c /usr/local/nginx/conf/nginx.conf
nobody 4763 0.0 0.4 48764 4164 ? S 18:25 0:00 nginx: worker process
nobody 4764 0.0 0.4 48764 4164 ? S 18:25 0:00 nginx: worker process
root 5175 0.0 0.0 112684 976 pts/1 S+ 18:53 0:00 grep --color=auto nginx
注：由以上检测状态可知关闭nginx服务之后Keepalived会再次自动启动nginx服务说明： “脑裂”，即当master宕机后仍然未释放VIP，同时backup接替master提供服务要使用同一VIP，因而导致两台机器争占同一VIP导致服务紊乱，所以当master宕机后需要关闭其Keepalived服务来避免脑裂现象发生。Keepalived服务的日志位置：/var/log/messages。
查看网卡信息：
[root@cham002 ~]# ip add
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:b6:9f:e3 brd ff:ff:ff:ff:ff:ff
inet 192.168.230.135/24 brd 192.168.230.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.188.100/32 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.230.150/24 brd 192.168.230.255 scope global secondary ens33:0
valid_lft forever preferred_lft forever
inet6 fe80::6f15:52d3:ebeb:e193/64 scope link
valid_lft forever preferred_lft forever
3: ens37: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:b6:9f:ed brd ff:ff:ff:ff:ff:ff
inet 192.168.100.1/24 brd 192.168.100.255 scope global ens37
valid_lft forever preferred_lft forever
inet6 fe80::1801:cbbb:ebcc:89a3/64 scope link
valid_lft forever preferred_lft forever
说明： 在此不能使用ifconfig查看，ens33中增加了一个IP：192.168.188.100/32。
检查防火墙
[root@cham002 ~]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
[root@cham002 ~]# getenforce
Disabled
配置backup机器：
检查防火墙
[root@test ~]# systemctl stop firewalld
[root@test ~]# iptables -nvL
Chain INPUT (policy ACCEPT 92 packets, 6136 bytes)
pkts bytes target prot opt in out source destination
Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
Chain OUTPUT (policy ACCEPT 50 packets, 5200 bytes)
pkts bytes target prot opt in out source destination
[root@test ~]# setenforce 0
[root@test ~]# getenforce
Permissive
配置Keepalived：
同样使用自定义脚本。
[root@test ~]# vim /etc/keepalived/keepalived.conf
global_defs {
notification_email {
[email protected]
}
notification_email_from [email protected]
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 { #只有该部分与master有区别
state BACKUP #角色
interface ens33
virtual_router_id 51
priority 90 #权重
advert_int 1
authentication {
auth_type PASS
auth_pass 123456
}
virtual_ipaddress {
192.168.230.100
}
track_script {
chk_nginx
}
} 说明： 如果是多台服务器，权重决定了master宕机后，backup接管master角色的顺序。
创建监控脚本：
[root@test ~]# 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
~
[root@test ~]# chmod 755 !$
chmod 755 /usr/local/sbin/check_ng.sh
说明： 该检测脚本中与master检测脚本的区别在于：systemctl start nginx，即nginx的启动方式，因为在backup服务器中是使用yum安装的nginx，默认添加到系统服务中。
[root@test ~]# systemctl start keepalived
[root@test ~]# ps aux |grep keep
root 10695 0.0 0.1 120704 1396 ? Ss 20:19 0:00 /usr/sbin/keepalived -D
root 10696 0.0 0.3 127444 3260 ? S 20:19 0:00 /usr/sbin/keepalived -D
root 10697 0.0 0.2 131640 2840 ? S 20:19 0:00 /usr/sbin/keepalived -D
root 10728 0.0 0.0 112664 968 pts/1 R+ 20:19 0:00 grep --color=auto keep
测试
宕机前
master：
[root@cham002 ~]# cat /usr/local/nginx/conf/vhost/aaa.com.conf
server
{
listen 80 default_server;
server_name aaa.com;
index index.html index.htm index.php;
root /data/wwwroot/default;
location ~ \.php$
{
include fastcgi_params;
fastcgi_pass unix:/tmp/champ.sock;
#fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
fastcgi_param SCRIPT_FILENAME /data/wwwroot/default$fastcgi_script_name;
}
}
[root@cham002 ~]# cat /data/wwwroot/default/index.html
This is the default sete.
[root@cham002 ~]# vim /data/wwwroot/default/index.html
master This is the default sete.
[root@cham002 ~]#
backup：
[root@test ~]# cat /usr/share/nginx/html/index.html
[root@test ~]# vim /usr/share/nginx/html/index.html
backup backup.
使用VIP访问：
此时默认访问到master服务器。
master宕机后：
[root@cham002 ~]# systemctl stop keepalived
[root@cham002 ~]# 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:b6:9f:e3 brd ff:ff:ff:ff:ff:ff
inet 192.168.230.135/24 brd 192.168.230.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.230.150/24 brd 192.168.230.255 scope global secondary ens33:0
valid_lft forever preferred_lft forever
inet6 fe80::6f15:52d3:ebeb:e193/64 scope link
valid_lft forever preferred_lft forever
3: ens37: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:b6:9f:ed brd ff:ff:ff:ff:ff:ff
inet 192.168.100.1/24 brd 192.168.100.255 scope global ens37
valid_lft forever preferred_lft forever
inet6 fe80::1801:cbbb:ebcc:89a3/64 scope link
valid_lft forever preferred_lft forever
[root@cham002 ~]#
backup:
[root@test ~]# 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:29:50:f9:44 brd ff:ff:ff:ff:ff:ff
inet 192.168.230.145/24 brd 192.168.230.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.230.100/32 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::9b07:b28d:f5e9:d107/64 scope link
valid_lft forever preferred_lft forever
[root@test ~]# tail /var/log/messages
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
注： 恢复master上的Keepalived服务后,会由master服务器为该集群提供服务。如下：
[root@cham002 ~]# systemctl start keepalived
[root@cham002 ~]# 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:b6:9f:e3 brd ff:ff:ff:ff:ff:ff
inet 192.168.230.135/24 brd 192.168.230.255 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.230.100/32 scope global ens33
valid_lft forever preferred_lft forever
inet 192.168.230.150/24 brd 192.168.230.255 scope global secondary ens33:0
valid_lft forever preferred_lft forever
inet6 fe80::6f15:52d3:ebeb:e193/64 scope link
valid_lft forever preferred_lft forever
3: ens37: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:b6:9f:ed brd ff:ff:ff:ff:ff:ff
inet 192.168.100.1/24 brd 192.168.100.255 scope global ens37
valid_lft forever preferred_lft forever
inet6 fe80::1801:cbbb:ebcc:89a3/64 scope link
在看看日志变化
[root@test ~]# tail /var/log/messages
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
[root@test ~]# tail /var/log/messages
Jan 28 20:44:17 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) Sending/queueing gratuitous ARPs on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:44:22 test Keepalived_vrrp[12877]: Sending gratuitous ARP on ens33 for 192.168.230.100
Jan 28 20:47:29 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) Received advert with higher priority 100, ours 90
Jan 28 20:47:29 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) Entering BACKUP STATE
Jan 28 20:47:29 test Keepalived_vrrp[12877]: VRRP_Instance(VI_1) removing protocol VIPs.
在生产环境中，可能会用到2-3台backup角色, vim /etc/keepalived/keepalived.conf
这里面的权重调成不通级别。权重越高优先级越高！除了nginx服务的话，还可以做MySQL的高可用集群服务。