title: 负载均衡之keepalived cover: https://img.paulzzh.com/touhou/random?97 date: 2020-04-12 14:08:31 categories: 分布式 toc: true tags: [分布式, 负载均衡, keepalived]
在前面介绍的LVS中容易发生单点故障的问题；当LVS或者RS挂掉时，后台的RS服务不再可靠。而通过部署keepalive可以达到检测单点故障，并达到自动切换LVS Server和剔除故障RS的效果。
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<!--more--> <!-- **目录:** --> <!-- toc --> <!-- <br/> -->本文在LVS中DR模型实战基础之上, 在LVS节点中配置Keepalive, 从而解决LVS的单点故障问题;
在解决HA问题时主要主要使用的是一台变多台, 此时有两种思路:
<font color="#f00">**而在LVS一台变多台时, 只能有一台对外提供服务(VIP只能配置在一台机器上对外提供服务)**</font>
在某台LVS挂掉后, VIP会切换到另外一台LVS继续提供服务;
而检测LVS的健康状况, 对LVS进行切换就是使用keepalived实现的;
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具体子容器的创建本篇不再赘述, 更多的是进行keepalived的说明
如中途遇到问题, 解决方法参考:
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Keepalived是Linux下面实现VRRP备份路由的高可靠性运行件。Keepalived是一个基于VRRP协议来实现的服务高可用方案，可以利用其来避免IP单点故障，类似的工具还有heartbeat、corosync、pacemaker。但是它一般不会单独出现，而是与其它负载均衡技术（如lvs、haproxy、nginx）一起工作来达到集群的高可用。
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简介: VRRP
VRRP全称 Virtual Router Redundancy Protocol，即 虚拟路由冗余协议。
可以认为它是实现路由器高可用的容错协议，即将N台提供相同功能的路由器组成一个路由器组(Router Group)，这个组里面有一个master和多个backup，但在外界看来就像一台一样，构成虚拟路由器，拥有一个虚拟IP（vip，也就是路由器所在局域网内其他机器的默认路由），占有这个IP的master实际负责ARP相应和转发IP数据包，组中的其它路由器作为备份的角色处于待命状态。
master会发组播消息，当backup在超时时间内收不到vrrp包时就认为master宕掉了，这时就需要根据VRRP的优先级来选举一个backup当master，保证路由器的高可用。
master会定期的向backup集群发送广播包，通报自己的健康状态。而backup在多个时间周期都未收到master的广播包时，就认为master已经挂掉，此时会根据序列号的高低马上推选一个新的master(在LVS的实践中会立刻在新的master中配置VIP)
当RS挂掉之后，在ipvsadm -ln列表中，会将具体的负载均衡RS条目标记为不可用，从而不再向此RS中分配请求负载包；
一旦keepalived再次感知到RS上线后，会再次将RS加入，标记为可用；
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注：RS的健康检测
keepalived通过向RS发送一个GET请求头，检测响应码是否返回200；
<font color="#f00">**不是使用ping!**</font>
<font color="#f00">**因为实际使用ping命令时连四层的基本都没有到! 仅仅使用了三层协议, 更别提建立握手!**</font>
此外，如果keepalived验证的是200的响应码，则对于一些跳转返回如3xx响应码也会被认为RS挂掉！
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使用下述命令创建一个叫做lvs_dr的子网络(上次已经创建):
docker network create --subnet=172.20.1.0/16 lvs_dr
网络规划为(在下方配置):
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为了考察keepalived实现了故障转移, 使用到了两个LVS
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然后在子网络中分别创建lvs, rs1, rs2三个子容器并启动:
docker run -d --privileged=true --name=lvs1 --net lvs_dr --ip 172.20.1.1 centos:7 /usr/sbin/init
docker run -d --privileged=true --name=lvs2 --net lvs_dr --ip 172.20.1.2 centos:7 /usr/sbin/init
docker run -d --privileged=true --name=rs1 --net lvs_dr --ip 172.20.1.10 centos:7 /usr/sbin/init
docker run -d --privileged=true --name=rs2 --net lvs_dr --ip 172.20.1.11 centos:7 /usr/sbin/init
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对于RS的配置和之前的配置完全相同, 具体步骤如下;
<font color="#f00">**需要注意的是: 必须先配置RS的响应和通告级别然后再去配置VIP**</font>
<font color="#f00">**否则, 先配置的VIP会直接被广播. 就失去了对外隐藏, 对内可见的性质!**</font>
下面以rs1为例配置arp_ignore和arp_announce文件:
[root@b2f5ab1b8b7d conf]# cd /proc/sys/net/ipv4/conf/
[root@b2f5ab1b8b7d conf]# ll
total 0
dr-xr-xr-x 1 root root 0 Apr 10 08:03 all
dr-xr-xr-x 1 root root 0 Apr 10 08:03 default
dr-xr-xr-x 1 root root 0 Apr 10 08:03 eth0
dr-xr-xr-x 1 root root 0 Apr 10 08:03 lo
[root@b2f5ab1b8b7d conf]# cd eth0/
[root@b2f5ab1b8b7d eth0]# echo 1 > arp_ignore
[root@b2f5ab1b8b7d eth0]# echo 2 > arp_announce
[root@b2f5ab1b8b7d eth0]# cat arp_ignore
1
[root@b2f5ab1b8b7d eth0]# cat arp_announce
2
上面修改了ech0目录下的配置信息
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<font color="#f00">**注: 在启动容器和交互时必须增加`--privileged=true`参数, 否则文件将为只读, 无法修改**</font>
如果后续还要添加新的机器, 可以通过修改all目录下的配置信息
[root@b2f5ab1b8b7d eth0]# cd ../all/
[root@b2f5ab1b8b7d all]# echo 1 > arp_ignore
[root@b2f5ab1b8b7d all]# echo 2 > arp_announce
这里继续以rs1为例对VIP(172.20.1.100)进行配置;
使用ifconfig配置如下:
[root@b2f5ab1b8b7d all]# ifconfig lo:1 172.20.1.100 netmask 255.255.255.255
[root@b2f5ab1b8b7d all]# ifconfig
eth0 Link encap:Ethernet HWaddr 02:42:AC:14:01:0A
inet addr:172.20.1.10 Bcast:172.20.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:32 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:4578 (4.4 KiB) TX bytes:0 (0.0 b)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
lo:1 Link encap:Local Loopback
inet addr:172.20.1.100 Mask:255.255.255.255
UP LOOPBACK RUNNING MTU:65536 Metric:1
<font color="#f00">**注: 将掩码地址配置为四个255**</font>
两台RS都经过了上述配置之后, 安装httpd服务;
yum install httpd -y
然后在/var/www/html目录下创建一个主页分别表示当前RS的主页
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为了显示负载均衡的效果, 两个RS的内容不同. 而在实际生成环境, 应当部署相同的Server镜像
对于rs1:
[root@b2f5ab1b8b7d all]# cd /var/www/html/
[root@b2f5ab1b8b7d html]# vi index.html
[root@b2f5ab1b8b7d html]# cat index.html
from 172.20.1.10
对于rs2:
[root@953d5b5e1201 /]# vi /var/www/html/index.html
[root@953d5b5e1201 /]# cat /var/www/html/index.html
from 172.20.1.11
然后启动两个服务:
# CentOS 7中, 启动服务
[root@88528e94e720 /]# systemctl start httpd
# 在CentOS 6.x中使用下面
[root@b2f5ab1b8b7d html]# service httpd start
Starting httpd: httpd: Could not reliably determine the server's fully qualified domain name, using 172.20.1.10 for ServerName [ OK ]
此时可以访问172.20.1.10和172.20.1.11, 会分别显示:
# http://172.20.1.10/
from 172.20.1.10
# http://172.20.1.11/
from 172.20.1.11
但此时访问# http://172.20.1.100/会访问失败, 因为LVS还尚未配置;
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在LVS容器中可以不安装ipvsadm软件（推荐安装，可以使用ipvsadm -lnc查看ipvs日志记录）
使用yum安装keepalived即可：
yum install -y keepalived
启动：
# CentOS 7中
systemctl start keepalived
# CentOS 6中
service keepalived start
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启动前应先修改配置
配置文件：/etc/keepalived/keepalived.conf
日志文件：/var/log/message
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在配置keepalived之前，先清除之前ipvs的配置：
ipvsadm -C
修改keepalived配置：
配置172.20.1.10为主机master：
[root@9517ef4219ec keepalived]# cd /etc/keepalived/
# 配置文件备份
[root@9517ef4219ec keepalived]# cp keepalived.conf keepalived.conf.bak
# 修改配置文件
[root@9517ef4219ec keepalived]# vi keepalived.conf
! Configuration File for keepalived
# 全局配置，无需修改
global_defs {
notification_email {
acassen@firewall.loc
failover@firewall.loc
sysadmin@firewall.loc
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 192.168.200.1
smtp_connect_timeout 30
# 可设置lvs的id，在一个网络内唯一
router_id LVS_DEVEL
vrrp_skip_check_adv_addr
vrrp_strict
vrrp_garp_interval 0
vrrp_gna_interval 0
}
vrrp_instance VI_1 {
# 主机配置，从机为BACKUP
state MASTER
# 网卡名称
interface eth0
virtual_router_id 51
# 权重值,值越大，优先级越高
# backup设置比master小, 这样就能在master宕机后将backup变为master
# 而master恢复后就再抢回master位置
priority 100
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
# 同一网段VIP配置
virtual_ipaddress {
# 根据docker规划的可知：
# ip: 172.20.1.100 mask: 255.255.0.0(16)
# 设备为eth0，标签为eth0:1
172.20.1.100/16 dev eth0 label eth0:1
}
}
# virtual_server VIP port
virtual_server 172.20.1.100 80 {
delay_loop 6
# 负载均衡策略
lb_algo rr
# 负载均衡模型
lb_kind DR
# 子网掩码
nat_mask 255.255.0.0
# 保持连接的时间
persistence_timeout 0
protocol TCP
# RS配置
real_server 172.20.1.10 80 {
# 负载均衡权重
weight 1
# 健康检测配置
# 使用HTTP_GET探活, 如果使用了HTTPS则为SSL
HTTP_GET {
# 探活url和探活条件
url {
path /
status_code 200
}
# 重试时间/次数
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
# RS2配置
virtual_server 172.20.1.100 80 {
delay_loop 6
lb_algo rr
lb_kind DR
nat_mask 255.255.0.0
persistence_timeout 0
protocol TCP
real_server 172.20.1.11 80 {
weight 1
HTTP_GET {
url {
path /
status_code 200
}
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
将172.20.1.11配置为从节点, 与上面配置类似, 只需修改vrrp_instance VI_1中的配置:
state BACKUP表示为从节点;priority 50 表示从节点的权重;其他配置和主节点一致;
配置完毕之后开启两个LVS容器中的keepalived
systemctl start keepalived
然后打开浏览器输入VIP(172.20.1.100)；
使用Ctrl+F5刷新，则会依次显示from 172.20.1.10和from 172.20.1.11；
说明keepalived部署成功；
在master中查看ipvs负载均衡情况:
[root@9517ef4219ec keepalived]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.20.1.100:80 rr
-> 172.20.1.10:80 Route 1 0 0
-> 172.20.1.11:80 Route 1 0 0
可以看到两个RS服务器;
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停止一个rs容器中的httpd服务, 如rs1容器
systemctl stop httpd
此时经历一个keepalived探活的过程(探活期间rs1中的服务将无法访问)
使用Ctrl+F5刷新，则仅会显示from 172.20.1.11；
在master节点查看ipvs:
[root@9517ef4219ec keepalived]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.20.1.100:80 rr
-> 172.20.1.11:80 Route 1 0 0
可以看到只剩下一个172.20.1.11一个RS;
重新开启RS1中的httpd服务:
systemctl start httpd
在等待一会, 使用Ctrl+F5刷新，则又会依次显示from 172.20.1.10和from 172.20.1.11；
在master节点查看ipvs:
[root@9517ef4219ec keepalived]# ipvsadm -ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP 172.20.1.100:80 rr
-> 172.20.1.10:80 Route 1 0 0
-> 172.20.1.11:80 Route 1 0 0
可以看到两个RS均在负载均衡列表中;
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在一般情况下IPVS很难挂掉(因为IPVS属于内核功能, 如果IPVS挂掉, 基本说明整个服务器挂掉了)
我们可以通过直接禁用lvs容器中的eth0物理接口实现:
[root@9517ef4219ec /]# ifconfig eth0 down
[root@9517ef4219ec /]# ifconfig
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
此时访问172.20.1.100, 并使用Ctrl+F5刷新，仍会显示两个网页;
而在另一台主机上会自动创建eth0:1, 如下:
[root@bb1945fadef5 /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.2 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
RX packets 584 bytes 57801 (56.4 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 384 bytes 30766 (30.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.100 netmask 255.255.0.0 broadcast 0.0.0.0
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
再次使用ifconfig up启用lvs1中的eth0:
[root@9517ef4219ec /]# ifconfig eth0 up
[root@9517ef4219ec /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.1 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:01 txqueuelen 0 (Ethernet)
RX packets 454 bytes 55619 (54.3 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 700 bytes 48787 (47.6 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.100 netmask 255.255.0.0 broadcast 0.0.0.0
ether 02:42:ac:14:01:01 txqueuelen 0 (Ethernet)
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
则172.20.1.1又成为master, 所以会自动配上eth0:1子接口;
而在lvs2(172.20.1.2)中又会自动删除eth0:1子接口:
[root@bb1945fadef5 /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.2 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
RX packets 991 bytes 102255 (99.8 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 821 bytes 63459 (61.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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使用kill -9杀死在lvs1中的keepalive进程:
# 查看并杀死keepalived进程
[root@9517ef4219ec /]# ps -fe | grep keep
root 1153 1 0 09:13 ? 00:00:00 /usr/sbin/keepalived -D
root 1154 1153 0 09:13 ? 00:00:00 /usr/sbin/keepalived -D
root 1155 1153 0 09:13 ? 00:00:00 /usr/sbin/keepalived -D
root 1189 1131 0 09:24 pts/0 00:00:00 grep --color=auto keep
[root@9517ef4219ec /]# kill -9 1153
[root@9517ef4219ec /]# ps -fe | grep keep
root 1192 1131 0 09:25 pts/0 00:00:00 grep --color=auto keep
# 查看lvs1中已不存在eth0:1子接口
[root@9517ef4219ec /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.1 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:01 txqueuelen 0 (Ethernet)
RX packets 944 bytes 118425 (115.6 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1570 bytes 110567 (107.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
而lvs2已被提升为MASTER:
[root@bb1945fadef5 /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.2 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
RX packets 1563 bytes 161846 (158.0 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1295 bytes 100717 (98.3 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.20.1.100 netmask 255.255.0.0 broadcast 0.0.0.0
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
此时再次启用lvs1中的keepalived服务:
[root@9517ef4219ec /]# systemctl start keepalived
[root@9517ef4219ec /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.1 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:01 txqueuelen 0 (Ethernet)
RX packets 1119 bytes 128261 (125.2 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1587 bytes 111562 (108.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth0:1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.100 netmask 255.255.0.0 broadcast 0.0.0.0
ether 02:42:ac:14:01:01 txqueuelen 0 (Ethernet)
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
则lvs1再次变为MASTER, 而lvs2降为BACKUP:
[root@bb1945fadef5 /]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.20.1.2 netmask 255.255.0.0 broadcast 172.20.255.255
ether 02:42:ac:14:01:02 txqueuelen 0 (Ethernet)
RX packets 1849 bytes 197178 (192.5 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1747 bytes 133196 (130.0 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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