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keepalive简介

keepalive为LVS应用延伸的高可用服务。lvs的调度器无法做高可用。但keepalive不是为lvs专门集群服务的，也可以为其他的的代理服务器做高可用。
keepalive在lvs的高可用集群，主调度器和备调度器(可以有多个) 一主两备或一主一备。

VRRP: keepalived是基于vrrp协议实现Ivs服务的高可用。解决了调度器单节点的故障问题。
VRRP协议：提高网络路由器的可靠性开发的一种协议。

vrrp工作原理
·选举出主和备，预先设定主备的优先级。主的优先级较高，备的优先级低，一旦开启服务器，优先级高的，会自定抢占主的位置。
·VRRP组播通信: 224.0.0.18 VRRP协议当中的主备服务器通过组播地进行通信，交换主备服务器之间的运行状态。主服务会周期性的发送vrrp协议报文，告诉备：主的当前状态。
·主备切换：主服务器发生故障,或者不可达，VRRP协议会把请求转义到备服务器。通过组播地址，VRRP可以迅速的通知其他服务器发生了主备切换，确保新的主服务器可以正常处理客户端的请求。
·故障恢复: 一旦主服务器恢复通信，由组播地址进行通信，发现在恢复的主服务器优先级更高，会抢占原主服务器的位置，成为主服务器，调度和接受请求。

keepalive工作原理

主调度器能够正常运行时，由主调度器进行后端真实服务器的分配处理。其余的备用调度器处于冗余状态。
不参与集群的运转。主调度器故障无法运行，备调度器才会承担主调度器的工作。
一旦主调度恢复工作，继续由主调度器进行处理，备调度器又成了冗余。

keepalive的体系模块:

全局模块：core模块，负载整个keepalived启

动加载和维护
                  VRRP模块：实现vrrp协议，主备切换
                  check模块：负责后端真实服务器健康检查，配置真实服务器的模块当中。

安装keepalived                yum -y install keepalived ipvsadm

vim /etc/keepalived/keepalived.conf下配置说明

·邮箱地：smtp_server
·主备服务的id,主和备的id不能一致：router_id_01
·取消严格遵守vrrp协议功能，不取消VIP无法连接：#vrrp_strict
·标识主身份：state MASTER
·指定vip地址的物理接口：interface ens33
·虚拟路由器的id号：virtual_router_id 10
·发送报文的间隔时间：advert_int 30
·指定集群的vip地址：virtual_ipaddress
·健康检查的间隔时间：delay_loop 6		单位s
·负载均衡的调度算法：lb algo rr
·指定lvs集群的工作方式(要大写)：lb_kind NAT
·连接保持：persistence_timeout 50 	单位s
·VIP模块：virtual server 192.168.233.100 80 
·后端真实服务器的轮询权重：real_server 192.168.233.30 80 
·检测目标的端口号：connect_port 80
·连接超时时间：connect_timeout 3		单位s
·重试的次数：nb_get_retry 3
·重试间隔秒数：delay_before_retry 4

实验(LVS-DR)-keepalive

主192.168.10.10

备192.168.10.40

web服务器

192.168.10.20----nginx

192.168.10.30----nginx

客户端访问：任意一台

主192.168.10.10

yum -y install keepalived ipvsadm
vim /etc/keepalived/keepalived.conf
.............smtp_server 127.0.0.1router_id LVS_01vrrp_strict 注释掉interface ens33persistence_timeout 0virtual_ipaddress {192.168.10.99
}
修改上面的，并删掉最后一个下面所有的内容，并添加以下内容virtual_server 192.168.10.99 80 {delay_loop 6lb_algo rrlb_kind DRpersistence_timeout 0protocol TCPreal_server 192.168.10.20 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 4}
}
real_server 192.168.10.30 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 4}
}
}.............systemctl restart keepalived.service
systemctl restart ipvsadm.service
ipvsadm-save > /etc/sysconfig/ipvsadm
systemctl restart ipvsadm.service
ipvsadm -ln
ipvsadm-save > /etc/sysconfig/ipvsadm
systemctl restart ipvsadm.servicevim /etc/sysctl.conf 
.....................net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0.....................sysctl -p 立即加载

备192.168.10.40

yum -y install keepalived ipvsadm
vim /etc/keepalived/keepalived.conf
.............smtp_server 127.0.0.1router_id LVS_02priority 90vrrp_strict 注释掉state BACKUPinterface ens33persistence_timeout 0virtual_ipaddress {192.168.10.99
}
修改上面的，并删掉最后一个下面所有的内容，并添加以下内容virtual_server 192.168.10.99 80 {delay_loop 6lb_algo rrlb_kind DRpersistence_timeout 0protocol TCPreal_server 192.168.10.20 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 4}
}
real_server 192.168.10.30 80 {weight 1TCP_CHECK {connect_port 80connect_timeout 3nb_get_retry 3delay_before_retry 4}
}
}.............systemctl restart keepalived.service
systemctl restart ipvsadm.service
ipvsadm-save > /etc/sysconfig/ipvsadm
systemctl restart ipvsadm.service
ipvsadm -ln
ipvsadm-save > /etc/sysconfig/ipvsadm
systemctl restart ipvsadm.servicevim /etc/sysctl.conf 
.....................net.ipv4.ip_forward = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0.....................sysctl -p 立即加载

web服务器

192.168.10.20

192.168.10.30

vim /etc/sysconfig/network-scripts/ifcfg-lo:0
.........................DEVICE=lo:0
IPADDR=192.168.10.99
NETMASK=255.255.255.255
ONBOOT=yes.........................重启lo:0网卡
ifup ifcfg-lo:0 绑定vip
route add -host 192.168.10.99 dev lo:0vim /etc/sysctl.conf
...................net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2...................
sysctl -p

结果

停止主的
systemctl stop ipvsadm.service
systemctl stop keepalived.servicevip漂移到备服务器
ip addr 看页面访问服务正常

keepalive基于nginx高可用

主192.168.10.10--nginx

yum -y install keepalived
vim /etc/keepalived/keepalived.conf
...................
global_defs模块中smtp_server 127.0.0.1router_id LVS_01#vrrp_strict在global和vrrp_instance之间加
.......
vrrp_script check_nginx {script "/opt/check_nginx.sh"interval 5
}
.......vrrp_instance模块中virtual_ipaddress {192.168.10.99
}
vrrp_instance内最后加
track_script {check_nginx
}...................vrrp_instance模块后的都删除chmod 777 /opt/check_nginx.sh
systemctl restart keepalived.service

传递nginx的状态
vim /opt/check_nginx.sh#!/bin/bash
/usr/bin/curl -I http://localhost &> /dev/null
if [ $? -ne 0 ]
thensystemctl stop keepalived
fi

备192.168.10.20--nginx

yum -y install keepalived
vim /etc/keepalived/keepalived.conf
...................
global_defs模块中smtp_server 127.0.0.1router_id LVS_02#vrrp_strict在global和vrrp_instance之间加
.......
vrrp_script check_nginx {script "/opt/check_nginx.sh"interval 5
}
.......vrrp_instance模块中state BACKUP
priority 90
virtual_ipaddress {192.168.10.99
}
vrrp_instance内最后加
track_script {check_nginx
}...................vrrp_instance模块后的都删除chmod 777 /opt/check_nginx.sh
systemctl restart keepalived.service

传递nginx的状态
vim /opt/check_nginx.sh#!/bin/bash
/usr/bin/curl -I http://localhost &> /dev/null
if [ $? -ne 0 ]
thensystemctl stop keepalived
fi

结果：

当主故障后切换到备，主要恢复需要

主故障
systemctl stop nginx.service主恢复需要
systemctl restart nginx.service
systemctl restart keepalived.service