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所属分类：linux技术
keepalived高可用
keepalived是什么？
Keepalived 软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：Nginx、Haproxy、MySQL等）的高可用解决方案软件。
Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，它能够保证当个别节点宕机时，整个网络可以不间断地运行。
所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。
Keepalived官网：http://www.keepalived.org/
Keepalived的重要功能
keepalived 有三个重要的功能，分别是：
-
管理LVS负载均衡软件
-
实现LVS集群节点的健康检查
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作为系统网络服务的高可用性
keepalived高可用故障转移的原理
Keepalived 高可用服务之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。
在 Keepalived 服务正常工作时，主 Master 节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备 Backup 节点自己还活看，当主 Master 节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master 节点的心跳了，于是调用自身的接管程序，接管主 Master 节点的 IP 资源及服务。而当主 Master 节点恢复时，备 Backup 节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。
keepalived原理
Keepalived高可用对之间是通过VRRP通信的，因此，我们从 VRRP开始了解起：
- VRRP,全称 Virtual Router Redundancy Protocol,中文名为虚拟路由冗余协议，VRRP的出现是为了解决静态路由的单点故障。
- VRRP是通过一种竟选协议机制来将路由任务交给某台 VRRP路由器的。
- VRRP用 IP多播的方式（默认多播地址（224.0.0.18))实现高可用对之间通信。
- 工作时主节点发包，备节点接包，当备节点接收不到主节点发的数据包的时候，就启动接管程序接管主节点的资源。备节点可以有多个，通过优先级竞选，但一般 Keepalived系统运维工作中都是一对。
- VRRP使用了加密协议加密数据，但Keepalived官方目前还是推荐用明文的方式配置认证类型和密码。
介绍完 VRRP,接下来我再介绍一下 Keepalived服务的工作原理：
Keepalived高可用是通过 VRRP 进行通信的， VRRP是通过竞选机制来确定主备的，主的优先级高于备，因此，工作时主会优先获得所有的资源，备节点处于等待状态，当主挂了的时候，备节点就会接管主节点的资源，然后顶替主节点对外提供服务。
在 Keepalived 服务之间，只有作为主的服务器会一直发送 VRRP 广播包,告诉备它还活着，此时备不会枪占主，当主不可用时，即备监听不到主发送的广播包时，就会启动相关服务接管资源，保证业务的连续性.接管速度最快可以小于1秒。
演示：
实验环境：
| 主机名 | 系统 | IP | VIP |
|---|---|---|---|
| lxmaster.example.com | Red Hat Enterprise Linux release 8.2 | 192.168.100.110/24 | 192.168.100.200/32 |
| lxbackup.example.com | Red Hat Enterprise Linux release 8.2 | 192.168.100.120/24 |
配置IP
#Master主节点 [root@lxmaster ~]# nmcli eth0: 已连接 到 eth0 "VMware VMXNET3" ethernet (vmxnet3), 00:0C:29:E7:7F:F3, 硬件, mtu 1500 ip4 默认 inet4 192.168.100.110/24 route4 192.168.100.0/24 route4 0.0.0.0/0 inet6 fe80::20c:29ff:fee7:7ff3/64 route6 fe80::/64 route6 ff00::/8 #backup备份节点 [root@lxbackup ~]# nmcli ens160: 已连接 到 ens160 "VMware VMXNET3" ethernet (vmxnet3), 00:0C:29:88:DC:C6, 硬件, mtu 1500 ip4 默认 inet4 192.168.100.120/24 route4 192.168.100.0/24 route4 0.0.0.0/0 inet6 fe80::20c:29ff:fe88:dcc6/64 route6 fe80::/64 route6 ff00::/8 关闭防火墙
#Master主节点 [root@lxmaster ~]# systemctl stop firewalld.service [root@lxmaster ~]# systemctl disable firewalld.service Removed /etc/systemd/system/multi-user.target.wants/firewalld.service. Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service. [root@lxmaster ~]# vim /etc/selinux/ [root@lxmaster ~]# vim /etc/selinux/config ... SELINUX=disabled ... #backup备份节点 [root@lxbackup ~]# systemctl stop firewalld.service [root@lxbackup ~]# systemctl disable firewalld.service Removed /etc/systemd/system/multi-user.target.wants/firewalld.service. Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service. [root@lxbackup ~]# vim /etc/selinux/config ... SELINUX=disabled ... 安装keeppalived
#Mster主节点 [root@lxmaster ~]# yum -y install vim wget gcc gcc-c++ [root@lxmaster ~]# yum -y install keepalived #backup节点 [root@lxbackup ~]# yum -y install vim wget gcc gcc-c++ [root@lxbackup ~]# yum -y install keepalived 安装nginx
#Master主节点 [root@lxmaster ~]# yum -y install nginx [root@lxmaster ~]# echo " master node" > /usr/share/nginx/html/index.html [root@lxmaster ~]# systemctl restart nginx.service [root@lxmaster ~]# systemctl enable nginx.service Created symlink /etc/systemd/system/multi-user.target.wants/nginx.service → /usr/lib/systemd/system/nginx.service. #backup节点 [root@lxbackup ~]# yum -y install nginx [root@lxbackup ~]# echo "backup node" > /usr/share/nginx/html/index.html [root@lxbackup ~]# systemctl enable --now nginx.service Created symlink /etc/systemd/system/multi-user.target.wants/nginx.service → /usr/lib/systemd/system/nginx.service. 测试
#Master主节点 [root@lxmaster ~]# curl localhost master node #backup节点 [root@lxbackup ~]# curl localhost backup node 配置keepalived
#Master主节点 [root@lxmaster ~]# cd /etc/keepalived/ [root@lxmaster keepalived]# cp keepalived.conf keepalived.conf.bak [root@lxmaster keepalived]# vim keepalived.conf ! Configuration File for keepalived global_defs { router id lx01 } vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.100.200 } } virtual_server 192.168.100.200 80 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.100.110 80 { weight 1 TCP_CHECK{ connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.200.3 1358 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } #重启keepalived [root@lxmaster keepalived]# systemctl restart keepalived.service [root@lxmaster keepalived]# systemctl enable keepalived.service Created symlink /etc/systemd/system/multi-user.target.wants/keepalived.service → /usr/lib/systemd/system/keepalived.service. #backup备份节点 [root@lxbackup ~]# cd /etc/keepalived/ [root@lxbackup keepalived]# cp keepalived.conf keepalived.conf.bak [root@lxbackup keepalived]# vim keepalived.conf ! Configuration File for keepalived global_defs { router_id lx02 } vrrp_instance VI_1 { state BACKUP interface ens160 virtual_router_id 51 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.100.200 } } virtual_server 192.168.100.200 80 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.100.110 80 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.100.120 80 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } [root@lxbackup keepalived]# systemctl restart keepalived.service [root@lxbackup keepalived]# systemctl enable keepalived.service Created symlink /etc/systemd/system/multi-user.target.wants/keepalived.service → /usr/lib/systemd/system/keepalived.service. 在master中配置VIP
[root@lxmaster ~]# vim /etc/sysconfig/network-scripts/ifcfg-eth0 ... IPADDR1=192.168.100.200 PREFIX1=32 [root@lxmaster ~]# systemctl restart NetworkManager [root@lxmaster ~]# nmcli connection up eth0 连接已成功激活（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/4） [root@lxmaster ~]# ip a ... eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 00:0c:29:e7:7f:f3 brd ff:ff:ff:ff:ff:ff inet 192.168.100.110/24 brd 192.168.100.255 scope global noprefixroute eth0 valid_lft forever preferred_lft forever inet 192.168.100.200/32 scope global noprefixroute eth0 valid_lft forever preferred_lft forever ... 编写脚本
#Master主节点 [root@lxmaster scripts]# vim check.sh #!/bin/bash nginx_status=`ps -ef | grep -v "grep" | grep "nginx" | wc -l` if [ $nginx_status -lt 1 ];then systemctl stop keepalived fi [root@lxmaster scripts]# vim notify.sh #!/bin/bash VIP=$2 sendmail () { subject="${VIP}'s server keepalived state is translate" content="`date +'%F %T'`: `hostname`'s state change to master" echo $content | mail -s "$subject" abc@163.com } case "$1" in master) nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'bnginxb'|wc -l) if [ $nginx_status -lt 1 ];then systemctl start nginx fi sendmail ;; backup) nginx_status=$(ps -ef|grep -Ev "grep|$0"|grep 'bnginxb'|wc -l) if [ $nginx_status -gt 0 ];then systemctl stop nginx fi ;; *) echo "Usage:$0 master|backup VIP" ;; esac [root@lxmaster scripts]# chmod +x check.sh [root@lxmaster scripts]# chmod +x notify.sh 再次配置keepalived
#Master主节点 [root@lxmaster scripts]# vim /etc/keepalived/keepalived.conf ! Configuration File for keepalived global_defs { router id lx01 } vrrp_script nginx_check { script "/scripts/check.sh" interval 10 weight -20 } vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.100.200 } track_script{ nginx_check } notify_master "/scripts/notify.sh master 192.168.100.200" notify_backup "/scripts/notify.sh backup 192.168.100.200" } virtual_server 192.168.100.200 80 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.100.110 80 { weight 1 TCP_CHECK{ connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.200.3 1358 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } [root@lxmaster scripts]# systemctl restart keepalived.service #backup节点 [root@lxbackup ~]# vim /etc/keepalived/keepalived.conf ! Configuration File for keepalived global_defs { router_id lx02 } vrrp_script nginx_check { script "/scripts/check.sh" interval 10 weight -20 } vrrp_instance VI_1 { state BACKUP interface ens160 virtual_router_id 51 priority 90 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.100.200 } notify_master "/scripts/notify.sh master 192.168.100.200" notify_backup "/scripts/notify.sh backup 192.168.100.200" } virtual_server 192.168.100.200 80 { delay_loop 6 lb_algo rr lb_kind DR persistence_timeout 50 protocol TCP real_server 192.168.100.110 80 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } real_server 192.168.100.120 80 { weight 1 TCP_CHECK { connect_port 80 connect_timeout 3 nb_get_retry 3 delay_before_retry 3 } } } [root@lxbackup ~]# systemctl restart keepalived.service 模拟故障
[root@lxmaster ~]# systemctl restart nginx.service [root@lxmaster ~]# systemctl enable nginx #此时查看备份节点80端口暂未开启 [root@lxbackup ~]# ss -tanl State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 5 127.0.0.1:631 0.0.0.0:* LISTEN 0 128 [::]:22 [::]:* LISTEN 0 5 [::1]:631 [::]:* 
[root@lxmaster ~]# systemctl stop nginx.service [root@lxmaster ~]# systemctl restart keepalived.service #再次查看备份节点80端口已开启 [root@lxbackup ~]# ss -tanl State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 0.0.0.0:80 0.0.0.0:* LISTEN 0 128 0.0.0.0:22 0.0.0.0:* LISTEN 0 5 127.0.0.1:631 0.0.0.0:* LISTEN 0 128 [::]:80 [::]:* LISTEN 0 128 [::]:22 [::]:* LISTEN 0 5 [::1]:631 [::]:* 
