大纲
一、前言
二、Keepalived 详解
三、环境准备
四、LVS+Keepalived 实现高可用的前端负载均衡器
一、前言
这篇文章是前几篇文章的总结，我们先简单的总结一下我们前面讲解的内容，前面我们讲解了，LVS（负载均衡器）、Heartbeat、Corosync、Pacemaker、Web高可用集群、MySQL高可用集群、DRDB、iscsi、gfs2、cLVM等，唯一没有讲解的就是LVS可用，也就是前端高可用，我们这一篇博文主要讲解内容。在说这个之前我们得和大家讨论一个问题，也是好多博友问的问题。Heartbeat、Corosync、Keepalived这三个集群组件我们到底选哪个好，首先我想说明的是，Heartbeat、Corosync是属于同一类型，Keepalived与Heartbeat、Corosync，根本不是同一类型的。Keepalived使用的vrrp协议方式，虚拟路由冗余协议 (Virtual Router Redundancy Protocol，简称VRRP)；Heartbeat或Corosync是基于主机或网络服务的高可用方式；简单的说就是，Keepalived的目的是模拟路由器的高可用，Heartbeat或Corosync的目的是实现Service的高可用。所以一般Keepalived是实现前端高可用，常用的前端高可用的组合有，就是我们常见的LVS+Keepalived、Nginx+Keepalived、HAproxy+Keepalived。而Heartbeat或Corosync是实现服务的高可用，常见的组合有Heartbeat v3(Corosync)+Pacemaker+NFS+Httpd 实现Web服务器的高可用、Heartbeat v3(Corosync)+Pacemaker+NFS+MySQL 实现MySQL服务器的高可用。总结一下，Keepalived中实现轻量级的高可用，一般用于前端高可用，且不需要共享存储，一般常用于两个节点的高可用。而Heartbeat(或Corosync)一般用于服务的高可用，且需要共享存储，一般用于多节点的高可用。这个问题我们说明白了，又有博友会问了，那heartbaet与corosync我们又应该选择哪个好啊，我想说我们一般用corosync，因为corosync的运行机制更优于heartbeat，就连从heartbeat分离出来的pacemaker都说在以后的开发当中更倾向于corosync，所以现在corosync+pacemaker是最佳组合。但说实话我对于软件没有任何倾向性，所以我把所有的集群软件都和大家说了一下，我认为不管什么软件，只要它能存活下来都有它的特点和应用领域，只有把特定的软件放在特定的位置才能发挥最大的作用，那首先我们得对这个软件有所有了解。学习一种软件的最好方法，就是去查官方文档。好了说了那么多希望大家有所收获，下面我们来说一说keepalived。
二、Keepalived 详解
1.Keepalived 定义
Keepalived 是一个基于VRRP协议来实现的LVS服务高可用方案，可以利用其来避免单点故障。一个LVS服务会有2台服务器运行Keepalived，一台为主服务器（MASTER），一台为备份服务器（BACKUP），但是对外表现为一个虚拟IP，主服务器会发送特定的消息给备份服务器，当备份服务器收不到这个消息的时候，即主服务器宕机的时候， 备份服务器就会接管虚拟IP，继续提供服务，从而保证了高可用性。Keepalived是VRRP的完美实现，因此在介绍keepalived之前，先介绍一下VRRP的原理。
2.VRRP 协议简介
在现实的网络环境中，两台需要通信的主机大多数情况下并没有直接的物理连接。对于这样的情况，它们之间路由怎样选择？主机如何选定到达目的主机的下一跳路由，这个问题通常的解决方法有二种：
在主机上使用动态路由协议(RIP、OSPF等)
在主机上配置静态路由
很明显，在主机上配置动态路由是非常不切实际的，因为管理、维护成本以及是否支持等诸多问题。配置静态路由就变得十分流行，但路由器(或者说默认网关default gateway)却经常成为单点故障。VRRP的目的就是为了解决静态路由单点故障问题，VRRP通过一竞选(election)协议来动态的将路由任务交给LAN中虚拟路由器中的某台VRRP路由器。
3.VRRP 工作机制
在一个VRRP虚拟路由器中，有多台物理的VRRP路由器，但是这多台的物理的机器并不能同时工作，而是由一台称为MASTER的负责路由工作，其它的都是BACKUP，MASTER并非一成不变，VRRP让每个VRRP路由器参与竞选，最终获胜的就是MASTER。MASTER拥有一些特权，比如，拥有虚拟路由器的IP地址，我们的主机就是用这个IP地址作为静态路由的。拥有特权的MASTER要负责转发发送给网关地址的包和响应ARP请求。
VRRP通过竞选协议来实现虚拟路由器的功能，所有的协议报文都是通过IP多播(multicast)包(多播地址224.0.0.18)形式发送的。虚拟路由器由VRID(范围0-255)和一组IP地址组成，对外表现为一个周知的MAC地址。所以，在一个虚拟路由 器中，不管谁是MASTER，对外都是相同的MAC和IP(称之为VIP)。客户端主机并不需要因为MASTER的改变而修改自己的路由配置，对客户端来说，这种主从的切换是透明的。
在一个虚拟路由器中，只有作为MASTER的VRRP路由器会一直发送VRRP通告信息(VRRPAdvertisement message)，BACKUP不会抢占MASTER，除非它的优先级(priority)更高。当MASTER不可用时(BACKUP收不到通告信息)， 多台BACKUP中优先级最高的这台会被抢占为MASTER。这种抢占是非常快速的(<1s)，以保证服务的连续性。由于安全性考虑，VRRP包使用了加密协议进行加密。
4.VRRP 工作流程
(1).初始化：
路由器启动时，如果路由器的优先级是255(最高优先级，路由器拥有路由器地址)，要发送VRRP通告信息，并发送广播ARP信息通告路由器IP地址对应的MAC地址为路由虚拟MAC，设置通告信息定时器准备定时发送VRRP通告信息，转为MASTER状态；否则进入BACKUP状态，设置定时器检查定时检查是否收到MASTER的通告信息。
(2).Master
设置定时通告定时器；
用VRRP虚拟MAC地址响应路由器IP地址的ARP请求；
转发目的MAC是VRRP虚拟MAC的数据包；
如果是虚拟路由器IP的拥有者，将接受目的地址是虚拟路由器IP的数据包，否则丢弃；
当收到shutdown的事件时删除定时通告定时器，发送优先权级为0的通告包，转初始化状态；
如果定时通告定时器超时时，发送VRRP通告信息；
收到VRRP通告信息时，如果优先权为0，发送VRRP通告信息；否则判断数据的优先级是否高于本机，或相等而且实际IP地址大于本地实际IP，设置定时通告定时器，复位主机超时定时器，转BACKUP状态；否则的话，丢弃该通告包；
(3).Backup
设置主机超时定时器；
不能响应针对虚拟路由器IP的ARP请求信息；
丢弃所有目的MAC地址是虚拟路由器MAC地址的数据包；
不接受目的是虚拟路由器IP的所有数据包；
当收到shutdown的事件时删除主机超时定时器，转初始化状态；
主机超时定时器超时的时候，发送VRRP通告信息，广播ARP地址信息，转MASTER状态；
收到VRRP通告信息时，如果优先权为0，表示进入MASTER选举；否则判断数据的优先级是否高于本机，如果高的话承认MASTER有效，复位主机超时定时器；否则的话，丢弃该通告包；
5.ARP查询处理
当内部主机通过ARP查询虚拟路由器IP地址对应的MAC地址时，MASTER路由器回复的MAC地址为虚拟的VRRP的MAC地址，而不是实际网卡的 MAC地址，这样在路由器切换时让内网机器觉察不到；而在路由器重新启动时，不能主动发送本机网卡的实际MAC地址。如果虚拟路由器开启的ARP代理 (proxy_arp)功能，代理的ARP回应也回应VRRP虚拟MAC地址；好了VRRP的简单讲解就到这里，我们下来讲解一下Keepalived的案例。
三、环境准备
1.操作系统
CentOS 6.4 X86_64
2.软件版本
ipvsadm.x86_64 0:1.25-10.el6
keepalived.x86_64 0:1.2.7-3.el6
httpd-2.2.15-29.el6.centos.x86_64
3.实验拓扑
4.时间同步
node1:
[root@node1 ~]# ntpdate 202.120.2.101
node2:
[root@node2 ~]# ntpdate 202.120.2.101
master:
[root@master ~]# ntpdate 202.120.2.101
slave:
[root@slave ~]# ntpdate 202.120.2.101
5.主机名互相解析
node1:
[root@node1 ~]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.18.201 node1 192.168.18.202 node2
node2:
[root@node2 ~]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 192.168.18.201 node1 192.168.18.202 node2
6.安装yum源
node1:
[root@node1 ~]# rpm -ivh /pub/epel/6/x86_64/epel-release-6-8.noarch.rpm[root@node1 ~]# rpm -ivh /elrepo-release-6-5.el6.elrepo.noarch.rpm
node2:
[root@node2 ~]# rpm -ivh /pub/epel/6/x86_64/epel-release-6-8.noarch.rpm[root@node2 ~]# rpm -ivh /elrepo-release-6-5.el6.elrepo.noarch.rpm
master:
[root@master ~]# rpm -ivh /pub/epel/6/x86_64/epel-release-6-8.noarch.rpm[root@master ~]# rpm -ivh /elrepo-release-6-5.el6.elrepo.noarch.rpm
slave:
[root@slave ~]# rpm -ivh /pub/epel/6/x86_64/epel-release-6-8.noarch.rpm[root@slave ~]# rpm -ivh /elrepo-release-6-5.el6.elrepo.noarch.rpm
四、LVS+Keepalived 实现高可用的前端负载均衡器
node1:
1.安装httpd
[root@node1 ~]# yum install -y httpd
2.配置httpd
[root@node1 ~]# vim /var/www/html/index.html<h1></h1>
3.启动httpd
[root@node1 ~]# service httpd start
4.测试
5.设置开机自启动
[root@node1 ~]# chkconfig httpd on [root@node1 ~]# chkconfig httpd --list httpd 0:关闭 1:关闭 2:启用 3:启用 4:启用 5:启用 6:关闭
6.配置node1
[root@node1 ~]# mkdir src [root@node1 ~]# cd src/ [root@node1 src]# vim realserver.sh#!/bin/bash # # Script to start LVS DR real server. # description: LVS DR real server # . /etc/rc.d/init.d/functionsVIP=192.168.18.200 #修改你的VIP host=`/bin/hostname`case "$1" in start) # Start LVS-DR real server on this machine. /sbin/ifconfig lo down /sbin/ifconfig lo up echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce/sbin/ifconfig lo:0 $VIP broadcast $VIP netmask 255.255.255.255 up /sbin/route add -host $VIP dev lo:0;; stop)# Stop LVS-DR real server loopback device(s). /sbin/ifconfig lo:0 down echo 0 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/lo/arp_announce echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce;; status)# Status of LVS-DR real server. islothere=`/sbin/ifconfig lo:0 | grep $VIP` isrothere=`netstat -rn | grep "lo:0" | grep $VIP` if [ ! "$islothere" -o ! "isrothere" ];then # Either the route or the lo:0 device # not found. echo "LVS-DR real server Stopped." else echo "LVS-DR real server Running." fi ;; *) # Invalid entry. echo "$0: Usage: $0 {start|status|stop}" exit 1 ;; esac [root@node1 src]# chmod +x realserver.sh [root@node1 src]# ll 总用量 4 -rwxr-xr-x 1 root root 1485 8月 22 10:18 realserver.sh[root@node1 src]# ./realserver.sh start
7.查看配置
[root@node1 src]# ifconfig eth0Link encap:Ethernet HWaddr 00:0C:29:11:92:E4 inet addr:192.168.18.201 Bcast:192.168.18.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe11:92e4/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:115061 errors:0 dropped:0 overruns:0 frame:0 TX packets:14979 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:43448483 (41.4 MiB) TX bytes:1224926 (1.1 MiB)lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:2 errors:0 dropped:0 overruns:0 frame:0 TX packets:2 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:168 (168.0 b) TX bytes:168 (168.0 b)lo:0Link encap:Local Loopback inet addr:192.168.18.200 Mask:255.255.255.255 UP LOOPBACK RUNNING MTU:16436 Metric:1[root@node1 src]# route -n Kernel IP routing table DestinationGateway Genmask Flags Metric Ref Use Iface 192.168.18.200 0.0.0.0 255.255.255.255 UH 00 0 lo 192.168.18.0 0.0.0.0 255.255.255.0 U00 0 eth0 169.254.0.00.0.0.0 255.255.0.0U1002 0 0 eth0 0.0.0.0 192.168.18.254 0.0.0.0 UG 00 0 eth0[root@node1 src]# cat /proc/sys/net/ipv4/conf/lo/arp_ignore 1 [root@node1 src]# cat /proc/sys/net/ipv4/conf/lo/arp_announce 2 [root@node1 src]# cat /proc/sys/net/ipv4/conf/all/arp_ignore 1 [root@node1 src]# cat /proc/sys/net/ipv4/conf/all/arp_announce2
好了，node1到这里基本配置完成，下面我们来配置node2。
node2:
1.安装httpd
[root@node2 ~]# yum install -y httpd
2.配置httpd
[root@node2 ~]# vim /var/www/html/index.html<h1></h1>
3.启动httpd
[root@node2 ~]# service httpd start
4.测试
5.设置开机自启动
[root@node2 ~]# chkconfig httpd on [root@node2 ~]# chkconfig httpd --list httpd 0:关闭 1:关闭 2:启用 3:启用 4:启用 5:启用 6:关闭
6.配置node2
[root@node2 ~]# mkdir src [root@node2 ~]# cd src/ [root@node2 src]# vim realserver.sh#!/bin/bash # # Script to start LVS DR real server. # description: LVS DR real server # . /etc/rc.d/init.d/functionsVIP=192.168.18.200 host=`/bin/hostname`case "$1" in start) # Start LVS-DR real server on this machine. /sbin/ifconfig lo down /sbin/ifconfig lo up echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce/sbin/ifconfig lo:0 $VIP broadcast $VIP netmask 255.255.255.255 up /sbin/route add -host $VIP dev lo:0;; stop)# Stop LVS-DR real server loopback device(s). /sbin/ifconfig lo:0 down echo 0 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/lo/arp_announce echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce;; status)# Status of LVS-DR real server. islothere=`/sbin/ifconfig lo:0 | grep $VIP` isrothere=`netstat -rn | grep "lo:0" | grep $VIP` if [ ! "$islothere" -o ! "isrothere" ];then # Either the route or the lo:0 device # not found. echo "LVS-DR real server Stopped." else echo "LVS-DR real server Running." fi ;; *) # Invalid entry. echo "$0: Usage: $0 {start|status|stop}" exit 1 ;; esac[root@node2 src]# chmod +x realserver.sh [root@node2 src]# ./realserver.sh start
7.查看配置
[root@node2 src]# ifconfig eth0Link encap:Ethernet HWaddr 00:0C:29:B8:DF:6A inet addr:192.168.18.202 Bcast:192.168.18.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:feb8:df6a/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:110545 errors:0 dropped:0 overruns:0 frame:0 TX packets:10461 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:32853789 (31.3 MiB) TX bytes:889109 (868.2 KiB)lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:6 errors:0 dropped:0 overruns:0 frame:0 TX packets:6 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:616 (616.0 b) TX bytes:616 (616.0 b)lo:0Link encap:Local Loopback inet addr:192.168.18.200 Mask:255.255.255.255 UP LOOPBACK RUNNING MTU:16436 Metric:1[root@node2 src]# route -n Kernel IP routing table DestinationGateway Genmask Flags Metric Ref Use Iface 192.168.18.200 0.0.0.0 255.255.255.255 UH 00 0 lo 192.168.18.0 0.0.0.0 255.255.255.0 U00 0 eth0 169.254.0.00.0.0.0 255.255.0.0U1002 0 0 eth0 0.0.0.0 192.168.18.254 0.0.0.0 UG 00 0 eth0[root@node2 src]# cat /proc/sys/net/ipv4/conf/lo/arp_ignore 1 [root@node2 src]# cat /proc/sys/net/ipv4/conf/lo/arp_announce 2 [root@node2 src]# cat /proc/sys/net/ipv4/conf/all/arp_ignore 1 [root@node2 src]# cat /proc/sys/net/ipv4/conf/all/arp_announce 2
好了，到这里node2也基本配置完成。下面我们来配置master与slave。
masterg与slave:
1.安装keepalived与ipvsadm
[root@master ~]# yum install -y keepalived ipvsadm[root@slave ~]# yum install -y keepalived ipvsadm
2.修改配置文件
[root@master ~]# cat /etc/keepalived/keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ #配置管理员邮箱 } notification_email_from root #配置发件人 smtp_server 127.0.0.1 #配置邮件服务器 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_instance VI_1 { state MASTER #配置模式 interface eth0 virtual_router_id 51 priority 101 #配置优先级 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 #配置虚拟IP地址 } }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 #persistence_timeout 50 protocol TCPreal_server 192.168.18.201 80 { #配置realaserver weight 1 HTTP_GET { #监控配置 url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } }
3.将配置文件同步到slave
[root@master ~]# scp /etc/keepalived/keepalived.conf root@192.168.18.207:/etc/keepalived/
4.简单修改一下slave配置文件
[root@slave keepalived]# cat keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_instance VI_1 { state BACKUP #修改为BACKUP interface eth0 virtual_router_id 51 priority 100 #修改优先级 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 #persistence_timeout 50 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } }
5.启动master与slave的keepalived服务
[root@master ~]# service keepalived start 正在启动 keepalived： [确定][root@slave ~]# service keepalived start 正在启动 keepalived： [确定]
6.查看一下LVS状态
[root@master ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.18.200:80 rr -> 192.168.18.201:80 Route 100 -> 192.168.18.202:80 Route 100
7.测试
8.模拟故障
(1).停止一下node1
[root@node1 src]# service httpd stop 停止 httpd： [确定]
(2).查看一下的lvs
[root@master ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.18.200:80 rr -> 192.168.18.202:80 Route 100
(3).测试一下
(4).查看一下邮件
(5).重新启动一下node1
[root@node1 src]# service httpd start 正在启动 httpd： [确定]
(6).再查看一下lvs状态
[root@master ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.18.200:80 rr -> 192.168.18.201:80 Route 100 -> 192.168.18.202:80 Route 100
(7).再查看一下邮件
(8).关闭master上keepalived
[root@master ~]# service keepalived stop 停止 keepalived： [确定] [root@master ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn
(9).查看一下slave状态
[root@slave ~]# ip addr show 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:f9:e6:26 brd ff:ff:ff:ff:ff:ff inet 192.168.18.207/24 brd 192.168.18.255 scope global eth0 inet 192.168.18.200/32 scope global eth0 inet6 fe80::20c:29ff:fef9:e626/64 scope link valid_lft forever preferred_lft forever [root@slave ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.18.200:80 rr -> 192.168.18.201:80 Route 100 -> 192.168.18.202:80 Route 100
(10).再次测试一下
注，大家可以看到，经过上面的演示我们现在LVS的高可用即前端负载均衡的高可用，同时实现对后端realserver监控，也实现后端realserver宕机时会给管理员发送邮件。但还有几个问题我们还没有解决，问题如下:
所有realserver都down机，怎么处理？是不是用户就没法打开，还是提供一下维护页面。
怎么完成维护模式keepalived切换？
如何在keepalived故障时，发送警告邮件给指定的管理员？
9.所有realserver都down机，怎么处理？
问题：在集群中如果所有real server全部宕机了，客户端访问时就会出现错误页面，这样是很不友好的，我们得提供一个维护页面来提醒用户，服务器正在维护，什么时间可以访问等，下面我们就来解决一下这个问题。解决方案有两种，一种是提供一台备用的real server当所有的服务器宕机时，提供维护页面，但这样做有点浪费服务器。另一种就是在负载均衡器上提供维护页面，这样是比较靠谱的，也比较常用。下面我们就来具体操作一下。
(1).master与slave安装上httpd
[root@master ~]# yum install -y httpd[root@slave ~]# yum install -y httpd
(2).配置维护页面
[root@master ~]# vim /var/www/html/index.html Website is currently under maintenance, please come back later![root@slave ~]# vim /var/www/html/index.html Website is currently under maintenance, please come back later!
(3).启动httpd服务并测试
[root@master ~]# service httpd start 正在启动 httpd： [确定][root@slave ~]# service httpd start 正在启动 httpd： [确定]
(4).修改配置文件
master:
[root@master ~]# cat /etc/keepalived/keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80 #增加一行sorry_server }
slave:
[root@slave ~]# cat /etc/keepalived/keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80 #增加一行sorry_server }
(5).关闭所有的real server并重新启动一下master与slave的keepalived
[root@node1 ~]# service httpd stop 停止 httpd： [确定][root@node2 ~]# service httpd stop 停止 httpd： [确定][root@master ~]# service keepalived restart 停止 keepalived： [确定] 正在启动 keepalived： [确定][root@slave ~]# service keepalived restart 停止 keepalived： [确定] 正在启动 keepalived： [确定]
(6).查看一下lvs
[root@master ~]# ipvsadm -L -n IP Virtual Server version 1.2.1 (size=4096) Prot LocalAddress:Port Scheduler Flags -> RemoteAddress:Port Forward Weight ActiveConn InActConn TCP 192.168.18.200:80 rr -> 127.0.0.1:80 Local 100
(7).测试
注，sorry_server测试成功，下面我们继续。
10.怎么完成维护模式keepalived切换？
问题：我们一般进行主从切换测试时都是关闭keepalived或关闭网卡接口，有没有一种方法能实现在不关闭keepalived下或网卡接口来实现维护呢？方法肯定是有的，在keepalived新版本中，支持脚本vrrp_srcipt，具体如何使用大家可以man keepalived.conf查看。下面我们来演示一下具体怎么实现。
(1).定义脚本
vrrp_srcipt chk_schedown { script "[ -e /etc/keepalived/down ] && exit 1 || exit 0" interval 1 #监控间隔 weight -5 #减小优先级 fall 2 #监控失败次数 rise 1 #监控成功次数 }
(2).执行脚本
track_script {chk_schedown #执行chk_schedown脚本}
(3).修改配置文件
master:
[root@master ~]# cat /etc/keepalived/keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_script chk_schedown { #定义vrrp执行脚本 script "[ -e /etc/keepalived/down ] && exit 1 || exit 0" #查看是否有down文件，有就进入维护模式 interval 1 #监控间隔时间 weight -5 #降低优先级 fall 2 #失败次数 rise 1 #成功数次 }vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } track_script { #执行脚本 chk_schedown } }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80 }
slave:
[root@slave ~]# cat /etc/keepalived/keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_script chk_schedown { script "[ -e /etc/keepalived/down ] && exit 1 || exit 0" interval 1 weight -5 fall 2 rise 1 }vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } track_script { chk_schedown }}virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80
(4).测试
master:
[root@master keepalived]# touch down #新建一下down文件[root@master keepalived]# ll 总用量 4 -rw-r--r-- 1 root root 0 8月 22 13:39 down -rw-r--r-- 1 root root 1317 8月 22 13:35 keepalived.conf[root@master keepalived]# tail -f /var/log/messages #查看一下日志 Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) Entering MASTER STATE Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) setting protocol VIPs. Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.18.200 Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) Received higher prio advert Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) Entering BACKUP STATE Aug 22 13:43:52 master Keepalived_vrrp[1]: VRRP_Instance(VI_1) removing protocol VIPs. Aug 22 13:43:52 master Keepalived_healthcheckers[12002]: Netlink reflector reports IP 192.168.18.200 added Aug 22 13:43:52 master Keepalived_healthcheckers[12002]: Netlink reflector reports IP 192.168.18.200 removed Aug 22 13:43:52 master Keepalived_healthcheckers[12002]: SMTP alert successfully sent. Aug 22 13:43:52 master Keepalived_healthcheckers[12002]: SMTP alert successfully sent. ^C [root@master keepalived]# ip add show #查看VIP 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:4b:a1:85 brd ff:ff:ff:ff:ff:ff inet 192.168.18.208/24 brd 192.168.18.255 scope global eth0 inet6 fe80::20c:29ff:fe4b:a185/64 scope link valid_lft forever preferred_lft forever
slave:
[root@slave ~]# ip addr show #查看一下VIP已转移到slave上 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:f9:e6:26 brd ff:ff:ff:ff:ff:ff inet 192.168.18.207/24 brd 192.168.18.255 scope global eth0 inet 192.168.18.200/32 scope global eth0 inet6 fe80::20c:29ff:fef9:e626/64 scope link valid_lft forever preferred_lft forever
好了，自写监测脚本，完成维护模式切换，到这里就演示成功，下面我们来解决最后一个问题，就是keepalived主从切换的邮件通告。
11.如何在keepalived故障时(或主备切换时)，发送警告邮件给指定的管理员？
(1).keepalived通知脚本进阶示例
下面的脚本可以接受选项，其中
-s, --service SERVICE,...：指定服务脚本名称，当状态切换时可自动启动、重启或关闭此服务；
-a, --address VIP: 指定相关虚拟路由器的VIP地址；
-m, --mode {mm|mb}：指定虚拟路由的模型，mm表示主主，mb表示主备；它们表示相对于同一种服务而方，其VIP的工作类型；
-n, --notify {master|backup|fault}：指定通知的类型，即vrrp角色切换的目标角色；
-h, --help：获取脚本的使用帮助；
#!/bin/bash # Author: freeloda # description: An example of notify script # Usage: notify.sh -m|--mode {mm|mb} -s|--service SERVICE1,... -a|--address VIP -n|--notify {master|backup|falut} -h|--helpcontact='1521076067@'helpflag=0 serviceflag=0 modeflag=0 addressflag=0 notifyflag=0Usage() { echo "Usage: notify.sh [-m|--mode {mm|mb}] [-s|--service SERVICE1,...] <-a|--address VIP> <-n|--notify {master|backup|falut}>" echo "Usage: notify.sh -h|--help" }ParseOptions() { local I=1; if [ $# -gt 0 ]; then while [ $I -le $# ]; do case $1 in -s|--service) [ $# -lt 2 ] && return 3 serviceflag=1 services=(`echo $2|awk -F"," '{for(i=1;i<=NF;i++) print $i}'`) shift 2 ;; -h|--help) helpflag=1 return 0 shift ;; -a|--address) [ $# -lt 2 ] && return 3 addressflag=1 vip=$2 shift 2 ;; -m|--mode) [ $# -lt 2 ] && return 3 mode=$2 shift 2 ;; -n|--notify) [ $# -lt 2 ] && return 3 notifyflag=1 notify=$2 shift 2 ;; *) echo "Wrong options..." Usage return 7 ;; esac done return 0 fi }#workspace=$(dirname $0)RestartService() { if [ ${#@} -gt 0 ]; then for I in $@; do if [ -x /etc/rc.d/init.d/$I ]; then /etc/rc.d/init.d/$I restart else echo "$I is not a valid service..." fi done fi }StopService() { if [ ${#@} -gt 0 ]; then for I in $@; do if [ -x /etc/rc.d/init.d/$I ]; then /etc/rc.d/init.d/$I stop else echo "$I is not a valid service..." fi done fi }Notify() { mailsubject="`hostname` to be $1: $vip floating" mailbody="`date '+%F %H:%M:%S'`, vrrp transition, `hostname` changed to be $1." echo $mailbody | mail -s "$mailsubject" $contact }# Main Function ParseOptions $@ [ $? -ne 0 ] && Usage && exit 5[ $helpflag -eq 1 ] && Usage && exit 0if [ $addressflag -ne 1 -o $notifyflag -ne 1 ]; then Usage exit 2 fimode=${mode:-mb}case $notify in 'master') if [ $serviceflag -eq 1 ]; then RestartService ${services[*]} fi Notify master ;; 'backup') if [ $serviceflag -eq 1 ]; then if [ "$mode" == 'mb' ]; then StopService ${services[*]} else RestartService ${services[*]} fi fi Notify backup ;; 'fault') Notify fault ;; *) Usage exit 4 ;; esac
(2).在keepalived.conf配置文件中，其调用方法如下所示：
notify_master "/etc/keepalived/notify.sh -n master -a 192.168.18.200"
notify_backup "/etc/keepalived/notify.sh -n backup -a 192.168.18.200"
notify_fault "/etc/keepalived/notify.sh -n fault -a 192.168.18.200"
(3).修改配置文件
master:
[root@master keepalived]# cat keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_script chk_schedown { script "[ -e /etc/keepalived/down ] && exit 1 || exit 0" interval 1 weight -5 fall 2 rise 1 }vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 101 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } track_script { chk_schedown }#增加以下三行 notify_master "/etc/keepalived/notify.sh -n master -a 192.168.18.200" notify_backup "/etc/keepalived/notify.sh -n backup -a 192.168.18.200" notify_fault "/etc/keepalived/notify.sh -n fault -a 192.168.18.200" }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80 }
slave:
[root@slave keepalived]# cat keepalived.conf ! Configuration File for keepalivedglobal_defs { notification_email { 15251076067@ } notification_email_from root smtp_server 127.0.0.1 smtp_connect_timeout 30 router_id LVS_DEVEL }vrrp_script chk_schedown { script "[ -e /etc/keepalived/down ] && exit 1 || exit 0" interval 1 weight -5 fall 2 rise 1 }vrrp_instance VI_1 { state BACKUP interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.18.200 } track_script { chk_schedown }#增加以下三行 notify_master "/etc/keepalived/notify.sh -n master -a 192.168.18.200" notify_backup "/etc/keepalived/notify.sh -n backup -a 192.168.18.200" notify_fault "/etc/keepalived/notify.sh -n fault -a 192.168.18.200" }virtual_server 192.168.18.200 80 { delay_loop 6 lb_algo rr lb_kind DR nat_mask 255.255.255.0 protocol TCPreal_server 192.168.18.201 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } real_server 192.168.18.202 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 2 nb_get_retry 3 delay_before_retry 1 } } sorry_server 127.0.0.1 80 }
(4).增加脚本
[root@slave keepalived]# pwd /etc/keepalived [root@slave keepalived]# vim notify.sh[root@slave keepalived]# cat notify.sh #!/bin/bash # Author: freeloda # description: An example of notify script # Usage: notify.sh -m|--mode {mm|mb} -s|--service SERVICE1,... -a|--address VIP -n|--notify {master|backup|falut} -h|--helpcontact='15251076067@' helpflag=0 serviceflag=0 modeflag=0 addressflag=0 notifyflag=0Usage() { echo "Usage: notify.sh [-m|--mode {mm|mb}] [-s|--service SERVICE1,...] <-a|--address VIP> <-n|--notify {master|backup|falut}>" echo "Usage: notify.sh -h|--help" }ParseOptions() { local I=1; if [ $# -gt 0 ]; then while [ $I -le $# ]; do case $1 in -s|--service) [ $# -lt 2 ] && return 3 serviceflag=1 services=(`echo $2|awk -F"," '{for(i=1;i<=NF;i++) print $i}'`) shift 2 ;; -h|--help) helpflag=1 return 0 shift ;; -a|--address) [ $# -lt 2 ] && return 3 addressflag=1 vip=$2 shift 2 ;; -m|--mode) [ $# -lt 2 ] && return 3 mode=$2 shift 2 ;; -n|--notify) [ $# -lt 2 ] && return 3 notifyflag=1 notify=$2 shift 2 ;; *) echo "Wrong options..." Usage return 7 ;; esac done return 0 fi }#workspace=$(dirname $0)RestartService() { if [ ${#@} -gt 0 ]; then for I in $@; do if [ -x /etc/rc.d/init.d/$I ]; then /etc/rc.d/init.d/$I restart else echo "$I is not a valid service..." fi done fi }StopService() { if [ ${#@} -gt 0 ]; then for I in $@; do if [ -x /etc/rc.d/init.d/$I ]; then /etc/rc.d/init.d/$I stop else echo "$I is not a valid service..." fi done fi }Notify() { mailsubject="`hostname` to be $1: $vip floating" mailbody="`date '+%F %H:%M:%S'`, vrrp transition, `hostname` changed to be $1." echo $mailbody | mail -s "$mailsubject" $contact }# Main Function ParseOptions $@ [ $? -ne 0 ] && Usage && exit 5[ $helpflag -eq 1 ] && Usage && exit 0if [ $addressflag -ne 1 -o $notifyflag -ne 1 ]; then Usage exit 2 fimode=${mode:-mb}case $notify in 'master') if [ $serviceflag -eq 1 ]; then RestartService ${services[*]} fi Notify master ;; 'backup') if [ $serviceflag -eq 1 ]; then if [ "$mode" == 'mb' ]; then StopService ${services[*]} else RestartService ${services[*]} fi fi Notify backup ;; 'fault') Notify fault ;; *) Usage exit 4 ;; esac
(5).给脚本增加执行权限
[root@slave keepalived]# chmod +x notify.sh
(6).将master上脚本复制到slave上
[root@slave keepalived]# scp -p notify.sh root@192.168.18.207:/etc/keepalived/
(7).测试一下脚本
[root@slave keepalived]# ./notify.sh -h Usage: notify.sh [-m|--mode {mm|mb}] [-s|--service SERVICE1,...] <-a|--address VIP> <-n|--notify {master|backup|falut}> Usage: notify.sh -h|--help [root@slave keepalived]# ./notify.sh --help Usage: notify.sh [-m|--mode {mm|mb}] [-s|--service SERVICE1,...] <-a|--address VIP> <-n|--notify {master|backup|falut}> Usage: notify.sh -h|--help [root@slave keepalived]# ./notify.sh -m mb -a 1.1.1.1 -n master
(8).查看一下邮件
注，大家可以看到成功收到邮件，测试成功。在模拟故障时先重启一下keepalived服务。
(9).模拟故障
[root@master keepalived]# ip addr show #查看一下VIP 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:4b:a1:85 brd ff:ff:ff:ff:ff:ff inet 192.168.18.208/24 brd 192.168.18.255 scope global eth0 inet 192.168.18.200/32 scope global eth0 inet6 fe80::20c:29ff:fe4b:a185/64 scope link valid_lft forever preferred_lft forever [root@master keepalived]# touch down #进入维护模式 [root@master keepalived]# ll 总用量 8 -rw-r--r-- 1 root root 0 8月 22 14:39 down -rw-r--r-- 1 root root 1543 8月 22 14:04 keepalived.conf -rwxr-xr-x 1 root root 2516 8月 22 14:15 notify.sh [root@master keepalived]# ip addr show #再次查看VIP 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:4b:a1:85 brd ff:ff:ff:ff:ff:ff inet 192.168.18.208/24 brd 192.168.18.255 scope global eth0 inet6 fe80::20c:29ff:fe4b:a185/64 scope link valid_lft forever preferred_lft forever[root@slave keepalived]# ip addr show #大家可以看到VIP成功移动到slave上 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 link/ether 00:0c:29:f9:e6:26 brd ff:ff:ff:ff:ff:ff inet 192.168.18.207/24 brd 192.168.18.255 scope global eth0 inet 192.168.18.200/32 scope global eth0 inet6 fe80::20c:29ff:fef9:e626/64 scope link valid_lft forever preferred_lft forever
(10).查看一下邮件
注，大家可以看到，主备切换时，会发送邮件报警，好了到这里所有演示全部完成。希望大家有所收获^_^……
