Keepalived LVS-DR单网络双活双主配置模式
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LVS集群采用IP负载均衡技术和基于内容请求分发技术。调度器具有很好的吞吐率,将请求均衡地转移到不同的服务器上执行,且调度器自动屏蔽掉服务器的故障,从而将一组服务器构成一个高性能的、高可用的虚拟服务器。整个服务器集群的结构对客户是透明的,而且无需修改客户端和服务器端的程序。为此,在设计时需要考虑系统的透明性、可伸缩性、高可用性和易管理性。
LVS有两个重要的组件:一个是IPVS,一个是IPVSADM。ipvs是LVS的核心组件,它本身只是一个框架,类似于iptables,工作于内核空间中。ipvsadm 是用来定义LVS的转发规则的,工作于用户空间中。
称为网络地址转换,实现起来比较简单,所有的RealServer集群节点和前端调度器Director都要在同一个子网中,这种模型可以实现端口映射,RealServer的操作系统可以是任意操作系统,前端的Director既要处理客户端发起的请求,又要处理后台RealServer的响应信息,将RealServer响应的信息再转发给客户端,前端Director很容易成为整个集群系统性能的瓶颈。通常情况下RealServer的IP地址(以下简成RIP)为私有地址,便于RealServer集群节点之间进行通信通常情况下前端的Director有两个IP地址,一个为VIP,是虚拟的IP地址,客户端向此IP地址发起请求。一个是DIP,是真正的Director的IP地址,RIP的网关要指向Director的DIP。
DR:直接路由(direct routing)模式,此种模式通过MAC地址转发工作,所有的RealServer集群节点和前端调度器Director都要在同一个物理网络中,此种模式不支持端口映射,此种模式的性能要优于LVS-NAT,RIP可以使用公网的IP,RIP的网关不能指向DIP。
优点:
相对LVS/NAT模式,DR模式不需要把返回的数据通过负载均衡转发,想要他发挥优势,那么就要相应的数据包的数量和长度远远大于请求数据包,幸运的是,大部分WEB服务都具备这样的特点,响应和请求并不对称,因此常用的WEB服务,都可以使用这种模式。
这种方式,负载均衡器不再是系统的瓶颈。如果你的负载均衡器只拥有100M的全双工网卡和带宽的话,通过集群的横向扩展也可以让整个系统达到1G的流量。
来自LVS官方站点的测试结果也告诉我们,LVS-DR可以容纳100台以上的实际应用服务器,对一般的服务而已,这样的表现足够了。
不足:
DR模式下不能跨网段转发数据,如果必须要跨网段进行负载,那么就必须使用LVS/TUN模式。
称为隧道模型RealServer服务器与前端的Director可以在不同的网络中,此种模型也不支持端口映射,RealServer只能使用哪些支持IP隧道的操作系统,前端的Director只处理客户端的请求,然后将请求转发给RealServer,由后台的RealServer直接响应客户端,不再经过Director,RIP一定不能是私有IP,在DR、TUN模式中,数据包是直接返回给用户的,所以,在Director Server上以及集群的每个节点上都需要设置这个地址。此IP在Real Server上一般绑定在回环地址上,例如lo:0,同样,在Director Server上,虚拟IP绑定在真实的网络接口设备上,例如eth0:0。
准备四台服务器或虚拟机:
Web Nginx:10.16.8.8/10.16.8.9 Keepalived:10.16.8.10/10.16.8.11 Keepalived VIP:10.16.8.100/10.16.8.101 OS:CentOS Linux release 7.4.1708 (Core)
先决条件:
安装keepalived。
时间同步。
设置SELinux和防火墙。
互相之间/etc/hosts文件添加对方主机名(可选)。
确认网络接口支持多播(组播)新网卡默认支持。
以上部署请参阅:《keepalived 安装及配置文件讲解》。
$ vim /usr/local/keepalived/etc/keepalived/keepalived.conf global_defs { notification_email { root@localhost } notification_email_from ka@localhost smtp_server 127.0.0.1 smtp_connect_timeout 60 vrrp_mcast_group4 224.0.0.111 } vrrp_instance VI_1 { state MASTER interface eth1 virtual_router_id 191 priority 100 advert_int 1 authentication { auth_type PASS auth_pass renwole0 } virtual_ipaddress { 10.16.8.100 } notify_master "/usr/local/keepalived/etc/keepalived/notify.sh master" notify_backup "/usr/local/keepalived/etc/keepalived/notify.sh backup" notify_fault "/usr/local/keepalived/etc/keepalived/notify.sh fault" } vrrp_instance VI_2 { state BACKUP interface eth1 virtual_router_id 192 priority 95 advert_int 1 authentication { auth_type PASS auth_pass renwole1 } virtual_ipaddress { 10.16.8.101 } notify_master "/usr/local/keepalived/etc/keepalived/notify.sh master" notify_backup "/usr/local/keepalived/etc/keepalived/notify.sh backup" notify_fault "/usr/local/keepalived/etc/keepalived/notify.sh fault" }
$ vim /usr/local/keepalived/etc/keepalived/keepalived.conf global_defs { notification_email { root@localhost } notification_email_from ka@localhost smtp_server 127.0.0.1 smtp_connect_timeout 60 vrrp_mcast_group4 224.0.0.111 } vrrp_instance VI_1 { state BACKUP interface eth1 virtual_router_id 191 priority 95 advert_int 1 authentication { auth_type PASS auth_pass renwole0 } virtual_ipaddress { 10.16.8.100 } notify_master "/usr/local/keepalived/etc/keepalived/notify.sh master" notify_backup "/usr/local/keepalived/etc/keepalived/notify.sh backup" notify_fault "/usr/local/keepalived/etc/keepalived/notify.sh fault" } vrrp_instance VI_2 { state MASTER interface eth1 virtual_router_id 192 priority 100 advert_int 1 authentication { auth_type PASS auth_pass renwole1 } virtual_ipaddress { 10.16.8.101 } notify_master "/usr/local/keepalived/etc/keepalived/notify.sh master" notify_backup "/usr/local/keepalived/etc/keepalived/notify.sh backup" notify_fault "/usr/local/keepalived/etc/keepalived/notify.sh fault" }
分别创建此脚本:
$ vim /usr/local/keepalived/etc/keepalived/notify.sh #!/bin/bash # contact='root@localhost' notify() { local mailsubject="$(hostname) to be $1, vip floating" local mailbody="$(date +'%F %T'): vrrp transition, $(hostname) changed to be $1" echo "$mailbody" | mail -s "$mailsubject" $contact } case $1 in master) notify master ;; backup) notify backup ;; fault) notify fault ;; *) echo "Usage: $(basename $0) {master|backup|fault}" exit 1 ;; esac
$ systemctl start keepalived $ systemctl enable keepalived
我们还可以在任意一台keepalived节点,通过tcpdump命令查看组播心跳状态,例如:
$ tcpdump -nn -i eth1 host 224.0.0.111 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth1, link-type EN10MB (Ethernet), capture size 262144 bytes 00:32:31.714987 IP 10.16.8.10 > 224.0.0.111: VRRPv2, Advertisement, vrid 191, prio 100, authtype simple, intvl 1s, length 20 00:32:31.715739 IP 10.16.8.11 > 224.0.0.111: VRRPv2, Advertisement, vrid 192, prio 100, authtype simple, intvl 1s, length 20 00:32:32.716150 IP 10.16.8.10 > 224.0.0.111: VRRPv2, Advertisement, vrid 191, prio 100, authtype simple, intvl 1s, length 20 00:32:32.716292 IP 10.16.8.11 > 224.0.0.111: VRRPv2, Advertisement, vrid 192, prio 100, authtype simple, intvl 1s, length 20 00:32:33.717327 IP 10.16.8.10 > 224.0.0.111: VRRPv2, Advertisement, vrid 191, prio 100, authtype simple, intvl 1s, length 20 00:32:33.721361 IP 10.16.8.11 > 224.0.0.111: VRRPv2, Advertisement, vrid 192, prio 100, authtype simple, intvl 1s, length 20
如果提示报错:-bash: tcpdump: command not found.
安装tcpdump即可:
$ yum install tcpdump -y
分别安装lvs。CentOS7已经集成了LVS的核心,所以只需要安装LVS的管理工具就可以了:
$ yum -y install ipvsadm 分别停止ka67/ka68的keepalived服务: $ systemctl stop keepalived 分别在ka67/ka68配置文件最后添加Virtual Server配置: $ vim /usr/local/keepalived/etc/keepalived/keepalived.conf virtual_server 10.16.8.100 80 { delay_loop 3 lb_algo rr lb_kind DR protocol TCP # sorry_server 127.0.0.1 80 real_server 10.16.8.8 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 1 nb_get_retry 3 delay_before_retry 1 } } real_server 10.16.8.9 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 1 nb_get_retry 3 delay_before_retry 1 } } } virtual_server 10.16.8.101 80 { delay_loop 3 lb_algo rr lb_kind DR protocol TCP # sorry_server 127.0.0.1 80 real_server 10.16.8.8 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 1 nb_get_retry 3 delay_before_retry 1 } } real_server 10.16.8.9 80 { weight 1 HTTP_GET { url { path / status_code 200 } connect_timeout 1 nb_get_retry 3 delay_before_retry 1 } } }
分别在Web服务器安装Apache Httpd或Nginx作为Web服务,这里安装Nginx。
关于Nginx请参阅:《Centos 7 源码编译安装 Nginx》。
或通过以下方式安装Nginx,简单快速:
$ yum install epel-release -y $ yum install nginx -y
测试环境为区分机器的不同,故将显示页面设置成服务器IP地址,但在生产环境中获取的内容是一致的。
分别在web8/web9执行如下命令:
$ echo "Server 10.16.8.8" > /usr/share/nginx/html/index.html $ echo "Server 10.16.8.9" > /usr/share/nginx/html/index.html
测试是否访问正常:
$ curl http://127.0.0.1 Server 10.16.8.8
由于该脚本部分命令,在Centos7 最小化安装中没有,所以请先安装网络工具包:
$ yum install net-tools -y 分别在web服务器上添加rs.sh脚本: $ vim /tmp/rs.sh #!/bin/bash vip1=10.16.8.100 vip2=10.16.8.101 dev1=lo:1 dev2=lo:2 case $1 in start) echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce ifconfig $dev1 $vip1 netmask 255.255.255.255 broadcast $vip1 up ifconfig $dev2 $vip2 netmask 255.255.255.255 broadcast $vip2 up echo "VS Server is Ready!" ;; stop) ifconfig $dev down echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/lo/arp_ignore echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce echo 0 > /proc/sys/net/ipv4/conf/lo/arp_announce echo "VS Server is Cancel!" ;; *) echo "Usage `basename $0` start|stop" exit 1 ;; esac
再分别启动该脚本:
$ /tmp/rs.sh start 如果需要停止,请执行如下命令: $ /tmp/rs.sh stop
在另一台服务器测试是否能够访问
[root@localhost ~]# for i in `seq 5`; do > curl 10.16.8.100 > curl 10.16.8.101 > done Server 10.16.8.9 Server 10.16.8.8 Server 10.16.8.8 Server 10.16.8.9 Server 10.16.8.9 Server 10.16.8.8 Server 10.16.8.8 Server 10.16.8.9 Server 10.16.8.9 Server 10.16.8.8
根据测试结果判断,已经实现了Keepalived+LVS-DR+Nginx高可用故障切换模式。
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