使用keepalived实现nginx的高可用性

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一，简介

  nginx是一款轻量级的web服务器和反向代理服务器，它拥有较强的并发能力，较为简单灵活的配置，以及超强的性能。nginx越来越受到人们的关注，国内许多站点都采用nginx作为其web服务器或者反向代理。

  keepalived是linux中使用vrrp协议实现高可用功能的一个软件，vrrp可以将两台或者多台路由设备虚拟成一台设备，并提供vip供外网访问，内部通过相应算法选举出MASTER，将vip配置在MASTER上，向外提供相应服务，当MASTER宕机时，BACKUP在一定时间内接收不到MASTER传递过来的信息时，此时，选举会再次发生，BACKUP节点就会取代MASTER节点，成为新的MASTER，并继续向外提供服务，这就实现了服务的高可用性。
二，实验环境
两台linux主机，系统版本为redhat5.8 32位
node1的ip地址为： 192.168.1.85
node2的ip地址为： 192.168.1.86
vip为： 192.168.1.90
keepalived软件版本 keepalived-1.2.7.tar.gz 下载地址：http://www.keepalived.org/download.html

nginx软件版本为：nginx-1.4.7.tar.gz  下载地址为 http://nginx.org/

三，实验过程
1，解压并安装相应软件
keepalived:

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tar xf keepalived-1.2.7.tar.gz cd keepalived-1.2.7 ./configure make make install

(1)拷贝相应文件到相应目录中

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cp /usr/local/sbin/keepalived /usr/sbin/ cp /usr/local/etc/rc.d/init.d/keepalived /etc/init.d/ cp /usr/local/etc/sysconfig/keepalived /etc/sysconfig/ cp /usr/local/etc/keepalived/ /etc/ -r

(2)编辑keepalived.conf配置文件

1	cp /etc/keepalived/keepalived.conf /etc/keepalived/keepalived.conf.bkup 保存一份配置

编辑如下

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! Configuration File for keepalived global_defs {    notification_email {     root@localhost     #定义收件人    }    notification_email_from keepalived@localhost    #定义发件人    smtp_server 127.0.0.1    smtp_connect_timeout 30    router_id LVS_DEVEL } vrrp_script chk_nginx {     script "killall -0 nginx"     #检测nginx是否在线     interval 1        #检测周期为1秒     weight 2          #如果nginx不在线，则权重降低2 } vrrp_script chk_keepalived_down {    script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"  #测试keepalived的主备切换情况    interval 1    weight 2 } vrrp_instance VI_1 {     state MASTER      #node1为主节点     interface eth0    #监听的接口     virtual_router_id 52    #虚拟路由ID，两端必须一致

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priority 101     #优先级，MASTER端要高于BACKUP端     advert_int 1     #通告周期 1 秒     authentication {         auth_type PASS    #认证方式         auth_pass 1111    #认证秘钥     }     virtual_ipaddress {         192.168.1.90     #vip的设定     }     track_script {      #要执行的检测脚本         chk_nginx         chk_mantaince_down     }

keepalived.conf中还有许多内容，但都是为lvs准备，这里并没有启动lvs功能，所以都删掉了。
node2的配置和node1类似，只不过要把state MASTER改为BACKUP,把优先级调的比MASTER小一些即可。

nginx:
(1)解决依赖关系

1	yum install pcre-devel -y

(2)添加用户和组

1 2	groupadd -r nginx useradd -r -g nginx nginx

(3)解压并编译安装

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tar xf  nginx-1.4.7.tar.gz cd nginx-1.4.7 ./configure   --prefix=/usr   --sbin-path=/usr/sbin/nginx   --conf-path=/etc/nginx/nginx.conf   --error-log-path=/var/log/nginx/error.log   --http-log-path=/var/log/nginx/access.log   --pid-path=/var/run/nginx/nginx.pid    --lock-path=/var/lock/nginx.lock   --user=nginx   --group=nginx   --with-http_ssl_module   --with-http_flv_module   --with-http_stub_status_module   --with-http_gzip_static_module   --http-client-body-temp-path=/var/tmp/nginx/client/   --http-proxy-temp-path=/var/tmp/nginx/proxy/   --http-fastcgi-temp-path=/var/tmp/nginx/fcgi/   --http-uwsgi-temp-path=/var/tmp/nginx/uwsgi   --http-scgi-temp-path=/var/tmp/nginx/scgi   --with-pcre

make && make install
(4)修改下主页后就可以启动服务了

在两个节点上启动keepalived

1	service keepalived start

在node1上查看日志

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tail /var/log/messages Aug 19 19:12:16 localhost Keepalived_vrrp[27587]: VRRP_Script(chk_nginx) succeeded Aug 19 19:12:16 localhost Keepalived_vrrp[27587]: VRRP_Script(chk_mantaince_down) succeeded Aug 19 19:12:17 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Transition to MASTER STATE Aug 19 19:12:18 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Entering MASTER STATE Aug 19 19:12:18 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) setting protocol VIPs. Aug 19 19:12:18 localhost Keepalived_healthcheckers[27586]: Netlink reflector reports IP 192.168.1.90 added Aug 19 19:12:18 localhost avahi-daemon[3327]: Registering new address record for 192.168.1.90 on eth0. Aug 19 19:12:18 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90 Aug 19 19:12:18 localhost Keepalived_vrrp[27587]: Netlink reflector reports IP 192.168.1.90 added Aug 19 19:12:23 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90

可以看到node1被选举为master，vip配置在node1上
使用ip addr 查看

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... 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast qlen 1000     link/ether 00:0c:29:a3:12:75 brd ff:ff:ff:ff:ff:ff     inet 192.168.1.85/24 brd 192.168.1.255 scope global eth0     inet 192.168.1.90/32 scope global eth0

查看node2上日志信息

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Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Registering Kernel netlink reflector Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Registering Kernel netlink command channel Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Registering gratuitous ARP shared channel Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Opening file '/etc/keepalived/keepalived.conf'. Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Configuration is using : 40529 Bytes Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: Using LinkWatch kernel netlink reflector... Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) Entering BACKUP STATE Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP sockpool: [ifindex(2), proto(112), fd(11,12)] Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP_Script(chk_nginx) succeeded Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP_Script(chk_mantaince_down) succeeded

为backup状态

此时打开浏览器访问vip 192.168.1.90 提供页面的是node1

将node1上的nginx服务down掉

1	service nginx stop

再次查看node1 上的日志

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Aug 19 19:18:15 localhost Keepalived_vrrp[27587]: VRRP_Script(chk_nginx) failed Aug 19 19:18:16 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Received higher prio advert Aug 19 19:18:16 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) Entering BACKUP STATE Aug 19 19:18:16 localhost Keepalived_vrrp[27587]: VRRP_Instance(VI_1) removing protocol VIPs. Aug 19 19:18:16 localhost Keepalived_healthcheckers[27586]: Netlink reflector reports IP 192.168.1.90 removed Aug 19 19:18:16 localhost avahi-daemon[3327]: Withdrawing address record for 192.168.1.90 on eth0. Aug 19 19:18:16 localhost Keepalived_vrrp[27587]: Netlink reflector reports IP 192.168.1.90 removed Aug 19 19:18:17 localhost Keepalived_vrrp[27587]: VRRP_Script(chk_nginx) succeeded

此时，node1已经变为backup状态，vip也已经被移除

查看node2的日志信息

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Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP_Script(chk_nginx) succeeded Aug 19 19:12:17 localhost Keepalived_vrrp[16800]: VRRP_Script(chk_mantaince_down) succeeded Aug 19 19:18:16 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) forcing a new MASTER election Aug 19 19:18:17 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) Transition to MASTER STATE Aug 19 19:18:18 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) Entering MASTER STATE Aug 19 19:18:18 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) setting protocol VIPs. Aug 19 19:18:18 localhost Keepalived_vrrp[16800]: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth0 for 192.168.1.90

node2成为master节点，整个切换过程完成。