一、場景需求

二、Keepalived 簡要介紹
Keepalived 是一種高效能的伺服器高可用或熱備解決方案，Keepalived 可以用來防止伺服器單點故障的發生，通過配合 Nginx 可以實現 web 前端服務的高可用。
Keepalived 以 VRRP 協議為實現基礎，用 VRRP 協議來實現高可用性(HA)。VRRP(VirtualRouter
Redundancy Protocol)協議是用於實現路由器冗餘的協議，VRRP 協議將兩臺或多臺路由器裝置虛擬成一個裝置，對外提供虛擬路由器 IP(一個或多個)，而在路由器組內部，如果實際擁有這個對外 IP 的路由器如果工作正常的話就是 MASTER，或者是通過

演算法選舉產生，MASTER 實現針對虛擬路由器 IP 的各種網路功能，
如 ARP 請求，ICMP，以及資料的轉發等；其他裝置不擁有該虛擬 IP，狀態是 BACKUP，除了接收 MASTER 的VRRP 狀態通告資訊外，不執行對外的網路功能。當主機失效時，BACKUP 將接管原先 MASTER 的網路功能。VRRP 協議使用多播資料來傳輸 VRRP 資料，VRRP 資料使用特殊的虛擬源 MAC 地址傳送資料而不是自身網絡卡的 MAC 地址，VRRP 執行時只有 MASTER 路由器定時傳送 VRRP 通告資訊，表示 MASTER 工作正常以及虛擬路由器 IP(組)，BACKUP 只接收 VRRP 資料，不傳送資料，如果一定時間內沒有接收到 MASTER 的通告資訊，各 BACKUP 將宣告自己成為 MASTER，傳送通告資訊，重新進行 MASTER 選舉狀態。

三、方案規劃

 

四、安裝 Nginx

1、安裝編譯 Nginx 所需的依賴包

Connecting to 192.168.1.121:22...
Connection established.
To escape to local shell, press 'Ctrl+Alt+]'.


Last login: Sat Apr 16 17:55:20 2016 from 192.168.1.61
[[email protected] ~]# yum install gcc gcc-c++ make automake autoconf libtool pcre pcre-devel zlib zlib-devel openssl openssl-devel

2、上傳 Nginx(nginx-1.6.2.tar.gz)到 /usr/local/src 目錄

3、編譯安裝 Nginx

[[email protected] ~]# cd /usr/local/src/
[[email protected] src]# ls
keepalived-1.2.18.tar.gz  nginx-1.6.2.tar.gz
[[email protected] src]# tar -zxvf nginx-1.6.2.tar.gz 

[[email protected] src]# cd nginx-1.6.2
[[email protected] nginx-1.6.2]# ./configure --prefix=/usr/local/nginx

[[email protected] nginx-1.6.2]# make && make install

[[email protected] nginx-1.6.2]# vi /usr/local/nginx/conf/nginx.conf

user  root;
worker_processes  1;


#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;
#pid        logs/nginx.pid;


events {
    worker_connections  1024;
}


http {
    include       mime.types;
    default_type  application/octet-stream;


    #log_format  main  '$remote_addr - $remote_user [$time_local] "$request" '
    #                  '$status $body_bytes_sent "$http_referer" '
    #                  '"$http_user_agent" "$http_x_forwarded_for"';


    #access_log  logs/access.log  main;


    sendfile        on;
    #tcp_nopush     on;


    #keepalive_timeout  0;
    keepalive_timeout  65;


    #gzip  on;


    server {
        listen       88;
        server_name  localhost;
        #charset koi8-r;
        #access_log  logs/host.access.log  main;
        location / {
            root   html;
            index  index.html index.htm;
        }
        #error_page  404              /404.html;
        # redirect server error pages to the static page /50x.html
        error_page   500 502 503 504  /50x.html;
        location = /50x.html {
            root   html;
        }
    }
}

修改 Nginx 歡迎首頁內容（用於後面測試，用於區分兩個節點的 Nginx）：

vi /usr/local/nginx/html/index.html 

192.168.1.121 中的標題加 1

Welcome to nginx! 1

192.168.1.122 中的標題加 2 

Welcome to nginx! 2

5、系統防火牆開啟對應的埠 88

vi /etc/sysconfig/iptables

 -A INPUT -m state --state NEW -m tcp -p tcp --dport 88 -j ACCEPT

service iptables restart

6、測試 Nginx 是否安裝成功

/usr/local/nginx/sbin/nginx -t

nginx: the configuration file /usr/local/nginx/conf/nginx.conf syntax is ok
nginx: configuration file /usr/local/nginx/conf/nginx.conf test is successful

7、啟動 Nginx

/usr/local/nginx/sbin/nginx 

重啟

/usr/local/nginx/sbin/nginx -s reload

8、設定 Nginx 開機啟動

vi /etc/rc.local 

加入

/usr/local/nginx/sbin/nginx

分別訪問兩個nginx

nginx1

2.nginx2

 1、上傳或下載 keepalived（keepalived-1.2.18.tar.gz）到 /usr/local/src 目錄

2、解壓安裝

 cd /usr/local/src

 tar -zxvf keepalived-1.2.18.tar.gz

cd keepalived-1.2.18

 ./configure --prefix=/usr/local/keepalived

 make && make install

3、將 keepalived 安裝成 Linux 系統服務：

因為沒有使用 keepalived 的預設路徑安裝（預設是/usr/local）,安裝完成之後，需要做一些工作

複製預設配置檔案到預設路徑

mkdir /etc/keepalived

 cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/

複製 keepalived 服務指令碼到預設的地址

 cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/

 cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/

 ln -s /usr/local/sbin/keepalived /usr/sbin/

ln -s /usr/local/keepalived/sbin/keepalived /sbin/

設定 keepalived 服務開機啟動

chkconfig keepalived on

4、修改 Keepalived 配置檔案

 注意，如果linux用的網絡卡是eth0,interface就要寫成eth1，用的是eth1就要寫成eth1

(1) MASTER 節點配置檔案（192.168.1.121）

vi /etc/keepalived/keepalived.conf

! Configuration File for keepalived


global_defs {
   router_id edu-proxy-01
}


vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh"
    interval 2
    weight -20
}


vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    mcast_src_ip 192.168.1.121
    priority 100
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }


    track_script {
        chk_nginx
    }


    virtual_ipaddress {
        192.168.1.120
    }

BACKUP節點配置 （192.168.1.122）

! Configuration File for keepalived


global_defs {
   router_id edu-proxy-02
}


vrrp_script chk_nginx {
    script "/etc/keepalived/nginx_check.sh"
    interval 2
    weight -20
}


vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    mcast_src_ip 192.168.1.122
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }


    track_script {
        chk_nginx
    }


    virtual_ipaddress {
        192.168.1.120
    }
}

5.編寫Nginx狀態檢測指令碼/etc/keepalived/nginx_check.sh(keepalived.conf中配置)

指令碼要求:如果nginx停止執行，嘗試啟動，如果無法啟動則殺死本機的keepalived程序，keepaied將虛擬ip繫結到BACKUP機器上，內容如下

#!/bin/bash
A=`ps -C nginx –no-header |wc -l`
if [ $A -eq 0 ];then
    /usr/local/nginx/sbin/nginx
    sleep 2
    if [ `ps -C nginx --no-header |wc -l` -eq 0 ];then
        killall keepalived
    fi

fi

儲存後給指令碼授鄧許可權

chmod -x /etc/keepalived/nginx_check.sh 

6.啟動keepalived

serivce keepalived start

我們在cmd中檢視arp

在edu-proxy-01

[[email protected] keepalived]# ip add

這裡我們訪問192.168.1.120:88

7.Keepalived+nginx的高可用測試

(1)關閉192.168.1.121的Nginx,Keepalived會將它重新啟動

[[email protected] keepalived]# /usr/local/nginx/sbin/nginx -s stop

(2)關閉192.168.1.121中的Keepalived,VIP會切換到192.168.1.122中

[[email protected] keepalived]# service keepalived stop

[email protected]-02 keepalived]# ip add

檢視虛擬ip

說明此時VIP已經漂移到主機192.168.1.122上了

再能過VIP來訪問Nginx叢集，訪問到的也是192.168.1.122

(3)重新啟動192.168.1.121中的Keepalived,VIP又會切回到192.168.1.121中來

[[email protected] keepalived]# service keepalived start

檢視虛擬機器IP

ip add

Keepalived啟動後，網路介面上又會創建出VIP192.168.1.120

Keepalived服務管理命令:

停止: service keepalived stop

啟動: service keepalived start

重啟: service keepalived restart

檢視狀態: service keepalived status

其他參考資料:

keepalived之vrrp_script總結:http://my.oschina.net/hncscwc/blog/158746

keepalived雙機熱備實現故障時傳送郵件通知:http://www.2cto.com/os/201407/317795.html