nginx+keepalived雙機熱備+負載均衡

一、原理/需求

結合keepalived 對前端nginx實現HA；
nginx進程基於Master+Slave(worker)多進程模型，自身具備很是穩定的子進程管理功能。在Master進程分配模式下，Master進程永遠不進行業務處理，只是進行任務分發，從而達到Master進程的存活高可靠性，Slave(worker)進程全部的業務信號都由主進程發出，Slave(worker)進程全部的超時任務都會被Master停止，屬於非阻塞式任務模型。
Keepalived是Linux下面實現VRRP備份路由的高可靠性運行件。基於Keepalived設計的服務模式可以真正作到主服務器和備份服務器故障時IP瞬間無縫交接。兩者結合，能夠構架出比較穩定的軟件lb方案。

二、環境說明
192.168.2.4        keepalived nginx
192.168.2.5        keepalived nginx
虛擬IP (VIP)：192.168.2.6

三、安裝keepalived和nginx

yum -y install openssl-devel

yum -y install libnl libnl-devel

yum install -y libnfnetlink-devel

[root@master keepalived-1.3.9]# ./configure --prefix=/usr/local/keepalived

[root@master keepalived-1.3.9]# make && make install

[root@master ~]# mkdir /etc/keepalived

[root@master ~]# cp /usr/local/keepalived/etc/keepalived/keepalived.conf /etc/keepalived/

[root@master ~]# /usr/local/keepalived/sbin/keepalived -D

四、配置MASTER  keepalived
vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
#標識本節點的名稱
   router_id master	
}

vrrp_script chk_nginx {  
	script "/etc/keepalived/nginx_check.sh"
	#每2秒檢測一次nginx的運行狀態
	interval 2
	#失敗一次，將本身的優先級調整爲-20
	weight	-20
} 

vrrp_instance VI_1 {
	#狀態，主節點爲MASTER
	state MASTER
	#綁定VIP的網絡接口
	interface ens33
	#虛擬路由的ID號，兩個節點設置必須同樣
	virtual_router_id 51
	#節點優先級，值範圍0~254，MASTER>BACKUP
	priority 100
	#組播信息發送時間間隔，兩個節點必須設置同樣，默認爲1秒
	advert_int 1
	#設置驗證信息，兩個節點必須一致
	authentication {
	        auth_type PASS
        	auth_pass 1111
    	}
	#虛擬IP，兩個節點設置必須一致，能夠設置多個
	virtual_ipaddress {
        	192.168.1.106
    	}
    	#nginx存活狀態檢測腳本
	track_script {
		chk_nginx
	}
}

五、配置BACKUP  keepalived
vim /etc/keepalived/keepalived.conf

! Configuration File for keepalived

global_defs {
   router_id backup
}

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

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 51
    priority 99
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.1.106
    }
    track_script {
        chk_nginx
    }
}

Tips：
state   參數值：主的是MASTER、備用的是BACKUP
priority 參數值： MASTER > BACKUP
virtual_router_id： 參數值要同樣

調用的腳本nginx_check.sh

#!/bin/bash  
A=`ps -C nginx -no-header |wc -l`  
if [ $A -eq 1 ];then 
        pkill keepalived  
fi

測試：

兩臺測試機4\5均啓動keepalived和nginx
service keepalived restart
service keepalived nginx

驗證nginx啓動正常：
訪問 master：http://192.168.2.4:80/
訪問 backup: http://192.168.2.5:80/

查看keepalived的日誌信息：

4\5均打開日誌信息方便查看keepalived動態：
tail -f /var/log/messages

瀏覽器打開虛擬ip訪問：http://192.168.2.6:80/ ，此時顯示IP爲192.168.2.4

服務器層的雙機熱備（好比服務器宕機、keepalived宕了）測試：

kill 192.168.2.4（master) 的keepalived進程
killall keepalived

4的日誌信息以下：

Jun 11 18:03:10 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6  
Jun 11 18:03:15 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6  
Jun 11 19:30:44 localhost Keepalived: Terminating on signal  
Jun 11 19:30:44 localhost Keepalived: Stopping Keepalived v1.2.2 (06/10,2014)  
Jun 11 19:30:44 localhost Keepalived_vrrp: Terminating VRRP child process on signal  
Jun 11 19:30:44 localhost Keepalived_healthcheckers: Terminating Healthchecker child process on signal

5的日誌信息以下：

Jun 11 19:30:50 localhost Keepalived_vrrp: VRRP_Instance(VI_1) setting protocol VIPs.  
Jun 11 19:30:50 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6  
Jun 11 19:30:50 localhost Keepalived_healthcheckers: Netlink reflector reports IP 192.168.2.6 added  
Jun 11 19:30:55 localhost Keepalived_vrrp: VRRP_Instance(VI_1) Sending gratuitous ARPs on eth1 for 192.168.2.6

刷新http://192.168.2.6:80/ ， 此時顯示IP爲192.168.2.5。 再次啓動192.168.2.4的keepalived進程，192.168.2.4會自動接管成爲master，192.168.2.5自動轉爲backup，從測試結果看，備機能成功接管，已經實現了熱備。