Nginx keepalive 負載均衡

兩台相同配置的web

用途ip

master

192.168.1.100

backup

192.1681.101

兩台接入伺服器分別安裝nginx和keepalived:

準備依賴包：

安裝nginx

安裝keepalive

tar zxvf keepalived-1.2.7

.tar.gz

cd keepalived-1.2.7

./configure

make

make install

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

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

加入啟動服務

echo "
/usr/local/nginx/sbin/nginx
" >> /etc/rc.local
echo 
"/etc/init.d/keepalived start
" >> /etc/rc.local

3.1配置nginx

兩台接入伺服器的nginx的配置完全一樣,主要是配置/usr/local/nginx/conf/nginx.conf的http。其中多網域名稱指向是通過虛擬主機（配置http下面的server）實現；同一網域名稱的不同虛擬目錄通過每個server下面的不同location實現；到後端的伺服器在http下面配置upstream,然後在server或location中通過proxypass引用。要實現前面規劃的接入方式，http的配置如下：

驗證方法：

首先用ip訪問前表中各個應用伺服器的url

再用網域名稱和路徑訪問前表中各個應用系統的網域名稱/虛擬路徑

3.2配置keepalived

master:

! configuration file for

keepalived

global_defs

vrrp_instance vi_1

virtual_ipaddress

}backup:

! configuration file for

keepalived

global_defs

vrrp_instance vi_1

virtual_ipaddress

}

驗證：先後在主、從伺服器上啟動keepalived: /etc/init.d/keepalived start

在主伺服器上檢視是否已經繫結了虛擬ip： ip addr

停止主伺服器上的keepalived: /etc/init.d/keepalived stop 然後在從伺服器上檢視是否已經繫結了虛擬ip：

啟動主伺服器上的keepalived，看看主伺服器能否重新接管虛擬ip

3.3讓keepalived監控nginx的狀態

經過前面的配置，如果主伺服器的keepalived停止服務，從伺服器會自動接管vip對外服務；一旦主伺服器的keepalived恢復，會重新接管vip。但這並不是我們需要的，我們需要的是當nginx停止服務的時候能夠自動切換。

keepalived支援配置監控指令碼，我們可以通過指令碼監控nginx的狀態，如果狀態不正常則進行一系列的操作，最終仍不能恢復nginx則殺掉keepalived，使得從伺服器能夠接管服務。

如何監控nginx的狀態

最簡單的做法是監控nginx程序，更靠譜的做法是檢查nginx埠，最靠譜的做法是檢查多個url能否獲取到頁面。

如何嘗試恢復服務

如果發現nginx不正常，重啟之。等待3秒再次校驗，仍然失敗則不再嘗試。

根據上述策略很容易寫出監控指令碼。這裡使用nmap檢查nginx埠來判斷nginx的狀態，記得要首先安裝nmap。監控指令碼如下:

#!/bin/bash
# check nginx server status
nginx=/usr/local/nginx/sbin/nginx
port=8080
nmap localhost -p $port | grep "
$port/tcp open
"#echo $?
if [ $? -ne 0
];then
$nginx -s stop
$nginx
sleep 
3nmap localhost -p $port | grep "
$port/tcp open
"[ $? -ne 0 ] && /etc/init.d/keepalived stop
fi

不要忘了設定指令碼的執行許可權，否則不起作用。

假設上述指令碼放在/opt/chk_nginx.sh，則keepalived.conf中增加如下配置：

主keepalived

例子：! configuration file for

更進一步，為了避免啟動keepalived之前沒有啟動nginx , 可以在/etc/init.d/keepalived的start中首先啟動nginx:

start() 
retval=$?echo
[ $retval -eq 0 ] && touch /var/lock/subsys/$prog
}

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