Keepalived雙機熱備

這裏我們僅僅只利用Keepalive做雙機熱備，也就是保證服務器的高可用性，其他的不用管。可能您會說這樣在實際應用中很少會這樣用，這您可就錯了，Keepalived僅僅做雙機熱備的情況還是有的，我就碰到過幾次這樣的案例，下面就我碰到的幾個案例做個小結

一，Keepalived雙機熱備的應用場景

1，網站流量不高，壓力不大，但是對服務器的可靠性要求極其高，例如實時在線OA系統，政府部門網站系統，醫院實時報醫系統，公安局在線報案系統，股市後臺網站系統等等，他們的壓力不是很大，但是對可靠性要求是非常高的

2，有錢沒地方花的，典型的政府企業，公辦學校等等

二，Keepalived雙機熱備的特性以及優缺點

特性：
1，至少需要兩臺服務器，其中一臺爲master始終提供服務，另外一臺作爲backup始終處於空閒狀態，只有在主服務器掛掉的時候他就來幫忙了，這是典型的雙擊熱備

2，能根據需求判斷服務是否可用，在不可用的時候要即使切換
優缺點：

優點：數據同步非常簡單，不像負載均衡對數據一致性要求非常高，實現起來相對複雜維護也頗爲不便，雙機熱備用rsync就可以實現了操作和維護非常簡單

缺點：服務器有點浪費，始終有一臺處於空閒狀態

三，Keepalived雙機熱備的配置
首先畫個雙機熱備拓撲圖吧：

這裏我只寫最終實現的配置，至於Keepalived的理論知識請參考《Keepalived原理與實戰精講》

1，本例通過Keepalived來實現兩臺LNMP(也就是linux+nginx+mysql+php)架構服務器的雙機熱備

LNMP的配置請參考：《Lnmp配置精講第一版》

2，Keepalived配置雙機安裝配置

1》Keepalived安裝

keepalived官方地址：http://www.keepalived.org/download.html，大家可以到這裏下載最新版本的keepalived

操作系統：centos 5.5 32bit
系統安裝：最小化安裝，也就是去掉所有組件
環境配置：安裝make 和 gcc openssl openssl-devel等等

yum -y install gcc make openssl openssl-devel wget kernel-devel
mkdir -p /usr/local/src/hasoft
cd /usr/local/src/hasoft
wget http://www.keepalived.org/software/keepalived-1.2.2.tar.gz
tar -zxvf keepalived-1.2.2.tar.gz
cd keepalived-1.2.2
./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/

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預編譯後出現：

Keepalived configuration
------------------------
Keepalived version : 1.2.2
Compiler : gcc
Compiler flags : -g -O2 -DETHERTYPE_IPV6=0x86dd
Extra Lib : -lpopt -lssl -lcrypto
Use IPVS Framework : Yes
IPVS sync daemon support : Yes
IPVS use libnl : No
Use VRRP Framework : Yes
Use Debug flags : No

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make && make install

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這裏注意哦，我上面是指通用的安裝方法，如果你沒有用到LVS可以把lvs去掉即
./configure --prefix=/usr/local/keepalived --with-kernel-dir=/usr/src/kernels/2.6.18-238.19.1.el5-i686/ --disable-lvs-syncd --disable-lvs

但這個沒有影響，就按照我的來配置吧，不過如果你要是集成了LVS，那麼就不可加這兩個參數了哦

整理管理文件：
cp /usr/local/keepalived/sbin/keepalived /usr/sbin/
cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig/
cp /usr/local/keepalived/etc/rc.d/init.d/keepalived /etc/init.d/

建立配置文件目錄(注意：keepalived的配置文件默認在/etc/keepalived/目錄)
mkdir -p /etc/etc/keepalived/

兩臺服務器(兩個節點)都這樣安裝即可

2》配置

節點A配置如下：
vi /etc/keepalived/keepalived.conf

global_defs
{
notification_email
{
[email protected]
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
stmp_connect_timeout 30
router_id lnmp_node1
}
vrrp_instance lnmp {
state MASTER
interface eth0
virtual_router_id 100
priority 200
advert_int 5
track_interface {
eth0
eth1
}
authentication {
auth_type PASS
auth_pass 123456
}
virtual_ipaddress {
192.168.17.200
}
}

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節點B配置如下：
vi /etc/keepalived/keepalived.conf

global_defs
{
notification_email
{
[email protected]
[email protected]
}
notification_email_from [email protected]
smtp_server 127.0.0.1
stmp_connect_timeout 30
router_id lnmp_node1
}
vrrp_instance lnmp {
state MASTER
interface eth0
virtual_router_id 100
priority 150
advert_int 5
track_interface {
eth0
eth1
}
authentication {
auth_type PASS
auth_pass 123456
}
virtual_ipaddress {
192.168.17.200
}
}

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四，啓動調試
在節點A上啓動
/usr/local/keepalived/sbin/keepalived

啓動日誌：
Sep  8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink reflector
Sep  8 18:26:02 centosa Keepalived_vrrp: Registering Kernel netlink command channel
Sep  8 18:26:02 centosa Keepalived_vrrp: Registering gratutious ARP shared channel
Sep  8 18:26:02 centosa Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Sep  8 18:26:02 centosa Keepalived_vrrp: Configuration is using : 36076 Bytes
Sep  8 18:26:02 centosa Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Sep  8 18:26:02 centosa Keepalived: Starting VRRP child process, pid=5606
Sep  8 18:26:07 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATE
Sep  8 18:26:12 centosa Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATE
Sep  8 18:26:12 centosa avahi-daemon[2528]: Registering new address record for 192.168.17.200 on eth0.

在節點B上啓動
/usr/local/keepalived/sbin/keepalived

開機自動啓動
echo /usr/local/keepalived/sbin/keepalived >> /etc/rc.local

啓動日誌：
Sep  8 18:30:02 centosb Keepalived: Starting Keepalived v1.2.2 (09/08,2011)
Sep  8 18:30:02 centosb Keepalived: Starting Healthcheck child process, pid=5837
Sep  8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink reflector
Sep  8 18:30:02 centosb Keepalived_vrrp: Registering Kernel netlink command channel
Sep  8 18:30:02 centosb Keepalived_vrrp: Registering gratutious ARP shared channel
Sep  8 18:30:02 centosb Keepalived: Starting VRRP child process, pid=5839
Sep  8 18:30:02 centosb kernel: IPVS: Registered protocols (TCP, UDP, AH, ESP)
Sep  8 18:30:02 centosb kernel: IPVS: Connection hash table configured (size=4096, memory=32Kbytes)
Sep  8 18:30:02 centosb kernel: IPVS: ipvs loaded.
Sep  8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink reflector
Sep  8 18:30:02 centosb Keepalived_healthcheckers: Registering Kernel netlink command channel
Sep  8 18:30:02 centosb Keepalived_healthcheckers: Opening file '/etc/keepalived/keepalived.conf'.
Sep  8 18:30:02 centosb Keepalived_vrrp: Opening file '/etc/keepalived/keepalived.conf'.
Sep  8 18:30:02 centosb Keepalived_vrrp: Configuration is using : 36252 Bytes
Sep  8 18:30:02 centosb Keepalived_vrrp: Using LinkWatch kernel netlink reflector...
Sep  8 18:30:02 centosb Keepalived_healthcheckers: Configuration is using : 6271 Bytes
Sep  8 18:30:02 centosb Keepalived_healthcheckers: Using LinkWatch kernel netlink reflector...
Sep  8 18:30:02 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATE

從日誌可以看出，啓動都沒有問題，並且安裝我給的優先級完成了競選，各自成就了各自的狀態

關閉節點A的網卡測試切換是否正常
ifdown eth0

觀察節點B的日誌：
Sep  8 18:32:55 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Transition to MASTER STATE
Sep  8 18:33:00 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering MASTER STATE
Sep  8 18:33:00 centosb avahi-daemon[2531]: Registering new address record for 192.168.17.200 on eth0.

啓動節點A的網卡測試切換是否正常
ifup eth0
觀察節點B的日誌：
Sep  8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Received higher prio advert
Sep  8 18:33:31 centosb Keepalived_vrrp: VRRP_Instance(lnmp) Entering BACKUP STATE
Sep  8 18:33:31 centosb avahi-daemon[2531]: Withdrawing address record for 192.168.17.200 on eth0.

Received higher prio advert：表示接收到更高優先級的公告(advert公告的意思)
Withdrawing：撤回的意思，可以看出切換過程一目瞭然

OK，到這裏我們的安裝部分完成，下面我們來看看如何監控服務吧，我們這裏僅僅是監控了網絡故障和keepalived本身進程，在網絡或者 keepalived進程出現問題的時候會切換，但是我的節點A裏面還有很多服務呢，例如nginx，PHP，mysql進程出問題或高負載的時候相應過慢怎麼辦，怎麼切換的呢，這時就要用到腳本了，下面我們來看看keepalived是如何控制腳本來實現對服務器的監控和切換的

寫個腳本來實時監控三個服務，若有一個出現問題遍切換mkdir /root/shell/
cd /root/shell
vi keepcheck.sh

#!/bin/bash
while :
do
mysqlcheck=`/usr/local/lnmp/mysql/bin/mysqladmin -uroot ping 2>&1`
mysqlcode=`echo $?`
phpcheck=`ps -C php-fpm --no-header | wc -l`
nginxcheck=`ps -C nginx --no-header | wc -l`
keepalivedcheck=`ps -C keepalived --no-header | wc -l`
if [ $nginxcheck -eq 0 ]|| [ $phpcheck -eq 0 ]||[ $mysqlcode -ne 0 ];then
if [ $keepalivedcheck -ne 0 ];then
killall -TERM keepalived
else
echo "keepalived is stoped"
fi
else
if [ $keepalivedcheck -eq 0 ];then
/etc/init.d/keepalived start
else
echo "keepalived is running"
fi
fi
sleep 5
done

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注意，用/etc/init.d/keepalived start如果起不來，可以用/usr/local/keepalived/sbin/keepalived二進制文件直接執行啓動即可
啓動腳本：

chmod +x /root/shell/keepcheck.sh
nohup sh /root/shell/keepcheck.sh &

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節點B也用這個腳本

寫入/etc/rc.local開機自動啓動

echo "nohup sh /root/shell/keepcheck.sh &" >> /etc/rc.loal

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可以測試了

本文就寫完了，這個可以用於生產環境，本人環境就這樣配置的，但不同業務有不同環境，一定要按需調整，不要盲目盲從！

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