前言

在這個高度資訊化的IT時代，企業的生產系統、業務運營、銷售和支援，以及日常管理等環節越來越依賴於計算機資訊和服務，使得對高可用（HA）技術的應用需求大量上升，以便提供持續的、不間斷的計算機系統或網路服務。
使用Keepalived實現雙機熱備，包括針對IP地址的故障切換，以及在LVS高可用群集中的熱備應用。

一、Keepalived 雙機熱備基礎

1.1、Keepalived 概述及安裝

1.1.1、Keepalived 的熱備方式

Keepalived採用VRRP熱備份協議實現Linux伺服器的多機熱備功能

VRRP，虛擬路由冗餘協議，是針對路由器的一種備份解決方案

由多臺路由器組成一個熱備組，通過共用的虛擬IP地址對外提供服務

每個熱備組內同一時刻只有一臺主路由器提供服務，其他路由器處於冗餘狀態

若當前線上的路由器失效，則其他路由器會根據設定的優先順序自動接替虛擬IP地址，繼續提供服務

1.1.2、Keepalived 的安裝與服務控制

在LVS群集環境中應用時，也需用到 lipvsadm管理工具
YUM安裝 Keepalived
啟用 Keepalived服務

[root@localhost ~]# yum -y install keepalived ipvsadm

1.2、使用Keepalived 實現雙機熱備

Keepalived可實現多機熱備，每個熱備組可有多臺伺服器，最常用的就是雙機熱備

雙機熱備的故障切換是由虛擬IP地址的漂移來實現，適用於各種應用伺服器

本次部署將實現基於web服務的雙機熱備

1.2.1、主伺服器的配置

Keepalievd配置目錄位於/etc/keepalievd/
keepalievd.conf是主配置檔案

[root@localhost ~]# cd /etc/keepalived/
[root@localhost keepalived]# cp keepalived.conf keepalived.conf.bak
[root@localhost keepalived]# vi keepalived.conf
global_defs{…}區段指定全域性引數
vrrp_instance例項名稱{…}區段指定VRRP熱備引數
註釋文字以“！”符號開頭
目錄samples/,提供了許多配置樣例作為參考
常用配置選項
router_id HA_TEST_R1: 本路由器（伺服器）的名稱
vrrp_instance VI_1：定義VRRP熱備例項
state MASTER：熱備狀態，MASTER表示主伺服器
interface ens33：承載VIP地址的物理介面
virtual_router_id 1：虛擬路由器的ID號，每個熱備組保持一致
priority 100：優先順序，數值越大優先順序越高
advert_int 1：通告間隔秒數（心跳頻率）
auth_type PASS：認證型別
auth_pass 123456：密碼字串
virtual_ipaddress{vip}：指定漂移地址（VIP），可以有多個，多個漂移地址以逗號分隔

確認配置沒有問題，啟動Keepalived服務，通過ip命令可以檢視

[root@localhost keepalived]# systemctl start keepalived                  ####啟動keepalived
[root@localhost keepalived]# ip addr show dev ens33                      ####檢視主控制IP地址和漂移地址

1.2.2、備用伺服器的配置

Keepalived備份伺服器的配置與master的配置有三個選項不同
router_id:設為自由名稱
state：設為BACKUP
priority：值低於主伺服器
其他選項與master相同

1.2.3、測試雙機熱備功能

測試雙機熱備的效果
主、備機均啟用Web服務，內容相同
先後禁用、啟用主伺服器的網路卡，執行以下測試

測試1：使用ping檢測19216810.72的連通性
測試2：訪問htt:/192168.10.72，確認可用性及內容變化
測試3：檢視日誌檔案/var/log/messages中的變化

二、LVS+Keepalived 高可用群集 實戰部署

2.1、實驗環境

VMware 5臺伺服器
IP地址規劃：
漂移地址（VIP）：192.168.100.100
主排程器：192.168.100.21
輔排程器：192.168.100.20
WEB伺服器1:192.168.100.22
WEB伺服器2:192.168.100.23
儲存伺服器：192.168.100.24

2.2、配置主排程器

2.2.1、調整/proc 響應引數

[

root@localhost network-scripts]# vi /etc/sysctl.conf 
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0
[root@localhost network-scripts]# sysctl -p
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0 

2.2.2、調整keepalived 引數

[root@localhost ~]# yum -y install keepalived ipvsadm
[root@localhost ~]# cd /etc/keepalived/
[root@localhost keepalived]# cp keepalived.conf keepalived.conf.bak
[root@localhost keepalived]# vi keepalived.conf
global_defs {
   router_id HA_TEST_R1
}
vrrp_instance VI_1 {
   state MASTER
   interface ens33
   virtual_router_id 1
   priority 100
   advert_int 1
   authentication {
      auth_type PASS
      auth_pass 123456
   }
   virtual_ipaddress {
      192.168.100.100
   }
}

virtual_server 192.168.100.100 80 {
    delay_loop 15
    lb_algo rr
    lb_kind DR
    persistence 60
    protocol TCP

    real_server 192.168.100.22 80 {
        weight 1
        TCP_CHECK {
	    connect_port 80
	    connect_timeout 3
	    nb_get_retry 3
	    delay_before_retry 4
	}
    }
    real_server 192.168.100.23 80 {
        weight 1
        TCP_CHECK {
	    connect_port 80
	    connect_timeout 3
	    nb_get_retry 3
	    delay_before_retry 4
	}
    }
}
[root@localhost keepalived]# systemctl start keepalived
[root@localhost keepalived]# ip addr show dev ens33
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:11:0d:16 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.21/24 brd 192.168.100.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.100.100/32 brd 192.168.100.100 scope global noprefixroute ens33:0
       valid_lft forever preferred_lft forever
    inet6 fe80::3069:1a3d:774b:18f/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

2.3、配置從排程器

2.3.1、調整/proc 響應引數

[root@localhost network-scripts]# vi /etc/sysctl.conf 
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0
[root@localhost network-scripts]# sysctl -p     
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.ens33.send_redirects = 0

2.3.2、調整keepalived 引數

[root@localhost ~]# yum -y install keepalived ipvsadm
[root@localhost ~]# cd /etc/keepalived/
[root@localhost keepalived]# cp keepalived.conf keepalived.conf.bak
[root@localhost keepalived]# vi keepalived.conf
global_defs {
   router_id HA_TEST_R2
}
vrrp_instance VI_1 {
   state BACKUP
   interface ens33
   virtual_router_id 1
   priority 99
   advert_int 1
   authentication {
      auth_type PASS
      auth_pass 123456
   }
   virtual_ipaddress {
      192.168.100.100
   }
}

virtual_server 192.168.100.100 80 {
    delay_loop 15
    lb_algo rr
    lb_kind DR
    persistence 60
    protocol TCP

    real_server 192.168.100.22 80 {
        weight 1
        TCP_CHECK {
	    connect_port 80
	    connect_timeout 3
	    nb_get_retry 3
	    delay_before_retry 4
	}
    }
    real_server 192.168.100.23 80 {
        weight 1
        TCP_CHECK {
	    connect_port 80
	    connect_timeout 3
	    nb_get_retry 3
	    delay_before_retry 4
	}
    }
}
[root@localhost keepalived]# systemctl start keepalived
[root@localhost keepalived]# ip addr show dev ens33 
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:48:b8:83 brd ff:ff:ff:ff:ff:ff
    inet 192.168.100.20/24 brd 192.168.100.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::e438:b533:985e:cf94/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

2.4、配置儲存伺服器

首先檢視nfs-utils 和rpcbind 是否安裝，若沒有用yum安裝即可
安裝好後啟動兩個服務

[root@localhost ~]# systemctl start nfs
[root@localhost ~]# systemctl start rpcbind
[root@localhost ~]# mkdir /opt/51xit /opt/52xit
[root@localhost ~]# vi /etc/exports
/opt/51xit 192.168.100.0/24(rw,sync)
/opt/52xit 192.168.100.0/24(rw,sync)
[root@localhost ~]# systemctl restart rpcbind
[root@localhost ~]# systemctl restart nfs
[root@localhost ~]# systemctl enable nfs
[root@localhost ~]# systemctl enable rpcbind
[root@localhost ~]# echo "this is www.51xit.top" > /opt/51xit/index.html
[root@localhost ~]# echo "this is www.52xit.top" > /opt/52xit/index.html

2.5、配置節點伺服器

2.5.1、配置虛擬IP地址（VIP）

防火牆和核心防護均關閉，檢視是否安裝nfs-utils

[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost network-scripts]# cp ifcfg-lo ifcfg-lo:0
[root@localhost network-scripts]# vi ifcfg-lo:0
DEVICE=lo:0
IPADDR=192.168.100.100
NETMASK=255.255.255.255
ONBOOT=yes

[root@localhost network-scripts]# ifup lo:0
[root@localhost network-scripts]# ifconfig
        省略部分內容
lo:0: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 192.168.100.100  netmask 255.255.255.255
        loop  txqueuelen 1000  (Local Loopback)
        省略部分內容
[root@localhost network-scripts]# vi /etc/rc.local 
/sbin/route add -host 192.168.100.100 dev lo:0

[root@localhost network-scripts]# route add -host 192.168.100.100 dev lo:0

2.5.2、調整/proc響應引數

[root@localhost network-scripts]# vi /etc/sysctl.conf 
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.default.arp_ignore = 1
net.ipv4.conf.default.arp_announce = 2
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.lo.arp_announce = 2

[root@localhost network-scripts]# sysctl -p

前面配置兩臺節點伺服器都一樣

2.5.3、安裝httpd 掛載測試頁

下面分別掛載兩臺節點伺服器

[root@localhost ~]# showmount -e 192.168.100.24
Export list for 192.168.100.24:
/opt/52xit 192.168.100.0/24
/opt/51xit 192.168.100.0/24
[root@localhost ~]# yum -y install httpd
[root@localhost ~]# mount 192.168.100.24:/opt/51xit /var/www/html/
[root@localhost ~]# vi /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Thu Aug  6 12:23:03 2020
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=a1c935eb-f211-43a5-be35-2a9fef1f6a89 /boot                   xfs     defaults        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
/dev/cdrom /mnt iso9660 defaults 0 0
192.168.100.24:/opt/51xit/ /var/www/html/ nfs defaults,_netdev 0 0
[root@localhost ~]# systemctl start httpd

測試登入是否正常

[root@localhost ~]# showmount -e 192.168.100.24
Export list for 192.168.100.24:
/opt/52xit 192.168.100.0/24
/opt/51xit 192.168.100.0/24
[root@localhost ~]# yum -y install httpd
[root@localhost ~]# mount 192.168.100.24:/opt/52xit /var/www/html/
[root@localhost ~]# vi /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Thu Aug  6 12:23:03 2020
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos-root /                       xfs     defaults        0 0
UUID=a1c935eb-f211-43a5-be35-2a9fef1f6a89 /boot                   xfs     defaults        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
/dev/cdrom /mnt iso9660 defaults 0 0
192.168.100.24:/opt/52xit/ /var/www/html/ nfs defaults,_netdev 0 0
[root@localhost ~]# systemctl start httpd

測試登入是否正常

2.6、實驗驗證

2.6.1、測試主排程器

開啟抓包工具，會發現192.168.100.21主排程器，一直在發VRRP報文

真機瀏覽器輸入192.168.100.100

等一分鐘重新整理或者重新輸入

主排程器正常！！！

2.6.2、測試從排程器

停止主伺服器的keepadlive

[root@localhost keepalived]# systemctl stop keepalived

開啟抓包工具，會發現192.168.100.20從排程器，一直在發VRRP報文

真機瀏覽器輸入192.168.100.100

等一分鐘重新整理或者重新輸入

從排程器正常！！