keepalived實現高可用

keepalived

專門做高可用的軟體

高可用

一般是指2臺機器啟動著完全相同的業務系統，當有一臺機器down機了，另外一臺伺服器就能快速的接管，對於訪
問的使用者是無感知的。

高可用軟體

keepalived
heartbeat
RoseHA

keepalived協議

#VRRP ：虛擬路由冗餘協議
VRRP就出現了，我們的VRRP其實是通過軟體或者硬體的形式在Master和Backup外面增加一個虛擬的MAC地址
（VMAC）與虛擬IP地址（VIP），那麼在這種情況下，PC請求VIP的時候，無論是Master處理還是Backup處理，PC
僅會在ARP快取表中記錄VMAC與VIP的資訊。

#keepalived概念
優先順序
如何確定誰是主節點誰是備節點
搶佔式、非搶佔式
如果Master故障，Backup自動接管，那麼Master回覆後會奪權嗎
腦裂
如果兩臺伺服器都認為自己是Master會出現什麼問題
 

部署keepalived高可用軟體

環境準備

keepalived工作原理

1.哪些機器需要做高可用，就要在哪些機器上安裝keepalived
2.keepalived的主節點會心跳檢測（想要證明應用或者主機是否存活）
3.如果心跳檢測失敗，就殺掉自己（keepalived）
4.VIP到備節點上
 

安裝Keepalived

# 1.安裝keepalived
[Tue Aug 10 02:16:50 root@lb01 ~]
 # yum install -y keepalived
[Tue Aug 10 02:16:57 root@lb02 ~]
 # yum install -y keepalived

# 2.修改主節點配置檔案
[Tue Aug 10 03:00:30 root@lb01 ~]
 # vim /etc/keepalived/keepalived.conf
global_defs { #全域性配置
	router_id lb01 #標識身份->名稱
}
	vrrp_instance VI_1 {
		state MASTER #標識角色狀態
		interface eth0 #網絡卡繫結介面
		virtual_router_id 50 #虛擬路由id
		priority 150 #優先順序
		advert_int 1 #監測間隔時間
		authentication { #認證
		auth_type PASS #認證方式
		auth_pass 1111 #認證密碼
	}
	virtual_ipaddress {
		10.0.0.3 #虛擬的VIP地址
	}
}

    
# 3.修改備節點配置檔案
[Tue Aug 10 03:00:36 root@lb02 ~]
 # vim /etc/keepalived/keepalived.conf
global_defs {
    router_id lb02
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 50
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        10.0.0.3
    }
}

# 4.啟動主節點和備節點服務
[Tue Aug 10 03:03:11 root@lb01 ~]
 # systemctl start keepalived
[Tue Aug 10 03:07:47 root@lb02 ~]
 #  systemctl start keepalived

# 5.加入開機自啟
[Tue Aug 10 03:08:10 root@lb01 ~]
 # systemctl enable keepalived
[Tue Aug 10 03:07:49 root@lb02 ~]
 # systemctl enable keepalived
 
# 6.檢視VIP
[Tue Aug 10 03:08:10 root@lb01 ~]
 # ip a
 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group
default qlen 1000
link/ether 00:0c:29:17:c4:b7 brd ff:ff:ff:ff:ff:ff
inet 10.0.0.5/24 brd 10.0.0.255 scope global noprefixroute eth0
valid_lft forever preferred_lft forever
inet 10.0.0.3/32 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:fe17:c4b7/64 scope link
valid_lft forever preferred_lft forever

# 7.檢測IP是否可以漂移
[Tue Aug 10 03:11:05 root@lb01 ~]
 # systemctl stop keepalieved
 

主節點和備節點的配置檔案區別

非搶佔式配置

[root@lb01 conf.d]# vim /etc/keepalived/keepalived.conf
global_defs {
	router_id lb01
}
	vrrp_instance VI_1 {
	state BACKUP
	nopreempt
	interface eth0
	virtual_router_id 50
	priority 150
	advert_int 1
	authentication {
		auth_type PASS
		auth_pass 1111
	}
virtual_ipaddress {
		10.0.0.3
	}
}

[root@lb02 conf.d]# vim /etc/keepalived/keepalived.conf
global_defs {
	router_id lb02
}
	vrrp_instance VI_1 {
	state BACKUP
	nopreempt
	interface eth0
	virtual_router_id 50
	priority 100
	advert_int 1
	authentication {
		auth_type PASS
		auth_pass 1111
	}
	virtual_ipaddress {
		10.0.0.3
	}
}

keepalived結合nginx實現負載均衡的高可用

## 1.編寫監聽nginx的指令碼
[root@lb01 ~]# vim /root/check.sh
#!/bin/bash
nginx_num=$(ps -ef|grep [n]ginx|wc -l)

if [ $nginx_num -eq 0 ];then
        systemctl stop keepalived
fi
## 2.修改主節點的配置檔案
[Tue Aug 10 03:24:57 root@lb01 ~]
 # vim /etc/keepalived/keepalived.conf
global_defs {                   #全域性配置
    router_id lb01              #標識身份->名稱
}

vrrp_script check_web {
    # 指令碼路徑
    script "/root/check.sh"
    # 檢測時間（每5秒執行一次檢測指令碼）
    interval 5
}


vrrp_instance VI_1 {
    state MASTER                #標識角色狀態
    interface eth0              #網絡卡繫結介面
    virtual_router_id 50        #虛擬路由id
    priority 150                #優先順序
    advert_int 1                #監測間隔時間
    authentication {            #認證
        auth_type PASS          #認證方式
        auth_pass 1111          #認證密碼
    }

    track_script {
        check_web
    }

    virtual_ipaddress {
        10.0.0.3                #虛擬的VIP地址
    }
}

## 3.重啟keepalived
[root@lb01 ~]# systemctl restart keepalived

## 4.給指令碼執行許可權
[root@lb01 ~]# chmod +x /root/check.sh

腦裂故障

由於某些原因，導致兩臺keepalived高可用伺服器在指定時間內，無法檢測到對方的心跳，個字去的資源及服務的所
有權，而此時的兩臺高可用伺服器又都還活著。
1、伺服器網線鬆動等網路故障 2、伺服器硬體故障發生損壞現象而崩潰 3、主備都開啟firewalld防火牆