Keepalived基礎使用教程

高可用：兩臺業務系統啓動着相同的服務，如果有一臺故障，另一臺自動接管,我們將將這個稱之爲高可用；

Keekpalived工作原理：通過vrrp協議實現

 

vrrp原理

vrrp抓包

Keepalived工作方式：搶佔式、非搶佔式

安裝：yum install keepalived -y

日誌存放位置：/var/log/messages

1、keepaliaved 搶佔式配置

master配置

[root@lb01 ~]# rpm -qc keepalived
/etc/keepalived/keepalived.conf
/etc/sysconfig/keepalived
[root@lb01 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb02 #標識信息，一個名字而已；
}
vrrp_instance VI_1 {
    state MASTER    #角色是master
    interface eth0  #vip 綁定端口
    virtual_router_id 50    #讓master 和backup在同一個虛擬路由裏，id 號必須相同；
    priority 150            #優先級,誰的優先級高誰就是master ;
    advert_int 1            #心跳間隔時間
    authentication {
        auth_type PASS      #認證
        auth_pass 1111      #密碼 
}
    virtual_ipaddress {
        10.0.0.3            #虛擬ip
    }
}

 

backup配置

[root@lb02 ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
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
    }
}

[root@lb02 ~]# 

 

2、Keepalived非搶佔式配置：

非搶佔式不再有主從之分，全部都爲BACKUP,並且配置文件中添加nopreempt，用來標識爲非搶佔式；

[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb01
}

vrrp_instance VI_1 {
    state MASTER
    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 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {     
    router_id lb02   
}

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

You have new mail in /var/spool/mail/root
[root@lb02 /etc/nginx/upstream]# 

 

3、nginx+keepalived

實現思路：將keepalived 中的vip作爲nginx負載均衡的監聽地址，並且域名綁定的也是vip的地址。

說明：Nginx 負載均衡實現高可用，需要藉助Keepalived地址漂移功能。

在不考慮後端數據庫和存儲的時候如下架構

keepalived+Nginx

兩臺負載均衡配置：

 

[root@lb01 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:97:e1:ff brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.5/24 brd 10.0.0.255 scope global 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:fe97:e1ff/64 scope link 
       valid_lft forever preferred_lft forever
[root@lb01 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb01
}

vrrp_instance VI_1 {
    state MASTER
    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@lb01 /etc/nginx/upstream]# 

[root@lb02 /etc/nginx/upstream]# ip add show eth0
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:0c:29:6f:18:48 brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.6/24 brd 10.0.0.255 scope global eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe6f:1848/64 scope link 
       valid_lft forever preferred_lft forever
[root@lb02 /etc/nginx/upstream]# cat /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {     
    router_id lb02   
}

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

[root@lb02 /etc/nginx/upstream]# 

 

4、keepalived腦裂現象

由於某些原因，導致兩臺keepalived高可用服務器在指定時間內，無法檢測到對方存活心跳信息，從而導致互相搶佔對方的資源和服務所有權，然而此時兩臺高可用服務器有都還存活。
可能出現的原因：
1、服務器網線鬆動等網絡故障；
2、服務器硬件故障發生損壞現象而崩潰；
3、主備都開啓了firewalld 防火牆。
4、在Keepalived+nginx 架構中，當Nginx宕機，會導致用戶請求失敗，但是keepalived不會進行切換，
所以需要編寫一個檢測nginx的存活狀態的腳本，如果nginx不存活，則kill掉宕掉的nginx主機上面的keepalived。(所有的keepalived都要配置)

架構如下：

 

 

腳本如下：

[root@lb01 /server/scripts]# cat /server/scripts/check_list 
#!/bin/sh

nginxpid=$(ps -C nginx --no-header|wc -l)
#1.判斷Nginx是否存活,如果不存活則嘗試啓動Nginx
if [ $nginxpid -eq 0 ];then
    systemctl start nginx
    sleep 3
    #2.等待3秒後再次獲取一次Nginx狀態
    nginxpid=$(ps -C nginx --no-header|wc -l) 
    #3.再次進行判斷, 如Nginx還不存活則停止Keepalived,讓地址進行漂移,並退出腳本  
    if [ $nginxpid -eq 0 ];then
        systemctl stop keepalived
   fi
fi
[root@lb01 /server/scripts]# 

配置文件如下：

[root@lb01 /server/scripts]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
    router_id lb01
}

vrrp_script check {
    script "/server/scripts/check_list"
    interval  10


}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 50
    priority 150
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
}
    virtual_ipaddress {
        10.0.0.3
    }
    track_script  {
    check
}
}
[root@lb01 /server/scripts]#