HA之keepalived
Keepalivedkeepalived是一个类似于layer3, 4 & 7交换机制的软件，也就是我们平时说的第3层、第4层和第7层交换。Keepalived的作用是检测服务器的状态，如果有一台web服务器死机，或工作出现故障，Keepalived将检测到，并将有故障的服务器从系统中剔除，同时使用其他服务器代替该服务器的工作，当服务器工作正常后Keepalived自动将服务器加入到服务器群中，这些工作全部自动完成，不需要人工干涉，需要人工做的只是修复故障的服务器。
原理基于：VRRP技术（VRRP虚拟路由）
VRRP的优势：
冗余：可以使用多个路由器设备作为LAN客户端的默认网关，大大降低了默认网关成为单点故障的可能性；
负载共享：允许来自LAN客户端的流量由多个路由器设备所共享；
多VRRP组：在一个路由器物理接口上可配置多达255个VRRP组；
多IP地址：基于接口别名在同一个物理接口上配置多个IP地址，从而支持在同一个物理接口上接入多个子网；
抢占：在master故障时允许优先级更高的backup成为master；
通告协议：使用IANA所指定的组播地址224.0.0.18进行VRRP通告；
VRRP追踪：基于接口状态来改变其VRRP优先级来确定最佳的VRRP路由器成为master；
一、安装
keepalived的安装比较简单，再次不做过多介绍。
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tar -zxvf keepalived-1.2.7.tar.gz
cd keepalived-1.2.7
./configure --prefix=/usr/local/keepalived
make
make install
如果想让keepalived关联更多功能，可以参考官方网站的相关介绍：http://www.keepalived.org/
二、配置keepalived
1、配置keepalived为实现haproxy高可用的配置文件示例：
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! Configuration File for keepalived
global_defs {
notification_email {
sunshine@foxmail.com
}
notification_email_from kanotify@sunshine.com
smtp_connect_timeout 3
smtp_server 127.0.0.1
router_id LVS_DEVEL
}
vrrp_script chk_haproxy {
script "killall -0 haproxy"
interval 1
weight 2
}
vrrp_script chk_mantaince_down {
script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
interval 1
weight 2
}
vrrp_instance VI_1 {
interface eth0
state MASTER# BACKUP for slave routers
priority 101# 100 for BACKUP
virtual_router_id 51
garp_master_delay 1
authentication {
auth_type PASS
auth_pass password
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.100.1/16 dev eth0 label eth0:0
}
track_script {
chk_haproxy
chk_mantaince_down
}
notify_master "/etc/keepalived/notify.sh master"
notify_backup "/etc/keepalived/notify.sh backup"
notify_fault "/etc/keepalived/notify.sh fault"
}
注意：
1）上面的state为当前节点的起始状态，通常在master/slave的双节点模型中，其一个默认为MASTER，而别一个默认为BACKUP。
2）priority为当关节点在当前虚拟路由器中的优先级，master的优先级应该大于slave的；
下面是一个notify.sh脚本的简单示例：
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#!/bin/bash
# description: An example of notify script
#
vip=172.16.100.1
contact='root@localhost'
Notify() {
mailsubject="`hostname` to be $1: $vip floating"
mailbody="`date '+%F %H:%M:%S'`: vrrp transition, `hostname` changed to be $1"
echo $mailbody | mail -s "$mailsubject" $contact
}
case "$1" in
master)
notify master
/etc/rc.d/init.d/haproxy start
exit 0
;;
backup)
notify backup
/etc/rc.d/init.d/haproxy restart
exit 0
;;
fault)
notify fault
exit 0
;;
*)
echo 'Usage: `basename $0` {master|backup|fault}'
exit 1
;;
esac
2、配置keepalived为实现haproxy高可用的双主模型配置文件示例：
说明：其基本实现思想为创建两个虚拟路由器，并以两个节点互为主从。
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! Configuration File for keepalived
global_defs {
notification_email {
sunshine@foxmail.com
}
notification_email_from kanotify@sunshine.com
smtp_connect_timeout 3
smtp_server 127.0.0.1
router_id LVS_DEVEL
}
vrrp_script chk_haproxy {
script "killall -0 haproxy"
interval 1
weight 2
}
vrrp_script chk_mantaince_down {
script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
interval 1
weight 2
}
vrrp_instance VI_1 {
interface eth0
state MASTER# BACKUP for slave routers
priority 101# 100 for BACKUP
virtual_router_id 51
garp_master_delay 1
authentication {
auth_type PASS
auth_pass password
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.100.1/16 dev eth0 label eth0:0
}
track_script {
chk_haproxy
chk_mantaince_down
}
notify_master "/etc/keepalived/notify.sh master"
notify_backup "/etc/keepalived/notify.sh backup"
notify_fault "/etc/keepalived/notify.sh fault"
}
vrrp_instance VI_2 {
interface eth0
state BACKUP# BACKUP for slave routers
priority 100# 100 for BACKUP
virtual_router_id 52
garp_master_delay 1
authentication {
auth_type PASS
auth_pass password
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.100.2/16 dev eth0 label eth0:1
}
track_script {
chk_haproxy
chk_mantaince_down
}
}
说明：
1）对于VI_1和VI_2来说，两个节点要互为主从关系；
3、LVS + keepalived的实现：
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! Configuration File for keepalived
global_defs {
notification_email {
sunshine@foxmail.com
}
notification_email_from kanotify@sunshine.com
smtp_connect_timeout 3
smtp_server 127.0.0.1
router_id LVS_DEVEL
}
vrrp_script chk_schedown {
script "[[ -f /etc/keepalived/down ]] && exit 1 || exit 0"
interval 2
weight -2
}
vrrp_instance VI_1 {
interface eth0
state MASTER
priority 101
virtual_router_id 51
garp_master_delay 1
authentication {
auth_type PASS
auth_pass password
}
track_interface {
eth0
}
virtual_ipaddress {
172.16.100.1/16 dev eth0 label eth0:0
}
track_script {
chk_schedown
}
}
virtual_server 172.16.100.1 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 50
protocol TCP
# sorry_server 192.168.200.200 1358
real_server 172.16.100.11 80 {
weight 1
HTTP_GET {
url {
path /
status_code 200
}
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
real_server 172.16.100.12 80 {
weight 1
HTTP_GET {
url {
path /
status_code 200
}
connect_timeout 3
nb_get_retry 3
delay_before_retry 3
}
}
}
如果要使用TCP_CHECK检测各realserver的健康状态，那么，上面关于realserver部分的定义也可以替换为如下内容：
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virtual_server 172.16.100.1 80 {
delay_loop 6
lb_algo rr
lb_kind DR
persistence_timeout 300
protocol TCP
sorry_server 127.0.0.1 80
real_server 172.16.100.11 80 {
weight 1
TCP_CHECK {
tcp_port 80
connect_timeout 3
}
}
real_server 172.16.100.12 80 {
weight 1
TCP_CHECK {
connect_port 80
connect_timeout 3
}
}
}
说明：其中的sorry_server是用于定义所有realserver均出现故障时所用的服务器。
三、keepalived通知脚本示例：
下面的脚本可以接受选项，其中：
-s, --service SERVICE,...：指定服务脚本名称，当状态切换时可自动启动、重启或关闭此服务；
-a, --address VIP: 指定相关虚拟路由器的VIP地址；
-m, --mode {mm|mb}：指定虚拟路由的模型，mm表示主主，mb表示主备；它们表示相对于同一种服务而方，其VIP的工作类型；
-n, --notify {master|backup|fault}：指定通知的类型，即vrrp角色切换的目标角色；
-h, --help：获取脚本的使用帮助；
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#!/bin/bash
# description: An example of notify script
# Usage: notify.sh -m|--mode {mm|mb} -s|--service SERVICE1,... -a|--address VIP-n|--notify {master|backup|falut} -h|--help
helpflag=0
serviceflag=0
modeflag=0
addressflag=0
notifyflag=0
contact='root@localhost'
Usage() {
echo "Usage: notify.sh [-m|--mode {mm|mb}] [-s|--service SERVICE1,...] <-a|--address VIP><-n|--notify {master|backup|falut}>"
echo "Usage: notify.sh -h|--help"
}
ParseOptions() {
local I=1;
if [ $# -gt 0 ]; then
while [ $I -le $# ]; do
case $1 in
-s|--service)
[ $# -lt 2 ] && return 3
serviceflag=1
services=(`echo $2|awk -F"," '{for(i=1;i<=NF;i++) print $i}'`)
shift 2 ;;
-h|--help)
helpflag=1
return 0
shift
;;
-a|--address)
[ $# -lt 2 ] && return 3
addressflag=1
vip=$2
shift 2
;;
-m|--mode)
[ $# -lt 2 ] && return 3
mode=$2
shift 2
;;
-n|--notify)
[ $# -lt 2 ] && return 3
notifyflag=1
notify=$2
shift 2
;;
*)
echo "Wrong options..."
Usage
return 7
;;
esac
done
return 0
fi
}
#workspace=$(dirname $0)
RestartService() {
if [ ${#@} -gt 0 ]; then
for I in $@; do
if [ -x /etc/rc.d/init.d/$I ]; then
/etc/rc.d/init.d/$I restart
else
echo "$I is not a valid service..."
fi
done
fi
}
StopService() {
if [ ${#@} -gt 0 ]; then
for I in $@; do
if [ -x /etc/rc.d/init.d/$I ]; then
/etc/rc.d/init.d/$I stop
else
echo "$I is not a valid service..."
fi
done
fi
}
Notify() {
mailsubject="`hostname` to be $1: $vip floating"
mailbody="`date '+%F %H:%M:%S'`, vrrp transition, `hostname` changed to be $1."
echo $mailbody | mail -s "$mailsubject" $contact
}
# Main Function
ParseOptions $@
[ $? -ne 0 ] && Usage && exit 5
[ $helpflag -eq 1 ] && Usage && exit 0
if [ $addressflag -ne 1 -o $notifyflag -ne 1 ]; then
Usage
exit 2
fi
mode=${mode:-mb}
case $notify in
'master')
if [ $serviceflag -eq 1 ]; then
RestartService ${services[*]}
fi
Notify master
;;
'backup')
if [ $serviceflag -eq 1 ]; then
if [ "$mode" == 'mb' ]; then
StopService ${services[*]}
else
RestartService ${services[*]}
fi
fi
Notify backup
;;
'fault')
Notify fault
;;
*)
Usage
exit 4
;;
esac
在keepalived.conf配置文件中，其调用方法如下所示：
notify_master "/etc/keepalived/notify.sh -n master -a 172.16.100.1"
notify_backup "/etc/keepalived/notify.sh -n backup -a 172.16.100.1"
notify_fault "/etc/keepalived/notify.sh -n fault -a 172.16.100.1"
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