基于keepalived对HAproxy做高可用集群
一、Keepalived简介Keepalived的作用是检测web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web服务器从系统中剔除，当web服务器工作正常后Keepalived自动将web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web服务器。
Layer3,4&7工作在IP/TCP协议栈的IP层，TCP层，及应用层,原理分别如下：
Layer3：Keepalived使用Layer3的方式工作式时，Keepalived会定期向服务器群中的服务器发送一个ICMP的数据包（既我们平时用的Ping程序）,如果发现某台服务的IP地址没有激活，Keepalived便报告这台服务器失效，并将它从服务器群中剔除，这种情况的典型例子是某台服务器被非法关机。Layer3的方式是以服务器的IP地址是否有效作为服务器工作正常与否的标准。在本文中将采用这种方式。
Layer4:如果您理解了Layer3的方式，Layer4就容易了。Layer4主要以TCP端口的状态来决定服务器工作正常与否。如web server的服务端口一般是80，如果Keepalived检测到80端口没有启动，则Keepalived将把这台服务器从服务器群中剔除。
Layer7：Layer7就是工作在具体的应用层了，比Layer3,Layer4要复杂一点，在网络上占用的带宽也要大一些。Keepalived将根据用户的设定检查服务器程序的运行是否正常，如果与用户的设定不相符，则Keepalived将把服务器从服务器群中剔除。
二、安装配置
1.拓扑图
http://s3.运维网.com/wyfs02/M00/25/90/wKioL1Nkn6eyMZ4OAAChbkfDbog261.jpg
说明：1.两个代理服务器通过VIP向外提供数据
2.两个代理服务器都可以代理后端的服务器
3.为测试方便，后端服务器至提供静态页面
2.ip规划
功用ip地址安装软件VIP192.168.1.99
反向代理1192.168.1.201keepalived、haproxy反向代理2192.168.1.204keepalived、haproxyweb服务器1192.168.1.202httpdweb服务器2192.168.1.203httpd 3.安装配置haproxy
关于haproxy的详细配置，请参照http://wangfeng7399.blog.运维网.com/3518031/1405758
# cat /etc/haproxy/haproxy.cfg
#---------------------------------------------------------------------
# Example configuration for a possible web application.See the
# full configuration options online.
#
# http://haproxy.1wt.eu/download/1.4/doc/configuration.txt
#
#---------------------------------------------------------------------
#---------------------------------------------------------------------
# Global settings
#---------------------------------------------------------------------
global
# to have these messages end up in /var/log/haproxy.log you will
# need to:
#
# 1) configure syslog to accept network log events.This is done
# by adding the '-r' option to the SYSLOGD_OPTIONS in
# /etc/sysconfig/syslog
#
# 2) configure local2 events to go to the /var/log/haproxy.log
# file. A line like the following can be added to
# /etc/sysconfig/syslog
#
# local2.* /var/log/haproxy.log
#
log 127.0.0.1 local2
chroot /var/lib/haproxy
pidfile /var/run/haproxy.pid
maxconn 4000
user haproxy
group haproxy
daemon
# turn on stats unix socket
stats socket /var/lib/haproxy/stats
#---------------------------------------------------------------------
# common defaults that all the 'listen' and 'backend' sections will
# use if not designated in their block
#---------------------------------------------------------------------
defaults
mode http
log global
option httplog
option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
retries 3
timeout http-request 10s
timeout queue 1m
timeout connect 10s
timeout client 1m
timeout server 1m
timeout http-keep-alive 10s
timeout check 10s
maxconn 3000
#---------------------------------------------------------------------
# main frontend which proxys to the backends
#---------------------------------------------------------------------
frontendmain *:80
default_backend static
#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
backend static
balance roundrobin
server node2 192.168.1.202:80 check maxconn 2000
server node3 192.168.1.203:80 check maxconn 2000
#---------------------------------------------------------------------
# round robin balancing between the various backends
#--------------------------------------------------------------------- 说明：两个节点的HAproxy的配置文件应该保持一样
4.测试haproxy的配置
http://s3.运维网.com/wyfs02/M01/25/90/wKiom1NkqEjjye6UAAB5vROjfcc126.jpg
http://s3.运维网.com/wyfs02/M00/25/90/wKioL1NkqB7yeQdHAAByUqYSatI357.jpg
5.安装配置keepalived
①、安装keepalived
keepalived的安装可以通过yum源来安装，也可以通过编译源码来安装，本处通过yum源赖安装
②、配置keepalived主节点
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {//全局参数
notification_email { //邮件
sysadmin@firewall.loc //收件人地址
}
notification_email_from Alexandre.Cassen@firewall.loc //发件人地址
smtp_server 127.0.0.1//邮件服务器的地址
smtp_connect_timeout 30//间隔时间
router_id LVS_DEVEL//邮件服务器的组的id
}
vrrp_script chk_haproxy {
script "killall -0 haproxy"//检查haproxy是否在线
interval 1 //检查间隔时间
weight -5 //如果检查失败，则权重-5
}
vrrp_instance VI_1 { //定义第一个集群
state MASTER //初始状态为主节点，从节点应该为BACKUP
interface eth0 //配置ip的端口
virtual_router_id 51//本组集群的id号，主从节点必须一样
priority 100 //主节点的优先级，备用节点的优先级必须低于主节点
advert_int 1 //心跳检查间隔时间
authentication {
auth_type PASS //通信为明文密码通信
auth_pass 1111 //通信的密码，主从节点必须一样
}
virtual_ipaddress {
192.168.1.99 //定义一个VIP
}
track_script { //调用上面的命令
chk_haproxy
}
} ③、配置keepalived从节点
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived
global_defs {
notification_email {
sysadmin@firewall.loc
}
notification_email_from Alexandre.Cassen@firewall.loc
smtp_server 127.0.0.1
smtp_connect_timeout 30
router_id LVS_DEVEL
}
vrrp_script chk_haproxy {
script "killall -0 haproxy"
interval 1
weight -5
}
vrrp_instance VI_1 {
state BACKUP
interface eth0
virtual_router_id 51
priority 99
advert_int 1
authentication {
auth_type PASS
auth_pass 1111
}
virtual_ipaddress {
192.168.1.99
}
track_script {
chk_haproxy
}
} 6.测试
2: eth0:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:56:78:cd brd ff:ff:ff:ff:ff:ff
inet 192.168.1.204/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.99/32 scope global eth0
inet6 fe80::20c:29ff:fe56:78cd/64 scope link tentative dadfailed
valid_lft forever preferred_lft forever 可以看到ip地址已经配置上去了
http://s3.运维网.com/wyfs02/M02/25/91/wKioL1Nkr17zGRQ-AACGBxHygoA656.jpg
我们可以看到网页访问正常
下面，我们模拟服务器损坏，将node1上的haproxy关掉，看看ip地址是否会转移到node4上
# ip add
1: lo:mtu 16436 qdisc noqueue state UNKNOWN
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0:mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 00:0c:29:56:78:cd brd ff:ff:ff:ff:ff:ff
inet 192.168.1.204/24 brd 192.168.1.255 scope global eth0
inet 192.168.1.99/32 scope global eth0
inet6 fe80::20c:29ff:fe56:78cd/64 scope link tentative dadfailed
valid_lft forever preferred_lft forever 查看网页是否能够访问正常 http://s3.运维网.com/wyfs02/M01/25/90/wKiom1NksguiuvRCAACLwWl-ptU734.jpg
OK！！可以看到我们的页面访问正常，这就可以实现当前段的一个反向代理服务器宕机或者后端的一个web服务宕机，服务都可以正常对外提供
7.扩展
我们还可以自定义通知机制
#!/bin/bash
# Author: wangfeng7399
# description: An example of notify script
#
vip=192.168.1.99
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
exit 0
;;
backup)
notify backup
exit 0
;;
fault)
notify fault
exit 0
;;
*)
echo 'Usage: `basename $0` {master|backup|fault}'
exit 1
;;
esac 在keepalived的配置文件中通过notify来调用，如下所示
notify_master "/etc/keepalived/notify.sh master"
notify_backup "/etc/keepalived/notify.sh backup"
notify_fault "/etc/keepalived/notify.sh fault" 大功告成，由于本人水平有限，可能有逻辑上的错误，请各位大神匹配指正
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