基于HAproxy的 session同步实践
首先安装，启动，配置HAproxy的方法网上已经有很多的介绍，此处不再作过多阐述推荐2个比较有用的安装配置资料：
安装说明
http://blog.chinaunix.net/uid-17291169-id-4744949.html
配置文件说明
http://www.iyunv.com/Linux/2012-07/65350.htm
另附简单操作代码
重启 关闭 与 启动
service haproxy start/stop/restart
查询状态
service haproxy status
OK，前期工作准备完成，下面来描述一下测试环境
工程1：http://192.168.28.151:1199/TestHa/
工程2：http://192.168.28.151:2299/TestHa/
利用HaProxy做负载均衡，并且配置session同步
以下是HaProsy的配置文件
#---------------------------------------------------------------------
# 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
#---------------------------------------------------------------------
#此处配置HAProxy的监听端口
frontendmain *:5000
acl url_static path_beg -i /static /images /javascript /stylesheets
acl url_static path_end -i .jpg .gif .png .css .js
use_backend static if url_static
default_backend app
#---------------------------------------------------------------------
# static backend for serving up images, stylesheets and such
#---------------------------------------------------------------------
backend static
balance roundrobin
server static 127.0.0.1:4331 check
#---------------------------------------------------------------------
# round robin balancing between the various backends
#---------------------------------------------------------------------
backend app
appsession JSESSIONID len 64 timeout 5h request-learn#必配
serverapp1 192.168.28.151:1199 cookie app1 check#必配
serverapp2 192.168.28.151:2299 cookie app2 check#必配
# option httpchk GET /index.html
listen status 192.168.28.151:8899
stats enable
stats uri /stats
stats auth admin:123456
stats admin if TRUE
stats realm (Haproxy\ statistic)
配置完成后测试一下结果
访问 http://192.168.28.151:5000/TestHa/
可见此过程中的三次跳转，HaProxy已经根据sessionid将本次会话都分配给了同一台机器。
那么我们再换一个浏览器测试一下负载均衡
新的浏览器建立的新的会话被负载到了另外一个端口上。
实验至此并未结束，实际上HAProxy为我们提供了3种方法来实现session共享
[*]用户IP 识别
[*]cookie 识别
[*]session 识别
个人觉得前两种比较有局限性，第一种根据ip来分配，在ip变动的时候将会失去这种session一致性。第二种方法将一个cookie头植入客户端，倘若客户端禁用cookie那么也无法实现
详细的关于这三种方法可以阅读
http://itindex.net/blog/2012/07/24/1343118758531.html
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