• 采用单线程、事件驱动、非阻塞模型，减少上下文切换的消耗，能在1ms内处理数百个请求。并且每个会话只占用数KB的内存。
• 大量精细的性能优化，如O(1)复杂度的事件检查器、延迟更新技术、Single-buffereing、Zero-copy forwarding等等，这些技术使得HAProxy在中等负载下只占用极低的CPU资源。
• HAProxy大量利用操作系统本身的功能特性，使得其在处理请求时能发挥极高的性能，通常情况下，HAProxy自身只占用15%的处理时间，剩余的85%都是在系统内核层完成的。
• HAProxy作者在8年前（2009）年使用1.4版本进行了一次测试，单个HAProxy进程的处理能力突破了10万请求/秒，并轻松占满了10Gbps的网络带宽。

 #---------------------------------------------------------------------

 # 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:

     #

     # ) configure syslog to accept network log events.  This is done

     #    by adding the '-r' option to the SYSLOGD_OPTIONS in

     #    /etc/sysconfig/syslog

     #

     # ) 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    //定义日志选项，这里是通过log server来记录日志的

     chroot      /var/lib/haproxy      //切换目录至/var/lib/haproxy下以安全方式运行

     pidfile     /var/run/haproxy.pid

     maxconn     4000       //最大连接数

     user        haproxy    //进程启动后以haproxy的身份运行

     group       haproxy

     daemon     //启动为守护进程，如果没有此选项那么haproxy将运行在前台

     # turn on stats unix socket     //表示本地访问stats(统计数据)时可以基于共享内存进行通信

     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/

     option                  redispatch

     retries

     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                 

 #---------------------------------------------------------------------

 # main frontend which proxys to the backends

 #---------------------------------------------------------------------

 frontend  main *:5000   //main是frontend的名字，*表示本机的所有地址，5000表示对应主机的端口

     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    //static是backend的名字，如果frontend调用的后端服务器的时候可以直接调用static

     balance     roundrobin

     server      static 127.0.0.1: check

 #---------------------------------------------------------------------

 # round robin balancing between the various backends

 #---------------------------------------------------------------------

 backend app

     balance     roundrobin

     server  app1 127.0.0.1: check

     server  app2 127.0.0.1: check

     server  app3 127.0.0.1: check

     server  app4 127.0.0.1: check

前面的不修改
 1 #---------------------------------------------------------------------

 # main frontend which proxys to the backends

 #---------------------------------------------------------------------

 frontend  main *:80

     default_backend        websrvs     //调用backend的名字

 #---------------------------------------------------------------------

 # static backend for serving up images, stylesheets and such

 #---------------------------------------------------------------------

 backend websrvs      //websrvs是backend的名字

     balance        roundrobin

     server   web1  192.168.184.142:80  check    //server也应该有自己的名字，这里是web1，check表示要做健康状态检查

     server   web2  192.168.184.143:80  check