运维进行时

一、前言
       Haproxy是稳定、高性能、高可用性的负载均衡解决方案，支持HTTP及TCP代理后端服务器池，因支持强大灵活的7层acl规则，广泛作为HTTP反向代理。本文则详细介绍如何利用它的四层交换与Keepalived实现一个负载均衡器，适用于Socket、ICE、Mail、Mysql、私有通讯等任意TCP服务。系统架构图如下：

A brand new Rails/Merb app you put together over a weekend, a pack of Mongrels, a reverse proxy (like Nginx), and you're up and running. Well, almost, what about that one request that tends to run forever, often forcing the user to double check their internet connection? Response time is king, and you always want to make sure that your site feel snappy to the user. Did you know that Flickr optimizes all of their pages to render in sub 250ms?
When you're fighting with response times, the worst thing you can possibly do is queue up another request behind an already long running process. Not only does the first request take forever, but everyone else must wait in line for it to finish as well! To mitigate the problem HAProxy goes beyond a simple round-robin scheduler, and implements a very handy feature: intelligent request queuing!

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更多http://www.igvita.com/2008/05/13/load-balancing-qos-with-haproxy/