gjw_apparitor 博客

参考：http://www.f5lab.cn/bbs/viewthread.php?action=printable&tid=487

作者: metoo 时间: 2008-7-21 02:12
通过Election Hash，可以在URI hash分配Cache的基础上，有效的避免Cache服务器的重分布问题。
rules如下：
# Election Hash iRule
# Compute Hash – MD5
# Version 3.0 Dec 4th 2007
#
# MD5 calculation of Server + URI
# Rule selects Server that scores highest
#
# S = Current high score
# N = Node being evaluated
# W = Winning node
#
# Change “myPool” to your pool name.
#

when HTTP_REQUEST {
set S “”
foreach N [active_members -list myPool] {
if { [md5 $N[HTTP::uri]] > $S } {
set S [md5 $N[HTTP::uri]]
set W $N
}
}
pool myPool member [lindex $W 0] [lindex $W 1]
}

优点：避免了原来hash取模的方式，一台设备down掉所有hash表重算的问题。
缺点：每条URI需要计算N次，N=活动的节点数。如果N很大非常耗费CPU资源。