Apache的ReWrite的应用mod_rewrite模块使用（12）

大型虚拟主机
说明:
Apache的功能很强，在有几十个虚拟主机的情况下运行得很好，但是如果你是ISP，需要提供几百个虚拟主机，那么这就不是一个最佳的选择了。
方案:
为此，需要用代理吞吐(Proxy Throughput)功能(flag [P])映射远程页面甚至整个远程网络区域到自己的名称空间：
代码:
##
## vhost.map
##
www.vhost1.dom:80 /path/to/docroot/vhost1
www.vhost2.dom:80 /path/to/docroot/vhost2
:
www.vhostN.dom:80 /path/to/docroot/vhostN
代码:
##
## httpd.conf
##
:
# use the canonical hostname on redirects, etc.
UseCanonicalName on
:
# add the virtual host in front of the CLF-format
CustomLog /path/to/access_log "％e ％h ％l ％u ％t "％r" ％>s ％b"
:
# enable the rewriting engine in the main server
RewriteEngine on
# define two maps: one for fixing the URL and one which defines
# the available virtual hosts with their corresponding
# DocumentRoot.
RewriteMap lowercase int:tolower
RewriteMap vhost txt:/path/to/vhost.map
# Now do the actual virtual host mapping
# via a huge and complicated single rule:
#
# 1. make sure we don't map for common locations
RewriteCond ％ !^/commonurl1/.*
RewriteCond ％ !^/commonurl2/.*
:
RewriteCond ％ !^/commonurlN/.*
#
# 2. make sure we have a Host header, because
# currently our approach only supports
# virtual hosting through this header
RewriteCond ％ !^$
#
# 3. lowercase the hostname
RewriteCond $|NONE} ^(.+)$
#
# 4. lookup this hostname in vhost.map and
# remember it only when it is a path
# (and not "NONE" from above)
RewriteCond $ ^(/.*)$
#
# 5. finally we can map the URL to its docroot location
# and remember the virtual host for logging puposes
RewriteRule ^/(.*)$ ％1/$1 [E=VHOST:$}]
:
对访问的限制
阻止Robots
说明:
如何阻止一个完全匿名的robot取得特定网络区域的页面？一个/robots.txt文件可以包含若干"Robot Exclusion Protocol(robot排除协议)"的行，但不足以阻止此类robot。
方案:
可以用一个规则集以拒绝对网络区域/~quux/foo/arc/(对一个很深的目录区域进行列表可能会使服务器产生很大的负载)的访问。还必须确保仅阻止特定的robot，就是说，仅仅阻止robot访问主机是不够的，这样会同时也阻止了用户访问该主机。为此，就需要对HTTP头的User-Agent信息作匹配。
代码:
RewriteCond ％ ^NameOfBadRobot.*
RewriteCond ％ ^123.45.67.[8-9]$
RewriteRule ^/~quux/foo/arc/.+ - [F]