performance when using a .htaccess
Lisa Kachold
lisakachold at obnosis.com
Fri Oct 22 20:18:34 MST 2010
On Fri, Oct 22, 2010 at 4:00 PM, Lisa Kachold <lisakachold at obnosis.com>wrote:
>
>
> On Fri, Oct 22, 2010 at 2:18 PM, keith smith <klsmith2020 at yahoo.com>wrote:
>
>>
>>
>> Hi,
>>
>> I have a question about performance when using a .htaccess file. I have
>> read that having multiple .htaccess files can slow Apache. Meaning a
>> .htaccess file in each directory.
>>
>> We have moved a ton of content, upwards of 900 pages. About 600 of those
>> have been moved from our blog which was located in the directory /blog. It
>> was suggested to break the .htaccess into files that reflect the content
>> moved. For example put a .htaccess file in the /blog directory that
>> reflects all the content from the blog instead of one big .htaccess file in
>> the doc root directory that would contain 900 redirects.
>>
>
> Well, that's better than FollowSymlinks?
>
> The reason that multiple .htaccess file management can be slow and
> difficult is that Apache2 searches each TREE and .htaccess files are
> inherited from hierarchical directories.
>
> A rewrite might actually be able to do exactly what you need? have you
> considered that? Rewrite overhead is not huge, especially if you are
> caching for this /blog URL?
>
>
You simply enable mod_rewrite in Apache2 (procedure varies depending on your
distro/version).
A mod_rewrite solution is ONE line entry in your configuration file for that
VirtualHost (for instance):
1) Here's a simple rewrite (provided your directory BLOG containing all of
the 600 files can be trivially redirected to something like "newblog" ).
RewriteEngine on
RewriteBase /blog/
RewriteRule ^*/newblog/* $R1
Rewrite all files from one URL "blog" with a R permanent redirect to
/blogs/?
2) Use a RewriteMap which is loaded ONCE by Apache:
http://httpd.apache.org/docs/2.0/mod/mod_rewrite.html#rewritemap
The RewriteMap directive defines a *Rewriting Map* which can be used inside
rule substitution strings by the mapping-functions to insert/substitute
fields through a key lookup. The source of this lookup can be of various
types.
The *MapName* is the name of the map and will be used to specify a
mapping-function for the substitution strings of a rewriting rule via one of
the following constructs:
*${ MapName : LookupKey }
${ MapName : LookupKey | DefaultValue }*
When such a construct occurs, the map *MapName* is consulted and the key *
LookupKey* is looked-up. If the key is found, the map-function construct is
substituted by *SubstValue*. If the key is not found then it is substituted
by *DefaultValue* or by the empty string if no *DefaultValue* was specified.
For example, you might define a RewriteMap as:
RewriteMap examplemap txt:/path/to/file/map.txt
You would then be able to use this map in a RewriteRule as follows:
RewriteRule ^/ex/(.*) ${examplemap:$1}
3) Advanced Rewrites Filesystem Reorganization Description:
This really is a hardcore example: a killer application which heavily uses
per-directory RewriteRules to get a smooth look and feel on the Web while
its data structure is never touched or adjusted.
drwxrwxr-x 2 netsw users 512 Aug 3 18:39 Audio/
drwxrwxr-x 2 netsw users 512 Jul 9 14:37 Benchmark/
drwxrwxr-x 12 netsw users 512 Jul 9 00:34 Crypto/
drwxrwxr-x 5 netsw users 512 Jul 9 00:41 Database/
drwxrwxr-x 4 netsw users 512 Jul 30 19:25 Dicts/
drwxrwxr-x 10 netsw users 512 Jul 9 01:54 Graphic/
drwxrwxr-x 5 netsw users 512 Jul 9 01:58 Hackers/
drwxrwxr-x 8 netsw users 512 Jul 9 03:19 InfoSys/
drwxrwxr-x 3 netsw users 512 Jul 9 03:21 Math/
drwxrwxr-x 3 netsw users 512 Jul 9 03:24 Misc/
drwxrwxr-x 9 netsw users 512 Aug 1 16:33 Network/
drwxrwxr-x 2 netsw users 512 Jul 9 05:53 Office/
drwxrwxr-x 7 netsw users 512 Jul 9 09:24 SoftEng/
drwxrwxr-x 7 netsw users 512 Jul 9 12:17 System/
drwxrwxr-x 12 netsw users 512 Aug 3 20:15 Typesetting/
drwxrwxr-x 10 netsw users 512 Jul 9 14:08 X11/
Solution:
The solution has two parts: The first is a set of CGI scripts which create
all the pages at all directory levels on-the-fly. I put them under
/e/netsw/.www/ as follows:
-rw-r--r-- 1 netsw users 1318 Aug 1 18:10 .wwwacl
drwxr-xr-x 18 netsw users 512 Aug 5 15:51 DATA/
-rw-rw-rw- 1 netsw users 372982 Aug 5 16:35 LOGFILE
-rw-r--r-- 1 netsw users 659 Aug 4 09:27 TODO
-rw-r--r-- 1 netsw users 5697 Aug 1 18:01 netsw-about.html
-rwxr-xr-x 1 netsw users 579 Aug 2 10:33 netsw-access.pl
-rwxr-xr-x 1 netsw users 1532 Aug 1 17:35 netsw-changes.cgi
-rwxr-xr-x 1 netsw users 2866 Aug 5 14:49 netsw-home.cgi
drwxr-xr-x 2 netsw users 512 Jul 8 23:47 netsw-img/
-rwxr-xr-x 1 netsw users 24050 Aug 5 15:49 netsw-lsdir.cgi
-rwxr-xr-x 1 netsw users 1589 Aug 3 18:43 netsw-search.cgi
-rwxr-xr-x 1 netsw users 1885 Aug 1 17:41 netsw-tree.cgi
-rw-r--r-- 1 netsw users 234 Jul 30 16:35 netsw-unlimit.lst
The DATA/ subdirectory holds the above directory structure, i.e. the real *
net.sw* stuff and gets automatically updated via rdist from time to time.
The second part of the problem remains: how to link these two structures
together into one smooth-looking URL tree? We want to hide the
DATA/directory from the user while running the appropriate CGI scripts
for the
various URLs. Here is the solution: first I put the following into the
per-directory configuration file in the
DocumentRoot<http://httpd.apache.org/docs/2.0/mod/core.html#documentroot>of
the server to rewrite the announced URL
/net.sw/ to the internal path /e/netsw:
RewriteRule ^net.sw$ net.sw/ [R]
RewriteRule ^net.sw/(.*)$ e/netsw/$1
The first rule is for requests which miss the trailing slash! The second
rule does the real thing. And then comes the killer configuration which
stays in the per-directory config file /e/netsw/.www/.wwwacl:
Options ExecCGI FollowSymLinks Includes MultiViews
RewriteEngine on
# we are reached via /net.sw/ prefix
RewriteBase /net.sw/
# first we rewrite the root dir to
# the handling cgi script
RewriteRule ^$ netsw-home.cgi [L]
RewriteRule ^index\.html$ netsw-home.cgi [L]
# strip out the subdirs when
# the browser requests us from perdir pages
RewriteRule ^.+/(netsw-[^/]+/.+)$ $1 [L]
# and now break the rewriting for local files
RewriteRule ^netsw-home\.cgi.* - [L]
RewriteRule ^netsw-changes\.cgi.* - [L]
RewriteRule ^netsw-search\.cgi.* - [L]
RewriteRule ^netsw-tree\.cgi$ - [L]
RewriteRule ^netsw-about\.html$ - [L]
RewriteRule ^netsw-img/.*$ - [L]
# anything else is a subdir which gets handled
# by another cgi script
RewriteRule !^netsw-lsdir\.cgi.* - [C]
RewriteRule (.*) netsw-lsdir.cgi/$1
Some hints for interpretation:
1. Notice the L (last) flag and no substitution field ('-') in the forth
part
2. Notice the ! (not) character and the C (chain) flag at the first rule
in the last part
3. Notice the catch-all pattern in the last rule
Reference: http://httpd.apache.org/docs/2.0/misc/rewriteguide.html (SEE
also the excellent sections on blocking annoying robots, and other tricks).
4) I would consider organizing your blog files into some form of
organization like say an Alphabetical new file structure where wildcard
rewrites will reduce your toital number of rewrites.
With a large number of rewrites, especially where are permanent R1 redirect
is used, I would ALWAYS USE HARD /etc/apache2 configuration files as an
include statement. They are easier to backup manage, grep through and
evaluate problems after a graceful restart to reinitialize new changes.
>
>> Thank you for your feedback.
>>
>> ------------------------
>> Keith Smith
>>
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