Re: [Lurker-users] Lurker 2 feedback and various questions

[Julian M. <ju...@me...>]

Wesley & Jonas,

five years ago I wrote in this thread ...

  http://www.terpstra.ca/lurker/message/20060426.192614.7b0ef322.en.html :

> The Apache 2 docs have to say the following about per-directory
> RewriteRules:
> 
> | Unbelievably mod_rewrite provides URL manipulations in per-directory
> | context, i.e., within .htaccess files, although these are reached a
> | very long time after the URLs have been translated to filenames. It
> | has to be this way because .htaccess files live in the filesystem, so
> | processing has already reached this stage. In other words: According
> | to the API phases at this time it is too late for any URL
> | manipulations. To overcome this chicken and egg problem mod_rewrite
> | uses a trick: When you manipulate a URL/filename in per-directory
> | context mod_rewrite first rewrites the filename back to its
> | corresponding URL (which is usually impossible, but see the
> | RewriteBase directive below for the trick to achieve this) and then
> | initiates a new internal sub-request with the new URL. This restarts
> | processing of the API phases.
> |
> | Again mod_rewrite tries hard to make this complicated step totally
> | transparent to the user, but you should remember here: While URL
> | manipulations in per-server context are really fast and efficient,
> | per-directory rewrites are slow and inefficient due to this chicken
> | and egg problem. But on the other hand this is the only way
> | mod_rewrite can provide (locally restricted) URL manipulations to the
> | average user.
> 
> That's why I'd like to avoid them.
> 
> I researched the issue, and in a per-server RewriteRule,
> %{REQUEST_FILENAME} oddly does NOT contain the filename as mapped by
> the "/lurker" Alias, but only the URI path, e.g. "/lurker/splash/index
> .en.html".  It seems that the Alias is NOT processed before the
> per-server RewriteRule.
> 
> So as far as I can see, the following is the only way to avoid a per-
> directory RewriteRule.  Note that I have split the /var/www/lurker
> frontend cache into several caches into /var/lib/lurker/www/<frontend>.
> 
>   ScriptAliasMatch ^/lurker/((lurker|jump|keyword|bounce)\.cgi)$ /usr/lib/cgi-bin/lurker/$1
>   Alias /lurker /var/lib/lurker/www/<frontend>
>   RewriteCond /var/lib/lurker/www/<frontend>/$1 !-s
>   RewriteRule \
>     ^/lurker/((attach|list|mbox|message|mindex|search|splash|thread|zap)/[^/]+)$ \
>     /lurker/lurker.cgi \
>     [L,PT,E=LURKER_CONFIG:/etc/lurker/lurker.conf,E=LURKER_FRONTEND:/var/lib/lurker/www/<frontend>/$1]
> 
> Does anyone know a nicer way to avoid a per-directory RewriteRule?

I have now figured out how to avoid having to specify the frontend path
more than once and also avoid a per-directory RewriteRule (and thus the
performance penalty):

  ScriptAlias /lurker-cgi/ /usr/lib/cgi-bin/lurker/

  RewriteRule ^/lurker/(.*)$ - \
    [E=LURKER_CONFIG:/etc/lurker/lurker.conf,E=LURKER_FRONTEND:/var/lib/lurker/www/<frontend>/$1]
  RewriteCond %{ENV:LURKER_FRONTEND} !-s
  RewriteRule ^/lurker/(attach|list|mbox|message|mindex|search|splash|thread|zap)/[^/]+$ /lurker-cgi/lurker.cgi [L,PT]
  RewriteRule ^/lurker/ %{ENV:LURKER_FRONTEND} [L]

Feel free to add that to Lurker's docs and/or apache.conf.

-Julian