[prev in list] [next in list] [prev in thread] [next in thread] 

List:       backhand-users
Subject:    Re: [m_b_users] redirecting on overload
From:       Theo Schlossnagle <jesus () omniti ! com>
Date:       2002-04-25 13:59:14
[Download RAW message or body]

Petr Prazak wrote:

>I have a specific question about configuration of mod_bh.
>
>On my site, I have a web server and a cluster of file servers. From
>the web server I redirect requests for specific files to the file
>servers. I'd like to setup the mod_bh of the servers to better
>distribute the load of the file servers (now it is done as a dns
>round-robin).
>
>However, I'd like to have an option to redirect request to a different
>site (Akamai) if all file servers are busy (or overloaded, according to
>candidacy functions).
>
>I think a special candidacy function would be needed. Am I right ?
>
I'll prefix this by saying thatI haven't looked at the 
HTTPRedirectByName code since I wrote it :-)

Well.  I think I would write my own candidacy function to do exactly 
what I wanted, but I bet you can get something working with the existing 
functions.  If you were running your own CDN, or used ont that didn't 
manipulate the URL, you could use something like:

Backhand HTTPRedirectToName images.%1H

However, if you are using akamai, or some such beast, you need to munge 
the URL.  I would write it all in one candidacy funciont that changes 
the request uri and sets the new hostname for redirect too.  You can 
steal it mostly from the HTTPRedirectByName code.  You want the hostname 
to simply be rewritten to something like: a160.g.akamaitech.net and the 
request rewritten with the same sort of %S and %H stuff as the 
HTTPRedirectToName supports.  /images/pixel.gif would nee dto become 
something like:

/3/160/31/9/%0H/images/pixel.gif

(which %0H would expand to the full Host: header of the request).

I am _sure_ that this can be done with backhand and mod_rewrite 
together, but my rewrite kung fu is inferior.

You could solve this by aliasing /3/160/31/9/www.example.com/images/ to 
/images/  on your server and then blanket rewrite every image that 
arrives like that.  Then you really only need to swap out the host and 
not change the URI at all.

Enough ideas... I will stop rambling now.

-- 
Theo Schlossnagle
Principal Consultant
OmniTI Computer Consulting, Inc. -- http://www.omniti.com/
Phone:  +1 301 776 6376       Fax:  +1 410 880 4879
1024D/82844984/95FD 30F1 489E 4613 F22E  491A 7E88 364C 8284 4984
2047R/33131B65/71 F7 95 64 49 76 5D BA  3D 90 B9 9F BE 27 24 E7




_______________________________________________
backhand-users mailing list
backhand-users@lists.backhand.org
http://lists.backhand.org/mailman/listinfo/backhand-users
[prev in list] [next in list] [prev in thread] [next in thread]