high availability web service infrastructure: your experiences?

[Apologies to those who received this via LITA-L a few weeks
ago.]

We are embarking on a redesign of our Library IT
infrastructure, and I'm
looking into our web site/service architecture.  My redesign
goals
include:

 * Improving the availability of web delivered services

 * Introducing a development -> staging -> production
flow for content
and applications

 * Providing a flexible architecture that can accommodate
new (and
unanticipated!) projects

 * Doing this all while spending as little money as possible


While I'm an "old hand" at software, I am but a
novice in the library
world and would benefit greatly from your experiences.

So, I would like to tap into the community's experience in
building
*high availability* web systems for libraries.  I realize
that is a bit
of a broad brush inquiry, so here are some specific
questions that may
give you a better idea of what I'm after, specifically about
high
availability systems:

  * What sort of high availability architecture do you use? 
(e.g.,
clustering, load balancing, etc.)  What is the scope of
your
architecture? (e.g., web server, application server,
database, etc.)

  * If clustering or load balancing, how do you distribute
your web
content to your servers? (e.g., replication/mirroring,
network file
system, global file system, etc.)

  * How do you move your content/applications through
development/staging/production?  (e.g., home grown tools,
version
control system, content management system, etc.)

  * Do you use a content management system in a high
availability
configuration?  Any quirks, words of wisdom, etc.?

Thanks very much!


Tom Wood
thomas.a.wooduconn.edu
ITS Applications Developer
University of Connecticut Libraries

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On Jan 31, 2007, at 11:25 AM, Tom Wood wrote:

Tom,

I am curious why this would be any different from any other
(non- 
library) environment. A highly available webserver is the
same  
regardless of where -no?  Embracing
the 'no silver bullet  
philosophy I will share my experience with this in a none
library  
environment and with any luck it will help or at worst guide
you on  
what not to do.


>   * What sort of high availability architecture do you
use?  (e.g.,
> clustering, load balancing, etc.)  What is the scope of
your
> architecture? (e.g., web server, application server,
database, etc.)
>
>   * If clustering or load balancing, how do you
distribute your web
> content to your servers? (e.g., replication/mirroring,
network file
> system, global file system, etc.)
>
>   * How do you move your content/applications through
> development/staging/production?  (e.g., home grown
tools, version
> control system, content management system, etc.)
>
>   * Do you use a content management system in a high
availability
> configuration?  Any quirks, words of wisdom, etc.?

For our purposes we chose CARP on three servers. HTTP is
stateless so  
YMMV. I shared the load with round-robin in DNS to provide
failover.  
This is not perfect but it works for. For instance I can
imagine  
server one going down and still receiving hits. Still I
don't think  
about this choice that much.  (You may
though.)

We installed

http://www.backhan
d.org/wackamole/

This is still further complicated with the Apache logs
(minor  
complication but a complication nonetheless.)

So we live with a combination of cronjobs + rsync to make
sure all  
servers remain mirrored.

I cannot recall why we didn't choose the Linux Virtual
Server project.

http://www.linuxvi
rtualserver.org/

which seems to have active development and will probably
address most  
of your needs above.

regards,
./fxk

===============
Francis Kayiwa
Library Systems Team
4-180, MC 234
T: +1.312.996.2716
W: http://www.uic.edu/~kayiwa

Key: http://tigge
r.uic.edu/~kayiwa/kayiwa.gpg


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