general load balancing issues

[Adam C. Migus]

On Monday 15 December 2003 08:02 am, Clement Laforet wrote:
> On Mon, 15 Dec 2003 12:46:52 +0100
> Bogdan TARU <bgd at icomag.de> wrote:
>
> Hi !
>
> >  Right now I am considering a setup with one common NFS repository
> > for the configuration files, Apache binaries, Web content and temp
> > directory for PHP, NFS resource which will be mounted on all the
> > 'front' webservers. I am wondering, though, if I will be able (by
> > having one common temp directory for PHP) to load-balance the
> > domains involving sessions: will the sessions be lost when
> > connsecutive hits go to different webservers, or not?
>
> If I were you, I would consider a 3-tier architecture
>
>
>                   /----------+
>                  /           |
>                 /        +-------+
>     +----------+         |  web  |        +----------+
> ----|   Load   |         |servers|--------|NFS server|
>
>     | balancer |         |  pool |        +----------+
>
>     +----------+         |       |
>                 \        +-------+
>                  \           |
>                   \----------+
>
> Concerning PHP session, a HTTP reverse-proxy can easily do the trick.
> If you don't want to spend a lot of time on configuring apache as
> reverse proxy, you can use some flexible and easy-to-use dedicated
> software.
> Here's my favorite:
> 1. pound (${PORTSDIR}/www/pound}
> pound can handle URI based sessions to redirect request to the
> correct backend server. It support SSL too.
>
> 2. haproxy (${PORTSDIR}/net/haproxy)
> haproxy is less intuitive than pound, but more flexible.
> It DOES NOT support SSL.
>
> Both support backend failures.
> Since thay acts like proxy, you don't have to reconfigure your
> network (but I recommend it)
>
> To grab real IP address on your apache server you must use (and
> configure carefully) mod_extract_forwarded{2} or mod_rpaf{2}.
>
> If you don't want to use a reverse proxy, Matthew Seaman's solution
> looks the best.
>
>
> clem

I'd be willing to bet the database back-end solution is going to
perform a lot better than a shared directory.  With respect to the 
reverse-proxy approach, it doesn't sound like it has clear advantage 
over the database back-end approach.  It's certainly a cool way to do 
it especially if you weren't doing database stuff.  Since your going 
for performance, already using a database and doing a new 
configuration, my vote is for the database back-end solution as well.

Adam