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From Joshua Chamas <jos...@chamas.com>
Subject Re: ANNOUNCE: Apache::ASP v1.93
Date Thu, 06 Jul 2000 00:10:45 GMT
Perrin Harkins wrote:
> 
> On Wed, 5 Jul 2000, Joshua Chamas wrote:
> > > This sounds interesting, but I don't quite understand what you did.  The
> > > sessions are stored in a dbm file, right?  Don't you still need locking if
> > > all servers are trying to update the same NFS-mounted dbm file?  Or am I
> > > totally off on how session storage is implemented?
> > >
> >
> > You might worry about this for concurrent writes to $Application,
> > or a framed application writing to $Session, so these are still
> > issues to worry about.
> 
> Okay, so I take it each user session is stored in a separate dbm file?

Yes.

> Then you still need reliable locking to prevent lost updates, but in
> practice $Session collisions are unlikely due to the separate files.
> 

Right.  Certainly not something you would trust a framed
site with ecommerce logic to but works in practice.

Note the SDBM_File is tolerant of concurrent writes, 
corruption free, even if you lose data, DB_File is not.
The session manager will always use SDBM_File internally
even when DB_File is specified for Session & Application.

At this time, I wouldn not recommend the use of $Application
in an NFS environment due to the lack of locking which is
critical to its proper use. 

-- Joshua
_________________________________________________________________
Joshua Chamas			        Chamas Enterprises Inc.
NodeWorks >> free web link monitoring	Huntington Beach, CA  USA 
http://www.nodeworks.com                1-714-625-4051

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