[Zope] Password screens

[Michel Pelletier]

> -----Original Message-----
> From: Andreas Kostyrka [mailto:andreas@mtg.co.at]
> Sent: Wednesday, July 07, 1999 3:42 PM
> To: Michel Pelletier
> Cc: 'John Eikenberry'; zope@zope.org
> Subject: RE: [Zope] Password screens
> 
> 
> On Wed, 7 Jul 1999, Michel Pelletier wrote:
> > Chris is still evaluating this question.  We'll let you 
> know as soon as
> > we know.  On a similar note, there will be a handful of DAs that we
> > support, all others will be continue to be unsupported, and probably
> > unthreadsafe unless someone patched them up.
> So what DAs are being supported by DC?
> 

We'll let you (meaning everybody) know as soon as we know.

> Unthreadsafe DAs could be a performance bottleneck, but then, 
> one usually
> could serialize the requests to two backend connections, right?
> (Because each Z SQL method is a seperate transaction in SQL 
> speak, right?)
> 

I don't think so, I believe the problem lies in that many of the
database client libraries reference global data.  If two threads enter
that code at the same time, even if they are using different
connections, they will step on each others concept of 'their' global
data.  This problem can exist at any point from the DA down to the C
code that the database client library may be written in (if it's written
in C, gadfly's client interface, for example, is written entirely in
Python).

-Michel

> Andreas
> -- 
> Win95: n., A huge annoying boot virus that causes random 
> spontaneous system
>      crashes, usually just before saving a massive project.  
> Easily cured by
>      UNIX.  See also MS-DOS, IBM-DOS, DR-DOS, Win 3.x, Win98.
> 
> 
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