On Thu, 2003-11-13 at 23:44, Sam Varshavchik wrote:
> Andrew Ingram writes:
> 
> > There is one change we have made to SqWebmail's core, that was to remove
> > the strcmp checking of the session id, this was to enable multiple
> > logins onto the same mailbox.
> 
> Oh, that's nice.  Now two people log in, see that there's new mail in INBOX, 
> open the INBOX simultaneously, each process then attempts to build the new 
> folder index, and cheerfully scribbles over each other's index file.
> 
> Occasional, mysterious, random failures is exactly what I expect to happen.
> 
> >                               This has been running fine for a few
> > months and I dont think this is the culperate here, since I have logs of
> > when users are logging on and can clearly see that these users have had
> > premature timeouts.
> 
> I can see exactly how this would be the result, every once in a while.
> 
> To summarize, each request updates the timestamp file.  If one request is in 
> the middle of updating the timestamp file, while the other process just 
> happens to check the timestamp file, then the check will fail; the second 
> process will conclude that the timestamp is not valid, and kick out the 
> login.
> 
> Or, if one of the logins obediently clicks on the logout link, instead of 
> shutting down the browser, various files are going to be removed, and the 
> next request from the other login will fail.
> 
> I can go on, and on, and on…

Aha. Thanks for the tips. We did do quite a bit of testing on this
feature and did not experience any problems like you suggest, but I see
from your description that it is entirely possible, and is obviously
dependent on the exact timings of things. 

What I will do is go back to the logs and try and work out if both these
users had multiple logins at the same time. I will report back with the
information.
Regards,
Andrew




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