[Zope-dev] Re: [ZODB-Dev] Re: BTrees strangeness (was Zope 2.X BIG Session problems - blocker - our site dies - need help of experience Zope developer, please)

[Steve Jibson]

Good morning.

I just got in and checked on my customer's system.  In the past 22 1/2 
hours they've had 15000 page hits and last night at about 9:30, ONE 
person got a KeyError.  Actually, this same person got twenty KeyErrors 
over a period of about 45 seconds.  I'm downloading their log files now 
and plan to spend some time this morning going through them.

Anyway, it appears that I was wrong when I said that the problem doesn't 
show up when I use FileStorage (although it does seem to happen less 
frequently -- but who can be sure of anything at this point?).

In answer to your questions earlier, Chris, we set up the user session 
at login time because we make the user answer some questions at login 
time that determine which portions of the interface to present to 
him/her.  For example, using the same login id and password, a user may 
choose to login as an administrator or as a normal user.  We store this 
choice and other info based on this choice in the session.  Also, we 
don't rely on the browser to time out the authentication cookie.  Once a 
user authenticates with ExUserFolder, ExUserFolder keeps their 
credentials in a cache until they have been inactive for 10 minutes (the 
timer resets with each cache hit).  If their credentials are not in the 
cache, rather than looking them up again, the user is logged out and 
must re-authenticate.  It seems like a reasonable way to handle logins 
and sessions.

In addition to going through log files, I will spend some more time 
today making sure we're not doing something stupid in our app.

Thanks again (to Chris, Michael, Alex and everyone else who has lost 
sleep over this session stuff).  I'll keep you posted on any new 
information I find.

Steve

Chris McDonough wrote:
> On Mon, 2004-05-17 at 23:08, Chris McDonough wrote:
> 
>>There indeed is a minor off-by-one error: it manifests itself as
>>sessions timing out at most 20 seconds early.
>>
>>But there is also a deeper issue which involves the fact that a session
>>data object is not properly removed from an older bucket when it "moves"
>>due to being accessed in a later timeslice; the symptom only appears
>>when a browser id is "reused" to start a session after it was used to
>>start an older one that had timed out normally.  I've got almost no clue
>>why this happens at this point, but I'm working on it.  Ugh.  This is
>>almost certainly what Steve is experiencing.
> 
> 
> I take that back.  Actually, I think I was just reading the test results
> and debug output wrong.  It appears to be operating normally except for
> the off-by-one problem (which is minor).  I need to jack up the tests to
> do some comparisons of data values; currently I'm just testing to ensure
> that *something* is in the session.. I need to test if the "right" thing
> is in the session over time.
> 
> - C
> 
> 
> 
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