StandardSessionManager(Thread-11): checking for idle sessions...

["christoph moar" <christoph.moar@xxxxxxxx>]

hi all,

i have this problem that keeps showing up, and i have not
yet found a solution for it:


we have a rather ingenious portal code running on enhydra,
this has been running fine for years. unfortunately, hardware
and software changes, including our last migration to enhydra-5.1
have produced a problem that i just cannot fix: from time to
time, our application debug log will show up the following
line

"StandardSessionManager(Thread-11): checking for idle sessions... "

and then nothing goes. the application simply hangs and i have
to restart multiserver.
the error happens non-deterministically, meaning i have not
found out really any situation or parameter that might make the error not
come up anymore.

i noticed that, most of the times, it happened when a robot/spider
would start navigating through our site (containing 10 tousands
of pages). our application has no problems with the load, since
we do a lot of internal database result caching, most of the
times we just have 1-3 db connections open, even with high load
on the web side we are able to deliver a lot of page with a low
load on the machine.

anyway, i can reproduce the error if i start about 7-8 recursive
"wget -r" processes on the portal page. then it'll take about
1-2 minutes and the application will hang again. the last thing
i see in the log file is, again, the above line with 
standardsessionmanager. 

but again, i can see that line many times before that, usually
followed by a "cleaning up idle session" and no problem at all.

StandardSessionManager(Thread-11): checking for idle sessions...
StandardSessionManager(Thread-11): cleaning up idle session:
e8iG7gucnhV7p4K7ldjR

i tried changing the session settings in the application log
file, currently i use

SessionManager.Lifetime = 0
SessionManager.SessionEncodeUrlState = Never
SessionHome.Mode = PAGE_TO_DISK
SessionHome.MaxSessions = -1
SessionHome.PageThreshold = 1000
SessionHome.PageTimeThreshold = 300
SessionHome.PageWait = 5
SessionHome.PageDir = /tmp/enhydrasessions

but i must admit i tried about any other setting as well.
in /tmp/enhydrasessions i do not see any file at all, in 
fact, when i start the seven concurrent wget processes, the
most that i get are 10-15 active sessions (counting that some
users are also navigating the site).

does please, please, anybody have a hint as to where this all
might lead? i have startet disallowing the robots to visit our
site (since then things are going better), but still had to
start "restarting" multiserver every morning now, but
still sometimes the error will show up during normal load on
the day. i really have to find a solution for this. i am using
enhydra-5.1-9 on fedora core 1 with apache httpd-2.0.50-1.0
and mod_proxy setting. the proxy makes sure all image and static
content is delivered by apache, only the presentation objects
will be delivered by enhydra.

maybe the error has nothing to do with the session? still, i must
admin, it's murphy: if the last thing i see in the log is the
line with sessionmanager, it should have something to do, right?

i must admin, i'm lost. i have increased logging to debug level,
verified that i do not have deadlocks on the database, did some
tuning to the conf files, still i have no clue as to what might
be the problem and how to inspect it.

i hope anybody has a hint for me,
thanks in advance
regards

christoph moar





--
http://www.alpin.it         software, consulting & strategy

Christoph Moar                          Dipl. Inform. Univ.
alpin gmbh srl          management & technology consultants
tel +39 0471 056007 fax +39 0471 056005 gsm +39 348 3057012
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http://www.alpin.it                 christoph.moar@xxxxxxxx