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From "Ryan Ackley" <sack...@cfl.rr.com>
Subject Re: Locking up Application Server when creating new HSSFWorkbook
Date Fri, 09 Jan 2004 16:10:19 GMT
This sounds like a threading issue in you app. POI may be making the problem
more visible because it sounds like its taking some time to complete.

-Ryan

----- Original Message ----- 
From: <Pat.Klein@moorewallace.com>
To: <poi-user@jakarta.apache.org>
Sent: Friday, January 09, 2004 9:41 AM
Subject: RE: Locking up Application Server when creating new HSSFWorkbook


> We have tried most of the suggestions provided without luck (and thanks
for
> the responses).  Garbage collection appears to be functioning fine.  CPU
> utilization remains low.  As we have been testing this more, one
interesting
> thing that we have found is that other user requests to the server will
> eventually be processed while the HSSFWorkbook is being instantiated but
not
> in a timely manner.  In other words, if I open 2 browsers and start the
part
> that uses POI the application will appear to hang to the second browser.
> But a request made by the 2nd browser while the app seems to be hung will
> eventually come back before the POI piece completes in the first browser.
>
> More info on our environment - 1 WAS 5.0.1 running on Linux, JRE 1.3.1.
>
> -----Original Message-----
> From: Michael Zalewski <zalewski@optonline.net
> <mailto:zalewski@optonline.net> >@MOORECORP
> Sent: Wednesday, January 07, 2004 7:44 PM
> To: Klein, Pat (WTC/Lisle)
> Subject: RE: Locking up Application Server when creating new HSSFWorkbook
>
>
> If the Admin Console also hangs up, that is a sign that something else is
> going on. The Admin server runs in a separate JVM, so it won't be as
> severely impacted by garbage collection on your web application. The Admin
> Console still runs, even if a Web Application Server is entirely locked
up.
> However, a large amount of garbage collection may slow the admin console
> down to a crawl, because of 100% CPU utilization, especially under Windows
> single processor systems.
>
> Is your server running on Windows? And are there multiple processors?
> Another possibility might be that requests fail to get processed because
of
> network I/O. Garbage collection might cause worse lockups of the admin
> console if only a single processor.
>
> What version of Websphere? Probably 4.0? If 5.0 or 5.1, you might consider
> acoliver's suggestion of using a newer JRE for your web application. If
you
> are using 4.0, you can use only JRE up to 1.3 I believe. But parallel
> garbage collection will not help much if your admin console (separate JVM)
> is also locking up.
>
> When you turn performance monitoring on, look to see if there are
*several*
> garbage collection sweeps made in between the instantiation of
HSSFWorkbook
> and the next line. (I assume you are reading a large workbook - This is
> exactly the problem case for POI on a web server environment).
>
> -----Original Message-----
> From: Pat.Klein@moorewallace.com <mailto:Pat.Klein@moorewallace.com>
> [mailto:Pat.Klein@moorewallace.com]
> <mailto:[mailto:Pat.Klein@moorewallace.com]>
> Sent: Wednesday, January 07, 2004 9:04 AM
> To: zalewski@optonline.net <mailto:zalewski@optonline.net>
> Subject: RE: Locking up Application Server when creating new HSSFWorkbook
>
> Thanks for the response.  When the server hangs,everythingrunning on
> Websphere hangs- adminconsole and all.  We have been able to trace the
> moment of hang up to the instantiation of the HSSFWorkbook.
> We are currently using the internal HTTP server andlockups can be
duplicated
> everytime we run a large excel file.  I will try turning on the tracing
and
> see what I see.
> Thanks...
> -----Original Message-----
> From: Michael Zalewski <zalewski@optonline.net
> <mailto:zalewski@optonline.net> >@MOORECORP
> Sent: Tuesday, January 06, 2004 7:12 PM
> To: POI Users List
> Subject: RE: Locking up Application Server when creating new HSSFWorkbook
> I have also had similar problems (Websphere 4.0). I think in my case it
was
> because of an excessive number of objects being created and destroyed
(i.e.,
> garbage collection tool several seconds). But I never fully diagnosed the
> problem (And I am not even sure that the problem was due to POI).
> I don't know what you mean when you say 'Websphere app server hangs up'.
Do
> you mean that there is no response from the admin console? No response
from
> any servlet? Or just no response from the servlet that creates a
> HSSFWorkbook? Do you have a load balanced environment? Could session
> serialization be a problem? (Are you putting the HSSFWorkbook into a
> HttpSession, and letting Websphere try to persist the session?) Are you
> trying to send a large spreadsheet to the client with https?
> You could try the following:
> 1) Use Websphere's own internal HTTP Server, instead of
Apache/IIS/Netscape
> 2) Lower the amount of heap memory used. See if that makes the lockups
more
> frequent.
> 3) Turn on Garbage Collection tracing. See if generating the HSSFWorkbook
> causes many sweeps.
> I think that Garbage Collection is the most likely culprit. (A JVM can do
> very little while a garbage collection is in process. That would cause
your
> application to freeze. But the Admin Console and other application servers
> should continue to respond).
> If the problem is limited to a single servlet, you might also be
> synchronizing the servlet object on the request. For example, if there is
a
> servlet that implements SingleThreadModel, (or if you set it up that way
in
> web.xml), then subsequent requests for workbooks will appear to freeze
until
> the first workbook is completely downloaded.
> -----Original Message-----
> From: Pat.Klein@moorewallace.com <mailto:Pat.Klein@moorewallace.com>
> [mailto:Pat.Klein@moorewallace.com]
> <mailto:[mailto:Pat.Klein@moorewallace.com]>
> Sent: Tuesday, January 06, 2004 11:26 AM
> To: poi-user@jakarta.apache.org <mailto:poi-user@jakarta.apache.org>
> Subject: Locking up Application Server when creating new HSSFWorkbook
> We are running into a strange issue on our application.  When we are
> reading in an existing Excel spreadsheet (about 3.5 MB) and creating a
> new HSSFWorkbook, our entire WebSphere app server hangs up.  Once the
> workbook is created, all is well again.  As far as we can tell, there
> are plenty of system resources available (CPU and memory).  The POI
> version that we are using is 2.0 RC1.
>
> Anyone run into a similar problem?
>
> Thanks in advance...
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