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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 45104] New: Possible Thread Safety Problem in FOP 0.93
Date Fri, 30 May 2008 18:02:31 GMT
https://issues.apache.org/bugzilla/show_bug.cgi?id=45104

           Summary: Possible Thread Safety Problem in FOP 0.93
           Product: XMLGraphicsCommons
           Version: Trunk
          Platform: Other
        OS/Version: other
            Status: NEW
          Severity: normal
          Priority: P2
         Component: XMP
        AssignedTo: general@xmlgraphics.apache.org
        ReportedBy: lulich.john@aoins.com


Please forgive me, I'm a Java developer, not a System Administrator. 
Information I'm providing regarding our systems is to the best of my current
knowledge.

Production Environment:
Server: IBM WebSphere Application Server v5.1
Platform: IBM S/390
OS: z/OS
FOP 0.93
Java 1.4

Development Environment:
Computer: Intel Core2 Duo CPU E4500@2.20GHz
2.19GHz, 2.98 GB RAM
OS: Windows XP Professional, 2002, SP2
IDE: WebSphere Developer for System Z (WDz) v.7.0.1
Server: WebSphere v5.1 Test Environment

On your site,
http://xmlgraphics.apache.org/fop/0.94/embedding.html#multithreading, you
write:  <If you encounter any suspicious behaviour, please notify us.>

Here's my suspicious behavior:

We have been running FOP 0.93 since upgrading in March of 2007.  In late
February/Early March of 2008, we began receiving a VERY low frequency of
reports from users informing us that when they attempt to print PDF documents
from our site, they are receiving complete documents for a different customer. 
If they close the PDF and generate it again, they get the correct documents. 
So far in 2008, we have 15 incidents reported out of roughly 260,000 hits to
this process.

We initially assumed that we had a multi-threading problem in our Java code,
but after careful review and testing, we determined that is not the case.  We
have been running this same Java code with only minor base read changes for
nearly three years without similar incident.  Also, our logging process has
never captured an error that we could tie to this problem in any way. 
Likewise, our general server logs also come up clean.

We have noticed that the majority of these problems have occurred when our
mainframe CPU's are getting pushed to (or near) 100%, but some have occurred
during timeframes when a spike was not detected (though our tracking tools may
not have caught it, since spikes are only logged if they last for a specified
amount of time).

Unfortunately, we cannot duplicate this problem at will, either on our
mainframe or in our development environment.  Past mainframe load tests have
not shown any problems.  The few multi-thread issues we have encountered in
code we have written for other projects has been easily found, and we have
other programming groups using the same basic Java/JAXB process to gather data
and marshall XML--the only difference being that they have switched over to
using Crystal Reports to convert the XML to PDF, and this project is the last
one still using FOP.  Consequently, we are the only ones running into this
problem.

Your statement: "Apache FOP may currently not be completely thread safe" raises
some red flags with us.  I'm sorry I can't provide better detail at this time,
but as I said, the only evidence of a problem comes in the form of a user's
call to tech support, and a faxed or emailed copy of the pdf.

Thanks for your help,
John Lulich


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