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Posted to dev@poi.apache.org by Christopher Cudennec <cu...@24translate.de> on 2009/06/22 15:15:44 UTC

Concurrency issues in EscherProperties

Hi everybody! 

  

We’re using poi-3.5-beta5-20090219.jar and have concurrency problems within EscherProperties (interpreting the stacktrace). Two threads try to read a Word document at the same time but end up in a deadlock. When searching for the problem using Google a came up with a similar ticket for Confluence: http://63.246.22.60/browse/CONF-15826 . Do you use a similar code base? 

  

Cheers, 

  

Christopher

AW: Concurrency issues in EscherProperties

Posted by Christopher Cudennec <cu...@24translate.de>.

Hi Josh,

thanks for fixing the issue :) We'll integrate a new release as soon as possible!

Christopher

-----Ursprüngliche Nachricht-----
Von: Josh Micich [mailto:josh.micich@gmail.com] 
Gesendet: Dienstag, 23. Juni 2009 20:16
An: POI Developers List
Betreff: Re: Concurrency issues in EscherProperties

Hello Christopher,
Thanks for the link, there was enough information there to identify the bug.

This has now been fixed on trunk.  Here is the bugzilla entry:
https://issues.apache.org/bugzilla/show_bug.cgi?id=47412

If you have the stack-trace, it's probably still worth posting, so other
people with the same problem can find this thread more easily.

cheers,
Josh


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Re: Concurrency issues in EscherProperties

Posted by Josh Micich <jo...@gmail.com>.

Hello Christopher,
Thanks for the link, there was enough information there to identify the bug.

This has now been fixed on trunk.  Here is the bugzilla entry:
https://issues.apache.org/bugzilla/show_bug.cgi?id=47412

If you have the stack-trace, it's probably still worth posting, so other
people with the same problem can find this thread more easily.

cheers,
Josh

AW: Concurrency issues in EscherProperties

Posted by Christopher Cudennec <cu...@24translate.de>.

Hello Josh,

Thank you for your answer. You can have a look at the link that I posted by viewing a version from Google's cache ;) - http://209.85.129.132/search?q=cache:I-ejIOo-xEgJ:63.246.22.60/browse/CONF-15826+escherproperties+concurrent&cd=1&hl=de&ct=clnk&gl=de&client=firefox-a (try "escherproperties concurrent" with Google).

We got the concurrent issue when reading a document. I'll try to send a proper stacktrace or code sample to reproduce the error. You mentioned non-obvious internal side-effects: That corresponds to the link that I gave you above.

Thanks,

Christopher

-----Ursprüngliche Nachricht-----
Von: Josh Micich [mailto:josh.micich@gmail.com]
Gesendet: Montag, 22. Juni 2009 19:35
An: POI Developers List
Betreff: Re: Concurrency issues in EscherProperties

Hello Christopher,

For the most part, POI does not support multi-threaded access to
object instances. This issue is not well addressed in the
documentation, but I guess a simple rule would be that as long as all
threads perform read operations, concurrent access should be
supported. If you are having concurrency problems, it probably means
that at least one of your threads has changed common data. The
offending data modification may obvious from the external API, in
which case it's probably best for the client code to manage
synchronization. On the other hand, the external API methods you are
calling may look 'read only' but have some non-obvious internal
side-effect (like lazy initialisation), and in this case POI should
probably be synchronized internally to manage this.

There is not enough information to diagnose your problem. The link
you posted is protected. Please post the relevant stack trace(s)
and/or some sample code the reproduces the bug.

regards,
Josh

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Re: Concurrency issues in EscherProperties

Posted by Josh Micich <jo...@gmail.com>.

Hello Christopher,

For the most part, POI does not support multi-threaded access to
object instances. This issue is not well addressed in the
documentation, but I guess a simple rule would be that as long as all
threads perform read operations, concurrent access should be
supported.  If you are having concurrency problems, it probably means
that at least one of your threads has changed common data.  The
offending data modification may obvious from the external API, in
which case it's probably best for the client code to manage
synchronization.  On the other hand, the external API methods you are
calling may look 'read only' but have some non-obvious internal
side-effect (like lazy initialisation), and in this case POI should
probably be synchronized internally to manage this.

There is not enough information to diagnose your problem.  The link
you posted is protected.  Please post the relevant stack trace(s)
and/or some sample code the reproduces the bug.


regards,
Josh

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