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From Simone Gianni <simo...@apache.org>
Subject Re: Streaming BLOB/LOB : who closes the stream?
Date Sat, 11 Apr 2009 13:58:04 GMT
Hi Ignacio,
That would mean that :
- when the setter returns, OpenJPA has consumer the stream and I can  
close it. This is obviously not the case, to act that way the content  
should be buffered, making the whole streaming system useless.  
Otherwise I have to keep a reference to each stream I used, and close  
it after the transaction has finished, which is again quite a problem  
cause I could have no way to know when the transaction ends.

- to make it symmetric, following what David say, OpenJPA or the jdbc  
driver should close the stream retrived by the application calling a  
getter, seems like this is not the case, at least not with mysql.

While I do understand the concern of not closing a stream cause it  
could be reused, I don't fully understand how it applies to OpenJpa,  
cause the stream is anyway consumed to the end. Moreover there are a  
number of techniques to avoid stream closing (wrap it overriding the  
close method) which are by far simpler than closing the stream when  
the (potentially distributed) transaction ends.

Wdyt?

Simone

Inviato da iPhone

Il giorno 10/apr/09, alle ore 17:06, Ignacio Andreu  
<plunchete@gmail.com> ha scritto:

> Hi Simone,
>
> As David said, close the stream is not the business of the  
> framework, if you
> open the stream you should close it. Maybe we should put a note in the
> documentation.
>
> Thanks,
>
> On Fri, Apr 10, 2009 at 2:47 AM, David Jencks  
> <david_jencks@yahoo.com>wrote:
>
>>
>> On Apr 9, 2009, at 10:18 AM, Simone Gianni wrote:
>>
>> Hi all,
>>> I noticed that when using streaming BLOB, after consuming the  
>>> stream,
>>> OpenJPA does not close it. This is causing lots of problems to us,  
>>> cause
>>> we're working on a system that needs to populate lots of blobs  
>>> from incoming
>>> files, submit them to a number of "processors" and then save them  
>>> back to
>>> file system storage. Since the FileInputStream we are passing to  
>>> OpenJPA
>>> during the "fetch" phase never gets closed, after a few seconds  
>>> the system
>>> runs out of resources.
>>>
>>> Ignacio, can you confirm this is the case?
>>>
>>> Since once the stream is used it is (99% of the times) unusable  
>>> again,
>>> OpenJPA should close it in the DBDictionary class, eventually in  
>>> the method
>>> that consumes it (it should be copy(InputStream,OutputStream) IIRC).
>>>
>>> Documentation says nothing about the need to hold a reference to the
>>> stream passed to a bean to close it after OpenJPA finished using  
>>> it, and I
>>> think it would be quite a pain to close the streams from the  
>>> application
>>> layer, cause that would mean keeping a reference to them. In plain  
>>> english,
>>> the contract should be something like "If you call the getter and  
>>> obtain an
>>> input stream, it's your job to close it, if you call a setter  
>>> passing an
>>> input stream, it's OpenJPA job to close it".
>>>
>>> I'm testing right now a patch (3 lines) to close it after OpenJPA  
>>> used it.
>>> If I'm not missing something and you agree this is a bug, I'll  
>>> open an issue
>>> and attach the patch to it to keep track of the problem.
>>>
>>
>> I tend to disagree with you about the design and think whoever  
>> opens the
>> stream should be responsible for closing it.  I've repeatedly had  
>> to work
>> around the behavior you are advocating as implemented in IIRC  
>> xerces. IIRC
>> the situation I keep running into is an input stream from a jar  
>> entry where
>> closing the input stream closes the entire jar file.  In order to  
>> use xerces
>> we had to wrap the input stream from the jar entry in something  
>> that ignores
>> the close method.  This experience has convinced me that something  
>> that
>> reads from a supplied input stream has no business deciding whether  
>> to close
>> it.
>>
>> thanks
>> david jencks
>>
>>
>>
>>>
>>> Simone
>>>
>>> --
>>> Simone Gianni            CEO Semeru s.r.l.           Apache  
>>> Committer
>>> http://www.simonegianni.it/
>>>
>>>
>>
>
>
> -- 
> Blog: http://plunchete.wordpress.com/
> Web Page: http://es.debugmodeon.com/

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