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From "Simon Helsen (JIRA)" <>
Subject [jira] [Commented] (JENA-91) extremely large buffer is being created in ObjectFileStorage
Date Mon, 22 Aug 2011 21:42:29 GMT


Simon Helsen commented on JENA-91:

Paolo, I am trying to debug/dig into the code to see if I can make sense of why this concurrency
is failing. There is one thing I don't quite understand. In the begin$ method in the transaction
manager on line 319/320, I notice that if the transaction is READ, the components are always
empty, so, a READ transaction never really begins. A WRITE transaction seems to start the
begin fine. Is this how it is supposed to be? I was trying to understand why the components
may be empty, but I didn't see through the long change of embedded objects. Just thoughts,
perhaps it helps you

I do think however, that with the patched TestTransSystem (which only has 1 read and 1 write
thread), it should be easier to debug the problem. 

> extremely large buffer is being created in ObjectFileStorage
> ------------------------------------------------------------
>                 Key: JENA-91
>                 URL:
>             Project: Jena
>          Issue Type: Bug
>          Components: TDB
>            Reporter: Simon Helsen
>            Assignee: Andy Seaborne
>            Priority: Critical
>         Attachments: TestTransSystem.patch, TestTransSystem2.patch, TestTransSystem3.patch
> I tried to debug the OME and check why a bytebuffer is causing my native memory to explode
in almost no time. It all seems to happen in this bit of code in com.hp.hpl.jena.tdb.base.objectfile.ObjectFileStorage
(lines 243 onwards)
>   // No - it's in the underlying file storage.
>         lengthBuffer.clear() ;
>         int x =, loc) ;
>         if ( x != 4 )
>             throw new FileException(""+loc+")["+filesize+"]["+file.size()+"]:
Failed to read the length : got "+x+" bytes") ;
>         int len = lengthBuffer.getInt(0) ;
>         ByteBuffer bb = ByteBuffer.allocate(len) ;
> My debugger shows that x==4. It also shows the lengthBuffer has the following content:
[111, 110, 61, 95]. This amounts to the value of len=1869495647, which is rather a lot :-)
Obviously, the next statement (ByteBuffer.allocate) causes the OME.

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