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From "Michael Busch (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-669) finalize()-methods of FSDirectory.FSIndexInput and FSDirectory.FSIndexOutput try to close already closed file
Date Wed, 29 Nov 2006 06:09:25 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-669?page=comments#action_12454236 ] 
            
Michael Busch commented on LUCENE-669:
--------------------------------------

Mike,

I tried to add some debug to FSIndexOutput and made another observation which makes this issue
even odder! I added a boolean variable to FSIndexOutput with the name isOpen. I don't do anything
with this variable, I just change the close() method from:

  public void close() throws IOException {
    super.close();
    file.close();
  }

to 

  public void close() throws IOException {
    super.close();
    file.close();
    isOpen = false;
  }

and suddenly the problem disappears! Now I change close() to

  public void close() throws IOException {
    super.close();
    isOpen = false;
    file.close();
  }

and the IOException occurs again. Notice that I don't use isOpen anywhere else in the code.
So it seems that the problem only occurs if file.close() is the last instruction in close().
I bet this is a JVM bug, maybe the compiler makes some kind of optimization (maybe early freeing
up the resources of the method's context that are on the stack while the last instruction
of the method is being executed). So I'm not completely sure what the real problem is, but
I'm pretty sure it is a JVM bug.


> finalize()-methods of FSDirectory.FSIndexInput and FSDirectory.FSIndexOutput try to close
already closed file
> -------------------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-669
>                 URL: http://issues.apache.org/jira/browse/LUCENE-669
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Store
>            Reporter: Michael Busch
>         Assigned To: Michael Busch
>            Priority: Trivial
>         Attachments: FSDirectory_close_file2.patch
>
>
> Hi all,
> I found a small problem in FSDirectory: The finalize()-methods of FSDirectory.FSIndexInput
and FSDirectory.FSIndexOutput try to close the underlying file. This is not a problem unless
the file has been closed before by calling the close() method. If it has been closed before,
the finalize method throws an IOException saying that the file is already closed. Usually
this IOException would go unnoticed, because the GarbageCollector, which calls finalize(),
just eats it. However, if I use the Eclipse debugger the execution of my code will always
be suspended when this exception is thrown.
> Even though this exception probably won't cause problems during normal execution of Lucene,
the code becomes cleaner if we apply this small patch. Might this IOException also have a
performance impact, if it is thrown very frequently?
> I attached the patch which applies cleanly on the current svn HEAD. All testcases pass
and I verfied with the Eclipse debugger that the IOException is not longer thrown.

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