[jira] [Created] (JCR-4049) BLOBInTempFile deletes underlying file before it can be used

["Ray Navarette (JIRA)" <ji...@apache.org>]

Ray Navarette created JCR-4049:
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             Summary: BLOBInTempFile deletes underlying file before it can be used
                 Key: JCR-4049
                 URL: https://issues.apache.org/jira/browse/JCR-4049
             Project: Jackrabbit Content Repository
          Issue Type: Bug
          Components: jackrabbit-core
    Affects Versions: 2.12.1
            Reporter: Ray Navarette


Consider the following:
{code}
InputStream in = node.getProperty(name).getBinary().getStream();
Object result = processTheStream(in);  // IOException sometimes thrown
{code}
When a BLOBInTempFile is is no longer referenced, its finalizer deletes the underlying temp file.  However, an InputStream created from Binary.getStream() may still be in use and the deletion causes an IOException to be thrown.  I didn't see anywhere in the javadoc mention that the reference to a given Binary object would need to be retained in order for the underlying stream to still be valid, so this seems to be a side effect of the specific implementation in its handling of the temp file cleanup.

This issue can be difficult to track down due to the fact that garbage collection plays a role in when the references are cleaned and hence when the files are deleted.

I believe either of these options would be sufficient to fix the problem:
1) Update BLOBInTempFile.getStream() to return an InputStream implementation that maintains a reference to the BLOBInTempFile object that creates it.  This way there is a valid reference to the BLOBInTempFile object until the input stream itself goes out of scope, preventing the file from being prematurely deleted.  I've done this at the application level as a hack by extending FilterInputStream and maintaining an unused reference to the Binary, and this solution seems to do the trick.
2) Update BLOBInTempFile finalizer to _not_ delete the underlying file.  This may not be sufficient in the case where the file is not constructed by the TransientFileFactory, but the actual usage may cover this case.  If we know the temp file was properly created though, it should be cleaned as all other temp files are when there are no more references.  This would mean that the reference held in the InputStream would be sufficient to keep the file in existence until it was used, even if the BLOBInTempFile was no longer in scope.



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