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From "Dave Marion (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-3555) TabletServerBatchReaderIterator doesn't maintain reference to TabletServerBatchReader
Date Tue, 03 Feb 2015 17:29:35 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-3555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14303644#comment-14303644
] 

Dave Marion commented on ACCUMULO-3555:
---------------------------------------

The reference to the TSBR is passed to the TSBRI, but it then copied in the constructor and
discarded. If it was not a copy, then in next() when hasNext() is false, you could call close()
on the reference.

I would suggest that most of the examples so far are basic and could be covered with a try-with-resources
statement. I would also say that there are more advanced uses of BatchScanner in which you
don't want it to AUTOCLOSE. I have not looked through the code enough, but maybe if the BatchScanner
were created like the following, then you could use the logic I mentioned above.

{code}
BatchScanner bs = conn.createBatchScanner(tableName, Authorizations.EMPTY, 4, BatchScanner.AUTOCLOSE);
{code}

> TabletServerBatchReaderIterator doesn't maintain reference to TabletServerBatchReader
> -------------------------------------------------------------------------------------
>
>                 Key: ACCUMULO-3555
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3555
>             Project: Accumulo
>          Issue Type: Bug
>          Components: client
>    Affects Versions: 1.5.0, 1.5.1, 1.5.2, 1.6.0, 1.6.1
>            Reporter: Josh Elser
>            Assignee: Josh Elser
>            Priority: Blocker
>
> Had a user in IRC run into this again today upgrading a 1.4 instance to 1.6.0.
> ACCUMULO-587 introduced a {{finalize}} implementation into {{TabletServerBatchReader}}
in an attempt to close the {{BatchScanner}} when the user might have forgotten to do so themselves.
The problem, however, is that the {{TabletServerBatchReaderIterator}} doesn't maintain a reference
to the {{TabletServerBatchReader}} (notice how it only uses it to create a new instnace of
{{ScannerOptions}} using the copy constructor).
> In other words, when the {{TabletServerBatchReaderIterator}} is constructed, it has no
references in the object graph to the {{TabletServerBatchReader}} it was created from. This
means that if clients don't hold onto the BatchScanner instance, it's possible that it gets
closed by the JVM calling {{finalize()}}.



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