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https://issues.apache.org/jira/browse/LUCENE-1044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12547217
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Michael McCandless commented on LUCENE-1044:
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>From java-dev, Robert Engels wrote:
{quote}
My reading of the Unix specification shows it should work (the _commit under
Windows is less clear, and since Windows is not inode based, there may be
different issues).
http://www.opengroup.org/onlinepubs/007908799/xsh/fsync.html
{quote}
OK thanks Robert.
I think very likely this approach (let's call it "sync after close")
will work. The _commit docs (for WIN32) also seems to indicate that
the file referenced by the descriptor is fully flushed (as we want):
http://msdn2.microsoft.com/en-us/library/17618685
Also at least PostgreSQL and Berkeley DB "trust" _commit as the
equivalent of fsync (though I have no idea if they use it the same way
we want to).
Though ... I am also a bit concerned about opening files for writing
that we had already previously closed. It arguably makes Lucene "not
quite" write-once. And, we may need a retry loop on syncing because
on Windows, various tools might wake up and peek into a file right
after we close them, possibly interfering w/ our reopening/syncing.
I think the alternative ("sync before close") is something like:
* Add a new method IndexOutput.close(boolean doSync)
* When a merge finishes, it must close all of its files with
doSync=true; and write the new segments_N with doSync=true.
* To implement commit() ... I think we'd have to force a merge of
all written segments that were not sync'd. And on closing the
writer we'd call commit(). This is obviously non-ideal because
you can get very different sized level 1 segments out. Although
the cost would be contained since it's only up to mergeFactor
level 0 segments that we will merge.
OK ... I'm leaning towards sticking with "sync after close", so I'll
keep coding up this approach for now.
> Behavior on hard power shutdown
> -------------------------------
>
> Key: LUCENE-1044
> URL: https://issues.apache.org/jira/browse/LUCENE-1044
> Project: Lucene - Java
> Issue Type: Bug
> Components: Index
> Environment: Windows Server 2003, Standard Edition, Sun Hotspot Java
> 1.5
> Reporter: venkat rangan
> Assignee: Michael McCandless
> Fix For: 2.3
>
> Attachments: FSyncPerfTest.java, LUCENE-1044.patch,
> LUCENE-1044.take2.patch, LUCENE-1044.take3.patch, LUCENE-1044.take4.patch
>
>
> When indexing a large number of documents, upon a hard power failure (e.g.
> pull the power cord), the index seems to get corrupted. We start a Java
> application as an Windows Service, and feed it documents. In some cases
> (after an index size of 1.7GB, with 30-40 index segment .cfs files) , the
> following is observed.
> The 'segments' file contains only zeros. Its size is 265 bytes - all bytes
> are zeros.
> The 'deleted' file also contains only zeros. Its size is 85 bytes - all bytes
> are zeros.
> Before corruption, the segments file and deleted file appear to be correct.
> After this corruption, the index is corrupted and lost.
> This is a problem observed in Lucene 1.4.3. We are not able to upgrade our
> customer deployments to 1.9 or later version, but would be happy to back-port
> a patch, if the patch is small enough and if this problem is already solved.
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