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https://issues.apache.org/jira/browse/LUCENE-5904?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14113528#comment-14113528
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Michael McCandless commented on LUCENE-5904:
--------------------------------------------
To summarize this issue:
First Rob added nice new evilness to MDW so that sometimes Directory.deleteFile
would fail even if Lucene did not have that file open, simulating a virus
checker temporarily holding the file open. (Previously this operation would
always succeed).
But this new evilness uncovered a nasty corruption case in Lucene, whereby 1)
an unclean shutdown of a previous IW left some "future" segment files in the
index, e.g. _5.pos, 2) the new IW starts up and identifies this file as not
being referenced and immediately tries to delete it, but 3) the virus checker
prevents _5.pos being deleted on init. Normally this is "ok": IW records that
this file needs deleting but failed last time and so it periodically retries.
The problem is, when the IW goes and flushes a few segments, it may now in fact
overwrite _5.pos with a "real" one, which may succeed (if virus checker is done
with that file), and then later when IW retries its deletes, it removes _5.pos,
corrupting the index.
I don't know of any actual user cases showing this corruption case ... but it's
quite insidious ...
> Add MDW.enableVirusScanner / fix windows handling bugs
> ------------------------------------------------------
>
> Key: LUCENE-5904
> URL: https://issues.apache.org/jira/browse/LUCENE-5904
> Project: Lucene - Core
> Issue Type: Bug
> Reporter: Robert Muir
> Attachments: LUCENE-5904.patch, LUCENE-5904.patch, LUCENE-5904.patch,
> LUCENE-5904.patch, LUCENE-5904.patch, LUCENE-5904.patch
>
>
> IndexWriter has logic to handle the case where it can't delete a file (it
> puts in a retry list and indexfiledeleter will periodically retry, you can
> force this retry with deletePendingFiles).
> But from what I can tell, this logic is incomplete, e.g. its not properly
> handled during CFS creation, so if a file temporarily can't be deleted things
> like flush will fail.
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