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Date: Sun, 30 Sep 2007 12:02:51 -0700 (PDT)
From: "Hoss Man (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-1011) Two or more writers over NFS can
 cause index corruption
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    [ https://issues.apache.org/jira/browse/LUCENE-1011?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12531368 ] 

Hoss Man commented on LUCENE-1011:
----------------------------------

: In testing in my NFS area (mix of Linux & OS X), I see
: NativeFSLockFactory sometimes (rarely) allowing a lock to be
: double-acquired.  Whereas after stress testing SimpleFSLockFactory for
: a looong time, it never allows that.
: 
: So the NFS challenge/saga continues: now, you should in fact use
: SimpleFSLockFactory, and work around the fact that you will sometimes
: have to manually remove lock files (it is the lesser of evils).

i'm not an expert on file Locking (either in Lucene, or in the JVM, or any OSes) but i have to wonder if the problems you are seeing are inherent in the Java FileLock APIs, or if they only manifest in specific implementations (ie: certain JVM impls, certain filesystems, certain combinations of NFS client/server, etc...)

if we can say "NativeFSLockFactory uses the Java FileLock API to provide locking.  FileLock known to be buggy in the following situations: .... " then we've done all we can do, correct?

> Two or more writers over NFS can cause index corruption
> -------------------------------------------------------
>
>                 Key: LUCENE-1011
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1011
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Index
>    Affects Versions: 1.9, 2.0.0, 2.0.1, 2.1, 2.2, 2.3, 2.4, 2.9
>            Reporter: Michael McCandless
>            Assignee: Michael McCandless
>            Priority: Minor
>             Fix For: 2.3
>
>         Attachments: LUCENE-1011.patch
>
>
> When an index is used over NFS, and, more than one machine can be a
> writer such that they swap roles quickly, it's possible for the index
> to become corrupt if the NFS client directory cache is stale.
> Not all NFS clients will show this.  Very recent versions of Linux's
> NFS client do not seem to show the issue, yet, slightly older ones do,
> and the latest Mac OS X one does as well.
> I've been working with Patrick Kimber, who provided a standalone test
> showing the problem (thank you Patrick!).  This came out of this
> thread:
>   http://www.gossamer-threads.com/lists/engine?do=post_view_flat;post=50680;page=1;sb=post_latest_reply;so=ASC;mh=25;list=lucene
> Note that the first issue in that discussion has been resolved
> (LUCENE-948).  This is a new issue.

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