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From "Michael McCandless (JIRA)" <>
Subject [jira] Commented: (LUCENE-1877) Improve IndexWriter javadoc on locking
Date Sun, 30 Aug 2009 20:25:32 GMT


Michael McCandless commented on LUCENE-1877:

bq. Anyone remember why NativeFSLockFactory is not the default over SimpleFSLockFactory?

In my testing (long ago) over NFS, I actually found "native" locks didn't work as well as
"simple" locks.  I was also a bit nervous on how well supported "native" locks are across
different OSs. 

bq. My preference would really be to make it the default (though of course not for 2.9).

+1, I think it's the better default.

People who use Lucene over NFS already have to do special things (eg make a custom deletion
policy), and far too many users hit the "leftover lock file" problem.  We could state in the
javadocs that this default will change in 3.0?

Maybe just add one sentence in that IndexWriter locking section, referencing the discussion
in NativeFSLockFactory's javadocs about not having the "leftover lock file" problem?

> Improve IndexWriter javadoc on locking
> --------------------------------------
>                 Key: LUCENE-1877
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Javadocs
>            Reporter: Mark Miller
>            Priority: Trivial
>             Fix For: 2.9
> A user requested we add a note in IndexWriter alerting the availability of NativeFSLockFactory
(allowing you to avoid retaining locks on abnormal jvm exit). Seems reasonable to me - we
want users to be able to easily stumble upon this class. The below code looks like a good
spot to add a note - could also improve whats there a bit - opening an IndexWriter does not
necessarily create a lock file - that would depend on the LockFactory used.
> {code}  <p>Opening an <code>IndexWriter</code> creates a lock file
for the directory in use. Trying to open
>   another <code>IndexWriter</code> on the same directory will lead to a
>   {@link LockObtainFailedException}. The {@link LockObtainFailedException}
>   is also thrown if an IndexReader on the same directory is used to delete documents
>   from the index.</p>{code}
> Anyone remember why NativeFSLockFactory is not the default over SimpleFSLockFactory?

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